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F Unit guideCompounds and mixtures

Sheet 1 of 1© Harcourt Education Ltd 2004 Catalyst 2This worksheet may have been altered from the original on the CD-ROM.

Where this unit fits in Prior learningThis unit builds on:unit 8E Atoms and elements. Work on temperature, melting points and boiling points relates to unit 8IHeating and cooling.

The concepts in this unit are: compounds are materials formed by the combination and re-arrangement of different types of atoms duringa chemical reaction, the combination of the types of atom in a given compound is fixed, compounds havetheir own unique physical and chemical properties, the properties of mixtures are not constant.

This unit leads onto:unit 8G Rocks and weathering and unit 8H The rock cycle; (with unit 8E Atoms and elements) to unit 9EReactions of metals and metal compounds, unit 9F Patterns of reactivity, unit 9G Environmental chemistryand unit 9H Using chemistry.

This unit relates to:unit 7G Particle model of solids, liquids and gases and to unit 7H Solutions. However, if teachers wish tointroduce the idea of particles through unit 8E Atoms and elements, this unit could be taught before unit7G Particle model of solids, liquids and gases and unit 7H Solutions. Ideas in this unit about mixtures arepicked up in Consideration of air as a mixture relates to unit 8B Respiration and unit 9B Fit and healthy.

To make good progress, pupils startingthis unit need to: • name some elements • know that there are approximately 100

elements which are the building blocksfor all materials

• know that elements are composed oftiny particles called atoms

• know that compounds are formed whenatoms of different elements join

• have explored a number of chemicalreactions

• have made and separated mixtures.

Framework yearly teaching objectives – Particles• Compounds consist of fixed combinations of different types of atoms that cannot be easily separated. • Atoms and combinations of atoms can be represented by symbols and formulae. • Use the more sophisticated particle model to explain how chemical reactions take place.

Expectations from QCA Scheme of Work At the end of this unit …

… most pupils will … … some pupils will not have madeso much progress and will …

… some pupils will have progressed furtherand will …

in terms of scientific enquiry NC Programme of Study Sc1 1b; 2c, d, e, f, g, j, k

• make observations and measurements of mass andtemperature

• present results as line graphs and interpret these usingscientific knowledge and understanding.

• make observations and measurementsof mass and temperature

• with help, present these as linegraphs.

• explain how scales they chose for graphsenabled them to present results effectively

• make suggestions of additional work totest conclusions of their investigations.

in terms of materials and their properties NC Programme of Study Sc3 1a, b, e, f, g, h; 2h; 3h

• distinguish between elements, compounds and mixtures interms of the particles they contain

• name and describe some common mixtures and useknowledge about separation techniques to suggest howthey might be separated

• identify melting and boiling points as the fixed temperaturesat which elements and compounds change state, and use theparticle model to explain changes of state.

• name some common elements,compounds and mixtures anddistinguish between representations ormodels of these

• describe how some mixtures could beseparated

• recognise changes of state in elementsand compounds.

• explain their criteria for classifyingmaterials as elements, compounds ormixtures

• represent some compounds by formulaeand explain what these show about thenumbers and types of atom present

• describe how mixtures do not changestate at fixed temperatures.

Suggested lesson allocation (see individual lesson planning guides)Direct route

F1 Compounds allaround

F2 Reactingcompounds

F3 What’s in it?

F4 The air around us

F5 Formulae – Thinkabout ratios

Extra lessons (not in pupil book)

Review and assess progress(distributed appropriately)

MisconceptionsSome pupils associate the notion of pure with the idea of good or healthy rather than with a single substance. Pupils find it very difficult to giveexamples of mixtures or explain them because they tend to regard materials as single substances unless they can see the material consists of severalcomponents. Pupils frequently describe compounds as mixtures of elements.

Health and safety (see activity notes to inform risk assessment)Risk assessments are required for any hazardous activity. Special care must be taken when heating iron and sulphur and reacting ammonia withhydrogen chloride.

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F1Lesson planning

guideCompounds all around

Suggested alternative starter activities (5–10 minutes)

Introduce the unit

Unit map forCompounds andmixtures.

Learning objectivesi Recognise some compounds in everyday life. ii Compounds are very different from the elements that made them. iii The properties of pure substances, including melting points and boiling points.

Scientific enquiryiv Use first-hand observations and secondary data to draw conclusions. (Framework YTO Sc1 8d) v Describe how conclusions are consistent with the evidence obtained, using scientific knowledge and understanding to explain them. (Framework

YTO Sc1 7g)

Learning outcomes

Share learning objectives

• Describe how elements behave when they formcompounds.

• Explain how melting point and boiling point datacan be used to distinguish between elements.

• Be able to use melting point and boiling pointdata to distinguish between elements. (Sc1)

Problem solving

Pupils reviseparticlearrangementsassociated withelements andcompounds.

Capture interest (1)

Pupils look at images ofcrystals.Catalyst InteractivePresentations 2


Show pupils a videoclip of the reaction ofchlorine with sodium.Catalyst InteractivePresentations 2

Suggested alternative plenary activities (5–10 minutes)

Review learning

Pupils summarise evidencethey have to show that salt(sodium chloride) isdifferent from the elementsit contains.

Sharing responses

Pupils discuss interpretingobservations in Activity F1ain terms of what ishappening at particle/atomlevel and identifying theword equation.

Group feedback

Pupils discuss patterns indata from Activity F1b.

Word game

Pupils play odd man out.

Looking ahead

What evidence/clues wouldyou accept/look for thatshow a chemical reactionhas taken place?

Suggested alternative main activitiesActivity

Textbook F1

Activity F1a Practical

Activity F1b Paper

Activity F1c Catalyst Interactive Presentations 2

Learningobjectivesee above

i and ii

iv and v

iii, iv and v

ii

Description

Teacher-led explanation and questioning OR pupils work individually,in pairs or in small groups through the in-text questions and thenonto the end-of-spread questions if time allows.

Are compounds different from the elements in them? Pupils makeiron sulphide by heating a mixture of iron and sulphur then watch ademonstration of dilute sulphuric acid being added to the ironsulphide and to a mixture of iron and sulphur.

Melting points and boiling points Pupils answer questions aboutthe melting and boiling points of elements.

Support animation to reinforce understanding of the terms atom,molecule, element and compound.

Approx. timing

20 min

30 min

15 min

10 min

Target group

C H E S

R/G G R S

✔

✔ ✔ (✔ )

✔

Most pupils will …

• distinguish between elements and compoundsin terms of the particles they contain

• identify melting and boiling points as thefixed temperatures at which elements andcompounds change state

• use first hand and secondary data to showthat compounds are different from theelements that made them.

Some pupils, making less progress will …

• name some common elements, and compoundsand distinguish between representations ormodels of these

• recognise changes of state in elements andcompounds

• describe some differences between compoundsand the elements that made them.

Some pupils, making more progress will …

• also explain their criteria for classifyingmaterials as elements, or compounds.

Key wordshydrogen peroxide, pure

Out-of-lesson learningHomework F1 Textbook F1 end-of-spread questions

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F2Lesson planning

guideReacting compounds


Recap last lesson

Pupils play a quicktrue/false quiz.

Learning objectivesi When compounds react the atoms are rearranged. ii Recognise a chemical reaction.

Scientific enquiryiii Classify compounds into groups and different chemical reactions into types of reaction. iv Use first-hand observations and secondary data to draw conclusions. (Framework YTO Sc1 8d) v Describe how conclusions are consistent with the evidence obtained, using scientific knowledge and understanding to explain them. (Framework

YTO Sc1 7g) vi The hazards associated with different substances.

Learning outcomes


• Identify what evidence there is for achemical reaction taking place.

• Use ideas of particles to suggest whathappens to atoms in a chemical reaction.

• Be able to classify precipitation andcombustion as types of chemical reaction.

Problem solving

Pupils compare boiling waterwith calcium releasingbubbles when placed in waterand think about the ways inwhich these situations arethe same and different.


Demonstrate copperreacting with silvernitrate.


Demonstratemagnesium reactingwith HCl and releasingelectrical energysufficient for lighting alight bulb.


Review learning

Pupils present a summary ofwhat to advise a fellowpupil to look for to spot achemical change/reaction.

Sharing responses

Pupils discuss observationsin Activity F2a. Extend to looking at wordequations to representchanges.

Group feedback

Pupils discuss observationsfrom Activity F2b andevidence for chemicalchange. They suggest whatis happening in terms ofparticles and theirrearrangement.

Word game

Pupils piece together wordequations to representchemical reactionsdescribed.

Looking ahead

Pupils discuss the use ofthe term pure in everydaycontexts. They suggest whatthey understand by theterm pure using theirscience ideas.


Textbook F2


Activity F2b Practical

Activity F2c Catalyst Interactive Presentations 2


i, ii and iii

ii, iii, iv, vand vi

i, ii, iv, vand vi

i

Description


Collecting evidence for chemical reactions Pupils carry out andrecord observations of four chemical reactions.

Reacting ammonia with hydrogen chloride Demonstration to showpupils through the reaction between ammonia and hydrogen chloridethat pH can also indicate a chemical change.

Support animation of what happens in a chemical change.

Approx. timing

20 min

20 min

20 min

10 min

Target group

C H E S

R/G G R S

✔ ✔ (✔ )

✔ (✔ )

✔


• increase their knowledge of the range ofcompounds

• identify evidence to suggest a chemicalreaction is happening

• develop their familiarity with word equations.


• recognise more compounds • begin using word equations with more

confidence.

Some pupils, making more progresswill …

• also develop their understanding of howatoms are rearranged during reactionsinvolving compounds.

Key wordsreactants, products, precipitate




F3Lesson planning

guideWhat’s in it?


Recap last lesson

Pupils in pairsexplain themeanings of words.

Learning objectivesi The differences between mixtures and pure substances.

Scientific enquiryii Identify more than one strategy for investigating questions and recognise that one enquiry might yield stronger evidence than another.

(Framework YTO Sc1 8b) iii Recognise that a range of sources of information or data is required. (Framework YTO Sc1 8c) iv Draw conclusions from their own data and describe how their conclusions are consistent with the evidence obtained, using scientific knowledge

and understanding to explain them. (Framework YTO Sc1 8f)

Learning outcomes


• Be able to identify evidence to help distinguish amixture and a compound.

• Find out how the term pure is used by scientists. • Be able to use temperature data to help determine

the purity of water. (Sc1)

Problem solving

Pupils suggest whichseparating techniqueto use for givenexamples.

Capture interest

Teacher demo showingthermometer readings infunnel of crushed icefollowed by sprinklingsalt over the ice.

Brainstorming

Pupils are asked towrite down wordsthat may be waterrelated, e.g.aqueous, aquatic.


Review learning

Pupils produce their owndefinition of mixture.

Sharing responses

Pupils discuss graphs obtained from Activity F3aand what evidence this provides that impuritiesaffect the behaviour of a substance.

Group feedback

Pupils compare dataobtained in Activity F3b.

Word game

Pupils play bingo.

Looking ahead

What is the boilingpoint of air?


Textbook F3

Act F3a Practical

Activity F3b Paper

Activity F3c Catalyst InteractivePresentations 2


i, and ii

ii, iii and iv

ii, iii and iv

i

Description


A closer look at salty water Pupils compare what happens to thefreezing point of a sample of pure water with a sample containingdissolved salt.

The effect of salt on the boiling point of water Pupils see if saltcan affect the boiling point of water.

Support animation of distillation. Showing the behaviour of particlesfrom different constituents on reaching their boiling point.

Approx. timing

20 min

30 min

20 min

10 min

Target group

C H E S

R/G G R S

✔ (✔ )

✔ (✔ )

✔


• distinguish between compounds and mixtures• use knowledge about separation techniques to suggest

how they might be separated • realise that more than one approach may be needed to

answer a question • use data from more than one source to answer a

question • make measurements of temperature • present results as line graphs and interpret these using

scientific knowledge and understanding.

Some pupils, making less progresswill …

• distinguish between pure water and amixture that is mostly water

• describe how some mixtures could beseparated

• know that substances melt and freezeat a temperature that can be measured

• make measurements of temperature• with help, present these as line

graphs.


• realise that some lines of enquiry yieldstronger evidence than others

• also explain how scales they chose for graphsenabled them to present results effectively

• also describe how mixtures do not changestate at fixed temperatures

• recognise that a range of sources ofinformation or data is required to draw aconclusion.

Key wordsmixture, pure, red only: Fixed composition

Out-of-lesson learningHomework F3 Textbook F3 end-of-spread questions Pupils research how many different tests can be done on a sample ofurine for a variety of substances (protein, blood, pH) using 1 strip ofBayer tester.



F4Lesson planning

guideThe air around us


Recap last lesson

Pupils are asked to providethree facts/pieces ofinformation about mixtures.

Learning objectivesi Know about air as a mixture. ii Pure substances change state at fixed temperatures, mixtures do not.

Scientific enquiryiii Interpret evidence to support hypothesis (i.e. if we think we know what we mean by a compound and by a mixture how can we use

observations regarding air to classify it one way or the other). (Framework YTO Sc1 8a, f)

Learning outcomes

Share learningobjectives

• Find out how the term pure is used by scientists.

• Describe the effect ofcooling on air.

• Be able to usetemperature data toidentify pure substancesfrom mixtures. (Sc1)

Problem solving

Pupils are asked why watercreeps up an invertedmeasuring cylinder with ironfilings inside and why itdoesn’t creep upcompletely?


Photo or demo ofliquefaction of air or agiven gas being cooled.Catalyst InteractivePresentations 2


Pupils are shown a videoclip of liquid nitrogen.Catalyst InteractivePresentations 2


Review learning

Pupils sequence stages inthe liquefaction of air.

Sharing responses

Pupils summarise evidencefrom Activity F4a.

Group feedback

Pupils suggest what theywould expect if they usedsamples of air from differentsources in the experiment.

Word game

Check progress by playing aloop game reinforcing keywords from the unit.

Looking back

Pupils revise andconsolidate knowledge fromthe unit.


Textbook F4


Activity F4b Catalyst Interactive Presentations 2


i and ii

i and iii

i

Description


What’s in the air? Pupils observe the reaction as copper is heated in a fixed amount of air.

Support animation showing components in air.

Approx. timing

20 min

20 min

10 min

Target group

C H E S

R/G G R S

✔ (✔ )

✔

Key wordsnone



• distinguish between elements, compounds andmixtures in terms of the particles they contain

• realise that air from different sources will bedifferent, because air is a mixture.


• know more about air as a mixture • realise that air from different sources will be

different.


• also apply their knowledge about meltingpoints and boiling points to the fractionaldistillation of air.



F5Lesson planning

guideFormulae – Think about ratios


Bridging to the unit

Look at carbon monoxide andcarbon dioxide to show what isformed when too little oxygen isprovided. Illustrate with H2O2 andH2O the dangers of getting theratio incorrect.

Learning objectivesi Formulae and ratios. ii Use a model (mathematical) to interpret and predict the composition of compounds.The structure of this lesson is based around the CASE approach. The starter activities give concrete preparation. The main activities move away from theconcrete towards a challenging situation, where pupils need to think. The extended plenary gives pupils time to discuss what they have learnt, to negotiatea method to commit to paper and express their ideas verbally to the rest of the class.

Scientific enquiryiii Apply an understanding of ratios to chemical formulae. iv Interpret evidence to support hypothesis. (Framework YTO Sc1 8a) v Draw conclusions from data and describe how their conclusions are consistent with the evidence obtained, using scientific knowledge and

understanding to explain them (red only) (Framework YTO Sc1 8f) vi Consider whether the enquiry could have been improved to improve the accuracy. (Framework YTO Sc1 8g)

Learning outcomes

Setting the context

Introduce idea of chemical formulaas a scientist’s summary of theratio of substances needed toproduce a known compound.

Concrete preparation (1)

Use molymod or other models toillustrate how we can use theevidence from experiments todecide on chemical formulae.


Demo of electrolysis of water toshow fixed amounts of hydrogenand oxygen obtained.


Group Feedback

Pupils suggest a formula for one of the named compounds they met inActivity F5a.

Bridging to other topics

The class discusses and recaps other contexts in which fixed ratios areused.


Textbook F5

Activity F5a Paper

Activity F5b Practical


i and ii

i, ii, iii andiv

i, ii, iii, iv, v and vi

Description


What’s the ratio? Pupils identify the connection between thechemical formula of a compound and the ratio of the atomscontained in it.

Finding the composition of magnesium oxide Pupils find out howmuch magnesium and oxygen is present in the magnesium oxide theyproduce.

Approx. timing

20 min

20 min

30–40 min

Target group

C H E S

R/G G R S

✔

✔

Key wordsratio, red only: composition

Out-of-lesson learningTextbook F5 end-of-spread questions Pupils can research the discovery of penicillin and the identification ofchemical composition and/or the discovery of aspirin and identificationof chemical composition


• relate chemical formulae to the types ofatoms present in the compound

• relate chemical formulae to the ratio of thedifferent atoms present in the compound

• work out simple formulae • use formulae to work out the ratio of different

types of atom present in the compound.


• work out the types of atoms present in thecompound from the formulae

• with help, work out simple formulae.


• also work out more complex formulae • begin to understand that the ratio of the

different types of atom is not the same as theratio of the masses.


F Unit mapCompounds and mixtures


Copy the unit map and use these words to help you complete it.You may add words of your own too.

atomboiling pointchemical formulachemical reactionchemical symbolcompoundcrystaldistillationelementfixed composition Rfixed ratio Rhazard symbol

materialmelting pointmixturemoleculeparticlepHprecipitateproductspure substancereactantsword equations

Compoundsand mixtures

Chemicalformulae

Recognising compounds

Reactions ofcompounds

Mixtures

A closerlook at air

Unitmaps.qxd 12-Nov-03 8:56 AM Page 6


F1 StartersCompounds all around

Introduce the unit● Either draw the outline of the unit map on the board then ask

pupils to give you words to add, saying where to add them.Suggest some words yourself when necessary to keep pupils onthe right track.

● Or give out the unit map and ask pupils to work in groupsdeciding how to add the listed words to the diagram. Then gothrough it on the board as each group gives suggestions.

Share learning objectives● Ask pupils to write a list of FAQs they would put on a website

telling people about compounds using their ideas aboutparticles. Collect suggestions as a whole-class activity, steeringpupils towards those related to the objectives. Conclude byhighlighting the questions you want them to be able to answerat the end of the lesson.

Problem solving● Ask pupils in pairs to look at the diagrams of substances a–e on

the pupil sheet and for each one decide if it represents acompound or an element. They must be prepared to justifytheir choice.

● Alternatively cut up the diagrams and only give two or three toany one pair. After three minutes ask pairs with differentdiagrams to share their ideas.

● Ask pupils the following questions:

Which ones were difficult/easy to agree on? What clues didthey look for/use to make a decision? Are there any diagramswhich they cannot classify as a compound or an element? If so,why not? How would they describe these substances? What isdifferent about them?

Capture interest (1)● Show pupils crystal images of various elements/compounds.● What do they notice about their shapes? What does the shape

suggest about the organisation of the particles contained in thesubstance? How would these shapes compare to pieces of glassthat had been shattered?

Capture interest (2)● Pupils observe closely the video clip of the reaction of sodium

and chlorine and discuss what their observations suggest interms of changes taking place.

● Is this the only way a new substance can be made?

➔ Unit map

➔ Pupil sheet

Answersa: element (single atoms); b: element (diatomic molecules); c: compound; d: mixture of twodifferent elements; e: mixture ofelement and compound

➔ Catalyst Interactive Presentations 2


Observationssilvery solid (Na) ignites violently inyellow gas (Cl), gas and soliddisappear and a white powder forms(NaCl)


Introduce the unit

Unit map forCompounds andmixtures.


• Describe how elements behave when theyform compounds.

• Explain how melting point and boiling pointdata can be used to distinguish betweenelements.

• Be able to use melting point and boiling pointdata to distinguish between elements. (Sc1)

Problem solving

Pupils revise particlearrangements associatedwith elements andcompounds.


Pupils look at imagesof crystals.Catalyst InteractivePresentations 2


Show pupils a videoclip of the reaction ofchlorine with sodium.Catalyst InteractivePresentations 2

F-Starters.qxd 25-Nov-03 9:04 AM Page 1

F1 StartersCompounds all around

Problem solving

Here are some diagrams of the particles in different substances. Foreach one decide whether it is an element or compound. Be preparedto justify your choice.


a

b

c

d

e



F2 StartersReacting compounds

Recap last lesson● Ask pupils to decide whether the statements on the pupil sheet

are true or false. They must be prepared to support theiranswers.


telling people about chemical reactions. Collect suggestions as awhole-class activity, steering pupils towards those related to theobjectives.

● Conclude by highlighting the questions you want them to beable to answer at the end of the lesson.

Problem solving● In this activity pupils compare boiling water with calcium

releasing bubbles when placed in water and think about theways in which these situations are the same and different.


Give one way in which the examples are the same, and aredifferent.

What is happening to the particles of water when the water isboiling?

What evidence can you identify to show that the water has notchanged into a different substance?

If we test the bubbles from the water they contain water vapour.If we test the bubbles from the calcium we get a loud pop. Why?

What does this suggest is happening with the calcium and thewater?

Suggest a rule or guidance for someone to help them decidehow to interpret bubbles in an activity.

➔ Pupil sheet

Answerstrue: 1, 2, 4, and 5, false: 3


Recap last lesson

Pupils play a quicktrue/false quiz.


• Identify what evidence there is for a chemicalreaction taking place.

• Use ideas of particles to suggest whathappens to atoms in a chemical reaction.

• Be able to classify precipitation andcombustion as types of chemical reaction.(Sc1)

Problem solving

Pupils compare boilingwater with calciumreleasing bubbles whenplaced in water and thinkabout the ways in whichthese situations are thesame and different.


Demonstrate copperreacting with silvernitrate.


Demonstratemagnesium reactingwith HCl and releasingelectrical energysufficient for lighting alight bulb.



F2 StartersReacting compounds (continued)

Capture interest (1)● In this demonstration you will show that a chemical reaction

can take place without the need for heat or burning.

● Either place a very small square of copper foil in the middle ofa Petri dish and cover with drops of silver nitrate. View using adigital microscope.

● Or wrap a length of copper wire loosely around a pencil to forma copper coil or ‘caterpillar’, leaving a length of wire at each endof the coil to lower the copper into a beaker of silver nitratesolution. Observe.

● The copper metal displaces the silver from the silver nitrate andyou see very delicate silver crystals collecting around the coppermetal. The silver quickly oxidises and becomes grey.

● If you do the caterpillar version, with time you can detect theappearance of a pale green colour in the solution – coppernitrate.

● Tell the pupils the names of the chemicals, i.e. copper and silvernitrate. Ask pupils the questions on the right.

● Finish by saying that in the lesson they will be carrying outsome further chemical reactions of their own.

Capture interest (2)● In this demonstration you will show that a chemical change

has occurred through the transfer of electrical energy.

● Place the acid in the beaker. Connect the lamp to both pieces ofmetal using the crocodile leads and make sure it is clearlyvisible to the class. When ready, place both metals into the acid.

● The magnesium reacts with the acid and in doing so transferselectrical energy to the lamp which will shine until the reactionis complete. The copper is unaffected.

● Finish by saying that in the lesson they will be carrying outsome further chemical reactions of their own.

EquipmentEither Petri dish base, silver nitrate(very dilute solutions, e.g. 0.05 M,work fine), copper foil cut into 1cm2 piece

Or 250cm3 beaker, enough silvernitrate (very dilute solutions, e.g.0.05 M, work fine) to cover a loopof copper wire, 30cm length copperwire, pencil, safety goggles

QuestionsSuggest an explanation for whatyou are observing.

What is happening to the particlesof copper and particles of silvernitrate?

Is this reaction easily reversed?

Equipment250cm3 beaker, dilute HCl or 1Msulphuric acid, 10cm strip of cleanmagnesium ribbon, 10cm strip ofcopper foil, crocodile clips andleads, small bulb (1.5V)

QuestionsSuggest an explanation for whatyou are observing.

What is happening to the particlesof magnesium?

Where have they gone?

Is this reaction easily reversed?


F2 StartersReacting compounds

Recap last lesson

Look at the statements below and say whether they are true or false.

1 Iron sulphide is magnetic. true/false

2 Compounds contain atoms from at least two different elements. true/false

3 Glass is an example of a crystal. true/false

4 NaCl is the formula for sodium chloride. true/false

5 Melting point is the temperature at which a solid turns into a liquid. true/false




F3 StartersWhat’s in it?

Recap last lesson● Ask pupils to stand. Ask each, in turn, to explain the meaning

of a word. Pupils who give a correct explanation can sit down.

● Differentiate the words so that all pupils sit down after thesecond or third attempt. This can also be achieved by usingsome words more than once.


telling people about compounds and mixtures using their ideasabout atoms and molecules. Collect suggestions as a whole-classactivity, steering pupils towards those related to the objectives.Conclude by highlighting the questions you want them to beable to answer at the end of the lesson.

Problem solving● Pupils review previous work on separating techniques by

suggesting which technique to use for each example.


Describe the changes of state involved. What is the effect onthe particles of the separation, e.g. does the separation changethe iron and the salt particles?

Capture interest● In this demonstration pupils are asked to think about the

possibility that the properties of water can in some way beaffected by other chemicals such as salt and so lead into thepractical activity for the lesson.

● Set up the filter funnel containing crushed ice placed aroundthe base of a thermometer. Confirm with the class that thesteady temperature reading is 0°C as they would expect.Alternatively, use a temperature probe connected to a display.

● Sprinkle salt over the surface of the ice and observe thetemperature reading. Ask pupils to discuss their observations.Ask the questions on the right.

Brainstorming● Introduce aqua as the Latin word for water and say that this

stem is often in other water-related words, e.g. aquarium.

● Ask pupils first on their own to write down at least one otherword they can think of that may be a water-related wordbecause it contains the letters aqua.

● Now ask pupils to work in pairs and then fours to build up a listof words that are connected in some way with water.

Wordsmelting point, boiling point,compound, element, crystal,chemical formula, molecule, atom,mineral wool, hazard, puresubstance, precipitate, chemicalreaction, reactant, product, pH

➔ Pupil sheet

Equipmentlarge glass filter funnel, crushed ice,salt, long-stemmed thermometer oraccess to a temperature probe anddatalogger

QuestionsWhat changes have occurred? Howcould we show that these changesare definitely due to the salt? Whatwould you expect if we repeated theactivity?

EquipmentYou may find it useful to havedictionaries or a bank of words pre-prepared which pupils can thenlook up to see their connection withwater.


Recap last lesson

Pupils in pairs explainthe meanings of words.


• Be able to identify evidence to helpdistinguish a mixture and a compound.

• Find out how the term pure is used byscientists.

• Be able to use temperature data to helpdetermine the purity of water. (Sc1)

Problem solving

Pupils suggest whichseparating technique touse for given examples.

Capture interest

Teacher demo showingthermometer readings infunnel of crushed icefollowed by sprinklingsalt over the ice.

Brainstorming

Pupils are asked towrite down words thatmay be water related,e.g. aqueous, aquatic.


F3 StartersWhat’s in it?

Problem solving

Match each separation technique on the right to the correctexample of it on the left.


separating pure water from sea water

separating the pigments in paint

separating salt from water

separating iron from a beaker of salt and iron

separating components of blood

separating olive oil from water

separating gold from river bed silt

filtration

simple distillation

chromatography

evaporation

centrifuging

decanting

sieving

Extension



F4 StartersThe air around us

Recap last lesson● Ask three volunteers to come up to the front of the class. Ask

each in turn to speak for half a minute on the subject ofmixtures and how we can separate them to impress the classwith their knowledge.

● Have key words linked to mixtures and separating techniqueson the board that everyone can see as they come into class. Thenumber of words/ideas can be increased or reduced dependingon the class.

● The rest of the class take notes and at the end are asked to votefor the best show of knowledge. You could ask the contestantsto cast their own vote too.

● Round up by mentioning anything important that thecontestants omitted.


telling people about air. Collect suggestions as a whole-classactivity, steering pupils towards those related to the objectives.Conclude by highlighting the questions you want them to beable to answer at the end of the lesson.

Problem solving● Pupils work in pairs and look at the evidence on the pupil sheet

to offer explanations for what has been observed.

● The iron filings have slowly rusted using the oxygen contentfrom the sample of air trapped above the water, i.e. iron +oxygen → iron oxide. The water has replaced the oxygen andthere is a direct link between the increase in water level and theamount of oxygen present in the air sample.

Capture interest (1)● Pupils are shown a series of photos of the liquefaction of air and

are asked to discuss their observations. What evidence havethey now seen to suggest what the boiling point and freezingpoint of air is?

● How would they classify air – as a compound, element ormixture? What evidence do they have to support their choice?

Capture interest (2)● Pupils are shown a video clip of liquid nitrogen.

● They are asked to discuss their observations and summarise theproperties of nitrogen linked to its freezing and boiling points.

➔ Pupil sheet

HintsHow has the iron changed inappearance?

What chemical do you know thatalso produces the same reactionwith iron?

Some of the iron has not changed. Why not?




Recap last lesson

Pupils are asked toprovide threefacts/pieces ofinformation aboutmixtures.


• Find out how the term pure is usedby scientists.

• Describe the effect of cooling on air. • Be able to use temperature data to

identify pure substances frommixtures. (Sc1)

Problem solving

Pupils are asked why watercreeps up an invertedmeasuring cylinder withiron filings inside and whyit doesn’t creep upcompletely.


Photo or demo ofliquefaction of air or agiven gas being cooled.Catalyst InteractivePresentations 2


Pupils are shown a videoclip of liquid nitrogen.Catalyst InteractivePresentations 2


F4 StartersThe air around us

Problem solving

Sheet 1 of 1

Sheet 1 of 1

© Harcourt Education Ltd 2004 Catalyst 2This worksheet may have been altered from the original on the CD-ROM.

StartersF4 The air around us

Problem solving


iron filings

Before After

iron filings

iron filings

Before After

iron filings



F5 StartersFormulae – Think about

Bridging to the unit● Discuss with pupils evidence to show that compounds are different from mixtures.● Pupils look at evidence that compounds not only contain specific elements, but

that they must also be present in a fixed amount, which determines how thecompound behaves. Illustrate this by a) comparing the behaviour of water withhydrogen peroxide; b) comparing carbon dioxide with carbon monoxide; c) looking at samples of crystals.

● Show pupils real samples or photos of, e.g. sodium chloride, copper sulphate.Draw out the fact that the crystals each have a regular repeating shape but thatthese are different from each other. Ask pupils to suggest how this repeating shapeoccurs. Why are the crystals of sodium chloride the same shape but different sizes?

● Illustrate why scientists need to know what is the least amount of the elementthey can use to produce a given compound and so make what they intend to, bylinking to the drugs industry and the need for scientists to be able to repeatedlyproduce these compounds so that they can help counter diseases and illnesses.

Setting the context● Ask pupils to give you an example of a type of bread (i.e. leavened /unleavened

bread, pitta bread, bagels, naan, etc.). Summarise the responses, look at the rangeof breads and draw out the fact that there is no one ‘bread’ because bread is amixture and variations in colour, hardness, taste, etc. occur.

● Compare bread to a compound such as sodium chloride (salt) or water. Why isthere only one substance known as water? (Because it has a fixed composition inrelation to the starting materials.)

● Introduce the idea of ‘chemical formula’ as a scientist’s summary of the ratio ofingredients needed to produce a known compound. Show how this is differentfrom using a recipe for bread.

Concrete preparation (1)● Use molymod or other models to illustrate how we can use the evidence from

experiments to decide on the chemical formula or the ratio of ingredients neededto form water and so construct suggestions for how the various atoms are groupedtogether. These suggestions then help us to predict what to expect if thesecompounds then react with other known compounds.

Concrete preparation (2)● Demonstrate the Hoffmann Voltameter. Show how the electricity not only

provides us with evidence that water is a two-element compound but also that theelements hydrogen and oxygen are present in a fixed ratio.

● Confirm that the gases released are oxygen and hydrogen. Ask pupils to observethe volume readings in the voltameter. What pattern do they notice with thevalues?

● Work out the minimum ratio on the board using the data collected. Use models topresent visualisation of a basic water molecule.

● Ask pupils to predict what values they would expect for the following: a) 50cm3 ofoxygen present, ?cm3 of hydrogen present; b) ?cm3 of oxygen present, 30cm3 ofhydrogen present.

● Ask pupils to summarise the pattern in a statement/sentence.

➔ Teacher/Technician sheet

Answersa) 100cm3;b) 15cm3


Bridging to the unit

Look at carbon monoxide and carbon dioxideto show what is formed when too little oxygenis provided. Illustrate with H2O2 and H2O thedangers of getting the ratio incorrect.

Setting the context

Introduce idea of chemical formulaas a scientist’s summary of theratio of ingredients needed toproduce a known compound.


Use molymod or other modelsto illustrate how we can usethe evidence from experimentsto decide on chemical formulae.


Demo of electrolysis of waterto show fixed amounts ofhydrogen and oxygenobtained.


F5 StartersFormulae

Concrete preparation (2)Teacher/Technician sheetEquipment

● Hofmann voltameter containing distilled water which has been acidified with adrop of concentrated sulphuric acid

● 6V dc power supply● splints● matches● eye protection● cobalt chloride paper and/or anhydrous copper sulphate● pipette

● Top up the contents of the voltameter with distilled water in front of the class.(If you wish you can then use this water to test with the cobalt chloride paperand/or the anhydrous copper sulphate to show the presence of water.Remember, the tests only confirm the presence of water and don’t indicatepurity.)

● Collect and test each of the gas samples collected in the two arms and confirmthe presence of hydrogen and oxygen.

● Ask pupils to observe closely that the volume of hydrogen gas produced is twicethat of oxygen gas produced.


switch

battery

platinummetal

platinummetal

–

–

+

+

voltameter filledwith water


F1aTeacher

activity notesAre compounds different fromthe elements in them?

Running the activityPupils record the appearance of iron and sulphur. They heat a prepared mixture of iron and sulphur andrecord their observations. The teacher breaks a test tube and extracts some iron sulphide. The teacher addsa little dilute sulphuric acid to the iron and sulphur mixture and then to the iron sulphide. The gasesproduced are tested with a piece of filter paper soaked in lead nitrate solution.

Pupils do not need to know the details of the test for hydrogen sulphide with lead nitrate. The differencebetween the properties of a mixture of iron and sulphur and the properties of iron sulphide should beemphasised throughout this activity.

Other relevant materialSkill sheet 15: Word equations

Expected outcomesThe mixture in the test tube will start to glow, indicating that a chemical reaction is happening. The glowwill stop when the reaction is complete. If the mixture was well mixed and there was a slight excess ofsulphur, the lump of iron(II) sulphide made should not stick easily to a magnet. (The iron sulphide maystill be magnetic so try using poor quality magnets!)

PitfallsThere are safety risks if pupils mix their own samples of iron and sulphur. The prepared mixture should bewell mixed, because the iron filings settle to the bottom of the bottle. The iron(II) sulphide often becomesstuck in the bottom of the test tube. Ensure that the test tube is wrapped in newspaper before breaking itusing a mallet.

Safety notesEye protection must be worn. Heating iron and sulphur can cause the sulphur to burn with a blue flameproducing choking sulphur dioxide gas. Once the reaction has started, the test tube can be removed fromthe Bunsen burner flame to avoid this. A mineral wool plug reduces the chance of the sulphur vapourigniting.

The test tube should be broken carefully by the teacher and pieces of glass disposed of safely. Hydrogensulphide is highly toxic and should only be produced in the fume cupboard in very small amounts. Thetest tube should be washed out as soon as the tests have been carried out. Pieces of iron sulphide shouldnot be left in sinks.

AnswersCore:1 Yellow powder. 2 Shiny grey powder. 3 Black solid. 4 iron 5 Loss of yellow colour, change frompowder to solid lump. 6 The iron sulphide is not very magnetic. 7 A red glow inside the tube, maymention fumes. 8 No, hydrogen sulphide is only formed when you add dilute sulphuric acid to ironsulphide formed after heating, but not when it is added to the mixture of iron and sulphur.9 A magnet would remove iron from the mixture. 10 This would not easily work after the compound hasbeen formed. 11 The tube starts to glow as energy is given out to the surroundings during the reaction.12 iron + sulphur → iron sulphide. 13 Pupils’ drawings should show that the atoms of iron and sulphurthemselves do not change during the reaction, but that their arrangement does, i.e. separate atoms of ironand sulphur randomly arranged in the test tube before the reaction, and the same iron and sulphur atoms‘joined together’ in the test tube after the reaction.


Type Purpose DifferentiationPractical

Demonstration

Pupils heat iron and powdered sulphur to form iron sulphide. They consider theproperties of iron and sulphur before and after heating. Pupils watch a demonstration of dilute sulphuric acid being added to a mixture of ironand sulphur and then to the iron sulphide. They record their observations.Pupils use drawings to demonstrate what changes have occurred.

Core

F-Teachers.qxd 25-Nov-03 9:05 AM Page 1

F1aTechnician

activity notesAre compounds different fromthe elements in them?

Equipment neededFor the class:● four samples of powdered sulphur in sealed, transparent jars● four samples of iron filings in sealed, transparent jars● four magnets

For the teacher:● wooden mallet● two test tubes● newspaper● test tube rack● forceps● pieces of filter paper dipped into lead nitrate solution● dilute sulphuric acid (0.4mol/dm3)

For your informationRunning the activityPupils record the appearance of iron and sulphur. They heat a prepared mixture of iron and sulphur andrecord their observations. The teacher breaks a test tube and extracts some iron sulphide. The teacher addsa little dilute sulphuric acid to the iron and sulphur mixture and then to the iron sulphide. The gasesproduced are tested with a piece of filter paper soaked in lead nitrate solution.

Pupils do not need to know the details of the test for hydrogen sulphide with lead nitrate. The differencebetween the properties of a mixture of iron and sulphur and the properties of iron sulphide should beemphasised throughout this activity.


Expected outcomesThe mixture in the test tube will start to glow, indicating that a chemical reaction is happening. The glowwill stop when the reaction is complete. If the mixture was well mixed and there was a slight excess ofsulphur, the lump of iron(II) sulphide made should not stick easily to a magnet. (The iron sulphide maystill be magnetic so try using poor quality magnets!)

PitfallsThere are safety risks if pupils mix their own samples of iron and sulphur. The prepared mixture should bewell mixed, because the iron filings settle to the bottom of the bottle. The iron(II) sulphide often becomesstuck in the bottom of the test tube. Ensure that the test tube is wrapped in newspaper before breaking itusing a mallet.

Safety notesEye protection must be worn. Heating iron and sulphur can cause the sulphur to burn with a blue flame,producing choking sulphur dioxide gas. Once the reaction has started, the test tube can be removed fromthe Bunsen burner flame to avoid this. A mineral wool plug reduces the chance of the sulphur vapourigniting.

The test tube should be broken carefully by the teacher and pieces of glass disposed of safely. Hydrogensulphide is highly toxic and should only be produced in the fume cupboard in very small amounts. Thetest tube should be washed out as soon as the tests have been carried out. Pieces of iron sulphide shouldnot be left in sinks.


Type Purpose DifferentiationPractical

Demonstration

Pupils heat iron and powdered sulphur to form iron sulphide. They consider theproperties of iron and sulphur before and after heating.Pupils watch a demonstration of dilute sulphuric acid being added to a mixture of ironand sulphur and then to the iron sulphide. They record their observations.Pupils use drawings to demonstrate what changes have occurred.

Core

For each group:● disposable test tube (a combustion

tube) containing 0.5cm3 of aniron/sulphur mixture made frommixing 5g of iron filings with 3gof powdered sulphur, with a plugof mineral wool already placed inthe test tube

● test tube holder● Bunsen burner● heatproof mat

F-Technician.qxd 25-Nov-03 9:06 AM Page 1

F1aActivity

CoreAre compounds different fromthe elements in them?

You are going to make a sample of iron sulphide from iron andsulphur and compare its properties with those of iron andsulphur.

Equipment

● test tube containing iron and sulphur● test tube holder● Bunsen burner● heatproof mat

Obtaining evidence (1)

1 Heat the iron and sulphur as shown in the diagram.2 Point the open mouth of the tube away from yourself and

other pupils. Make sure you hold the bottom of the test tubein the hottest part of the Bunsen flame.

3 Heat for about 5 minutes or until you are convinced that thechemical reaction has taken place.

4 Place the test tube on the heatproof mat. Do not touch it for 10 minutes.

5 While your iron sulphide is cooling, look at the samples of iron,sulphur and the iron sulphide. Record your answers to thequestions below in a table.

Considering the evidence (1)

1 What does the sulphur look like?2 What does the iron look like?3 What does the iron sulphide look like?4 Which of the substances are magnetic?5 Write down one way in which the sulphur is different from the

iron sulphide.6 Write down one way in which the iron is different from the iron

sulphide.7 What did you see when the chemical reaction was happening?


Wear eyeprotection.

Take care!Iron filingsirritate the

skin. Make sure youdo not get them inyour eyes. Wash yourhands afterwards.

heat

mixture ofiron andsulphur

mineral wool

F-Activity.qxd 25-Nov-03 9:05 AM Page 1

F1aActivity

CoreAre compounds different from theelements in them? (continued)

Obtaining evidence (2)

6 Watch as some dilute sulphuric acid is added to one of the tubescontaining the mixture of iron and sulphur. A piece of papersoaked in lead nitrate solution is held near the mouth of the testtube. Lead nitrate is used as a test for the toxic gas hydrogensulphide.

7 Next your teacher will break one of the combustion tubes andput some of the compound formed after heating into anothertest tube, and do the same test with the sulphuric acid and thefilter paper soaked in lead nitrate.

Considering the evidence (2)

8 Do the mixture of iron and sulphur and the compound formedduring heating react in the same way when dilute sulphuric acidis added?

Evaluating

9 Suggest a way of separating the mixture of iron and sulphurbefore heating.

10 Do you think that your method would work after heating?11 What happens when the tube is heated that suggests a reaction

is taking place?12 Write a word equation for the reaction taking place when iron

and sulphur are heated.13 Draw how you think the atoms of iron and sulphur are arranged

before and after the reaction. What changes? What stays thesame?



F1bTeacher

activity notesMelting and boiling points

Running the activityCore (Extension): This sheet is for those who have accepted the concept that different materials havedifferent melting and boiling points, but need reinforcement. The extension is for pupils who havemastered the concept that changes in state occur at different temperatures and would benefit from furtherreinforcement and challenge. Metals X and Y are for extension pupils only. Both Core and Extensionquestions use the chart on the Resource sheet. You will need to blank off metals X and Y and the tablewhen photocopying the Resource sheet for Core pupils.

Help: This sheet has a simpler chart and is for pupils who have yet to cope with the concept of changes instate occurring at different temperatures for different materials.

Expected outcomesCore: Pupils will extend the idea to all elements having a unique, single, fixed temperature at which theychange state.

Help: Pupils will identify that metallic elements melt and boil at different temperatures.

Extension: Pupils will also be able to link the use of known boiling point and melting point data toidentifying an unnamed substance if that substance melts or boils at one fixed temperature consistently.

AnswersCore (Extension):1 Potassium, mercury and zinc.

2 Aluminium, gold, tin, lead, iron, copper and silver.

3 iron

4 mercury

5 aluminium

6 potassium

7 Gold, iron and copper.

8 Potassium, mercury and zinc.

9 It would be the colour for solid from top to bottom

10 Tin and lead would both melt.

11 Each division is 10°C, so looks like 240°C.

12 Metal X is caesium, metal Y is nickel.

13 Only those with a melting point above 460°C, i.e. metal Y (nickel), aluminium, gold, iron, copper and silver.

Help:1 solid

2 gas

3 gas

4 solid

5 liquid

6 gas

7 titanium

8 Mercury is a gas at 400°C and tin is a liquid.


Type Purpose DifferentiationPaper Pupils use a resource sheet (core) to answer questions about the melting points and

boiling points of different metallic elements. Core (Extension), Help Resource


F1bActivity

CoreMelting and boiling points

All elements have their own unique different melting and boilingpoints. Use the Resource sheet to answer these questions aboutsome metallic elements.

1 Which metals melt and boil between −200ºC and 1600ºC?2 Which metals melt between −200ºC and 1600ºC, but do not

boil between these two temperatures?3 Which metal has the highest melting point?4 Which metal has the lowest melting point?5 Which metal has a melting point of 650ºC?6 Which metal has a boiling point of 760ºC?7 Which metals will be solids at 1000ºC?8 Which three metals would boil if you heated them to 1000ºC?9 Titanium has a melting point of 1660ºC. What would you see if

titanium was on the chart?10 Scientists are building a space probe to go to Venus.

Temperatures on Venus can be as high as 460ºC. The scientistsare not using any tin or lead in the space probe. Why not?


Extension

11 Lead has a melting point of 238ºC. Why is it difficult to show thisaccurately on the chart?

12 Identify metals X and Y using information on the Resource sheet.13 Scientists are building a space probe to go to Venus.

Temperatures on Venus can be as high as 460ºC. Which of themetals in the chart could be used to build the space probe?Explain why you chose these metals.


F1bActivity

HelpMelting and boiling points


All elements have their own special melting and boiling points.Use the diagram below to answer these questions about somemetallic elements.

1 Find water on the chart.

1 Is water a solid, a liquid or a gas at −100ºC?2 Is water a solid, a liquid or a gas at 200ºC?3 Is water a solid, a liquid or a gas at 400ºC?

2 Find mercury on the chart.

4 Is mercury a solid, a liquid or a gas at −100ºC?(Put a ruler along −100ºC.)

5 Is mercury a solid, a liquid or a gas at 200ºC?(Put a ruler along 200ºC.)

6 Is mercury a solid, a liquid or a gas at 400ºC?(Put a ruler along 400ºC.)

3 Scientists are building a space probe to land onVenus. On Venus the temperature is 460ºC. Thespace probe is made of metal.

7 Which metal would you use, titanium, tin ormercury?

8 Why did you choose this metal and not the others?

– 200

– 100

0

100

200

300

400

500

600

Tem

per

atu

re (

in º

C)

wat

erw

ater

tita

niu

mti

tan

ium

mer

mer

cur

cury

tin

wat

er

tita

niu

m

mer

cury

tin

gas liquid solid


F1bActivity ResourceMelting and boiling points


Use this table to help you answer Extension question 12.

Name of metal Melting point (°C) Boiling point (°C)

caesium 29 669

chromium 1857 2670

lithium 181 1342

magnesium 649 1107

nickel 1455 2725

titanium 1660 3231

– 200

gas

– 100

0

100

200

300

400

500

600

700

800

900

1000

1100

1200

1300

1400

1500

1600

liquid solid

Tem

per

atu

re (

in º

C)

po

tass

ium

alu

min

ium

alu

min

ium

go

ld

mer

mer

cury

tin

lead

iro

n

cop

per

zin

c

silv

er

met

al x

met

al x

met

al y

met

al y

po

tass

ium

alu

min

ium

go

ld

mer

cury

tin

lead

iro

n

cop

per

zin

c

silv

er

met

al x

met

al y


F2aTeacher

activity notesCollecting evidence for chemicalreactions

Running the activityPupils need to carry out the tests very carefully so that they do not miss any observations. The activity isintended to develop pupils’ observational skills and use these observations to justify why a chemicalreaction is said to have taken place.

You may wish to ask pupils to initially work alone and then share their observations with another pupil.Weaker pupils would benefit from working in pairs and may need support in vocabulary to use to recordtheir observations.

Core (Extension): Pupils carry out four reactions. As an extension pupils carry out the heating of sucrosewhich, if done gently as instructed, may only indicate physical change by melting. If it is heated further itwill show signs of chemical change in that it will change colour through yellow to brown and finally black.

Help: A table of results is provided for pupils to record their observations.

Expected outcomesCore (Extension): Pupils will carry out and record observations independently and identify precipitation,fizzing and colour change as characteristics of chemical change. They may also identify temperaturechange. From the extension activity pupils will also distinguish between physical change and chemicalchange.

Help: Pupils will identify precipitation, fizzing and colour change as characteristics of chemical change.

PitfallsIt is important to stress that the magnesium carbonate is reacting, not dissolving when hydrochloric acid isadded (link back to bubbles starter in F2 if used).

Safety notesEye protection must be worn. Suggested concentrations for hydrochloric acid and sodium hydroxide are0.4mol/dm3. The concentrations for silver nitrate and potassium iodide can be very low (0.05mol/dm3).The other solutions of sodium carbonate and copper(II) sulphate do not have to be of particularconcentrations. Ensure pupils only use small amounts of iron(II) chloride, magnesium carbonate andsucrose (sugar).

AnswersCore (Extension):

1 and 2 See sample results below.

Sample resultsSodium carbonate and iron(II) chloride: a dirty green precipitate is formed (basic iron(II) carbonate). Pupilsmay also see a few bubbles of carbon dioxide gas.

Magnesium carbonate and hydrochloric acid: the magnesium carbonate fizzes and a colourless gas is produced.A colourless solution (magnesium chloride) remains.

Copper(II) sulphate solution and sodium hydroxide solution: A pale blue precipitate is formed (copper(II)hydroxide).

Silver nitrate solution and potassium iodide solution: A yellow precipitate of silver iodide (AgI) is formed.

Heating sucrose: the sucrose melts and on further heating turns yellow, then brown and finally black.


Type Purpose DifferentiationPractical Pupils carry out a series of reactions to illustrate features associated with chemical

change.Core (Extension), Help


F2aTechnician

activity notesCollecting evidence for chemicalreactions

EquipmentFor each group:● six test tubes● test tube rack● spatula● solutions of sodium carbonate, dilute hydrochloric acid (0.4mol/dm3), silver nitrate solution, potassium

iodide solution and copper(II) sulphate● solids: iron(II) chloride, magnesium carbonate and sucrose (sugar)● Bunsen burner● heatproof mat● test tube holder

Notes on materials preparation:0.4mol/dm3 hydrochloric acid should be prepared in a fume cupboard by making up 35cm3 ofconcentrated hydrochloric acid to 1000cm3 with distilled water.

For your informationRunning the activityPupils need to carry out the tests very carefully so that they do not miss any observations. The activity isintended to develop pupils’ observational skills and use these observations to justify why a chemicalreaction is said to have taken place.

You may wish to ask pupils to initially work alone and then share their observations with another pupil.Weaker pupils would benefit from working in pairs and may need support in vocabulary to use to recordtheir observations.

Core (Extension): Pupils carry out four reactions. As an extension pupils carry out the heating of sucrosewhich, if done gently as instructed, may only indicate physical change by melting. If it is heated further itwill show signs of chemical change in that it will change colour through yellow to brown and finally black.

Help: A table of results is provided for pupils to record their observations.

Expected outcomesCore (Extension): Pupils will carry out and record observations independently and identify precipitation,fizzing and colour change as characteristics of chemical change. They may also identify temperaturechange. From the extension activity pupils will also distinguish between physical change and chemicalchange.

Help: Pupils will identify precipitation, fizzing and colour change as characteristics of chemical change.

PitfallsIt is important to stress that the magnesium carbonate is reacting, not dissolving when hydrochloric acid isadded (link back to bubbles starter in F2 if used).

Safety notesEye protection must be worn. Suggested concentrations for hydrochloric acid and sodium hydroxide are0.4mol/dm3. The concentrations for silver nitrate and potassium iodide can be very low (0.05mol/dm3).The other solutions of sodium carbonate and copper(II) sulphate do not have to be of particularconcentrations. Ensure pupils only use small amounts of iron(II) chloride, magnesium carbonate andsucrose (sugar).


Type Purpose DifferentiationPractical Pupils carry out a series of reactions to illustrate features associated with chemical

change. Core (Extension), Help


F2aActivity

CoreCollecting evidence for chemicalreactions

You are going to carry out three reactions and from your carefulobservations identify evidence to support the idea that compoundscan react together to form new substances.

Equipment● six test tubes ● Bunsen burner● test tube rack ● heatproof mat● spatula ● test tube holder● solutions of sodium carbonate, dilute hydrochloric acid, silver nitrate, potassium iodide,

copper(II) sulphate and sodium hydroxide● solids: iron(II) chloride, magnesium carbonate (and sucrose (sugar) for extension)

Obtaining evidence1 Draw a table to record your results. Your teacher may help you to do this.2 Make sure you observe and record all your observations carefully during the

experiments. Take care to mix solutions thoroughly.

A Chemical reaction between iron(II) chloride and sodium carbonate3 Add a small amount of iron(II) chloride to 3 cm depth of water in a test tube and

shake gently until the solid dissolves.4 Pour 3 cm depth of sodium carbonate solution into a second test tube.5 Slowly add the iron(II) chloride solution to the sodium carbonate solution.

B Chemical reaction between magnesium carbonate and hydrochloric acid6 Put a small amount of magnesium carbonate into a test tube and add 3 cm depth of

dilute hydrochloric acid.

C Chemical reaction between copper(II) sulphate solution and sodium hydroxide solution.7 Put 3 cm depth of copper(II) sulphate solution into a test tube and slowly add sodium

hydroxide solution.

D Chemical reaction between silver nitrate and potassium iodide8 Pour 3 cm depth of silver nitrate into a test tube and add potassium iodide solution.

Considering the evidence1 What evidence is there in each case that a chemical reaction has taken place?

Remember that in a chemical reaction, new materials are produced.

Heating sucrose

9 Put one spatula measure of sucrose into a dry test tube.10 Hold the test tube in a test tube holder and heat it gently with a Bunsen burner,

observing all the changes you see.2 What do your observations suggest is happening here?


Wear eyeprotection.

Avoid skincontact with these

chemicals. Wash yourhands afterwards.

Extension


F2aActivity

HelpCollecting evidence for chemicalreactions


Name and Name and What I observed Evidence for appearance of appearance of when chemical 1 chemical reaction chemical 1 before chemical 2 before was added to taking placereaction reaction chemical 2

iron(II) sodium chloride carbonate

magnesium hydrochloric carbonate acid

copper(II) sodium sulphate hydroxidesolution

silver potassium nitrate iodide solution solution


F2bTeacher

activity notesReacting ammonia with hydrogenchloride

Running the activityShow the class the tube and basic equipment set up before you transfer the tube to the fume cupboard toinsert the chemicals. If time permits get the class to help you place the pH paper along the tube – a glassrod is useful to help push the pH paper in place and a metre rule placed below the tube allows you to spacethe paper accurately every 10cm. You may find it useful to quickly recap colour changes for pH.

Depending on conditions it usually takes about 10–15 minutes for the characteristic white plume ofammonium chloride to appear. You will see the pH paper changing before this happens.

Core (Extension): A summary diagram of the apparatus is provided along with questions to prompt pupils torecord and interpret their observations. Further extension questions encourage pupils to discuss thereaction in terms of rate of particle movement and rearrangement of atoms.

Expected outcomesCore: Pupils will identify change in pH as another indicator of chemical change and will identifydifferences in pH, state and colour as indications that ammonium chloride is different from ammonia gasand hydrogen chloride gas.

Extension: Pupils will also use their ideas of particle movement and rearrangement to explain how theammonium chloride has been formed.

PitfallsSome pupils will become muddled between hydrogen chloride gas and hydrochloric acid. It may be worthdiscussing their chemical formulae and state. Take care that you use full strips of pH paper and that one isplaced about two thirds along the tube from the ammonia end otherwise you will not register pH 7 for theproduct. Make sure the outer parts of the rubber bungs stay dry, otherwise you will introduce fumes fromthe two reactants into the classroom. Use two retort stands placed carefully so as not to obstruct the pupils’view.

Safety notesThe demonstration must be set up in a fume cupboard and only when the tube is firmly sealed can it beplaced in front of the class for observation.

Concentrated hydrochloric acid and ammonia solution must be handled in the fume cupboard. Forceps areusually much easier to use than tweezers to soak the cotton wool and transfer it to the tube.

Ammonia can trigger asthma attacks in susceptible people so do carry out the activity in a well-ventilatedroom and return the tube to the fume cupboard as soon as it is convenient.

AnswersCore:1 Hydrochloric acid. 2 Ammonia gas. 3 Goes red (acidic). 4 Goes blue/black (alkali). 5 Whitefumes and then a white solid ring. 6 Changes from acidic to neutral to alkali (or reverse).7 colourless 8 white 9 solid 10 Has a pH of 7, is white in colour and is a solid. 11 It changes toneutral where the ammonium chloride is formed, which is different from the acidic hydrogen chloride andthe alkaline ammonia. 12 Appearance of a white solid.

Extension:13 Closest to the hydrochloric acid end (2/3 along the tube). 14 Ammonia molecules move faster thanhydrogen chloride molecules. 15 That the number of atoms it contains is one atom of nitrogen, fouratoms of hydrogen and one atom of chlorine.


Type Purpose DifferentiationPractical Demonstration to show pupils, through the reaction between ammonia and hydrogen

chloride, that pH can also indicate a chemical change.Core (Extension)


F2bTechnician

activity notesReacting ammonia with hydrogenchloride

EquipmentFor the teacher demonstration:

For your informationRunning the activityShow the class the tube and basic equipment set up before you transfer the tube to the fume cupboard toinsert the chemicals. If time permits get the class to help you place the pH paper along the tube – a glassrod is useful to help push the pH paper in place and a metre rule placed below the tube allows you to spacethe paper accurately every 10cm. You may find it useful to quickly recap colour changes for pH.

Depending on conditions it usually takes about 10–15 minutes for the characteristic white plume ofammonium chloride to appear. You will see the pH paper changing before this happens.

Core (Extension): A summary diagram of the apparatus is provided along with questions to prompt pupils torecord and interpret their observations. Further extension questions encourage pupils to discuss thereaction in terms of rate of particle movement and rearrangement of atoms.

Expected outcomesCore: Pupils will identify change in pH as another indicator of chemical change and will identifydifferences in pH, state and colour as indications that ammonium chloride is different from ammonia gasand hydrogen chloride gas.

Extension: Pupils will also use their ideas of particle movement and rearrangement to explain how theammonium chloride has been formed.

PitfallsSome pupils will become muddled between hydrogen chloride gas and hydrochloric acid. It may be worthdiscussing their chemical formula and state. Take care that you use full strips of pH paper and that one isplaced about two thirds along the tube from the ammonia end otherwise you will not register pH 7 for theproduct. Make sure the outer parts of the rubber bungs stay dry otherwise you will introduce fumes fromthe two reactants into the classroom. Use two retort stands placed carefully so as not to obstruct the pupils’view.

Safety notesThe demonstration must be set up in a fume cupboard and only when the tube is firmly sealed can it beplaced in front of the class to observe.

Concentrated hydrochloric acid and ammonia solution must be handled in the fume cupboard. Forceps areusually much easier to use than tweezers to soak the cotton wool and transfer it to the tube.

Ammonia can trigger asthma attacks in susceptible people so do carry out the activity in a well-ventilatedroom and return the tube to the fume cupboard as soon as it is convenient.


Type Purpose DifferentiationPractical Demonstration to show pupils, through the reaction between ammonia and hydrogen

chloride, that pH can also indicate a chemical change.Core (Extension)

● access to a fume cupboard● diffusion tube (preferably 1metre length)● concentrated ammonia solution● concentrated hydrochloric acid● forceps/tongs

● cotton wool● universal indicator paper● metre rule● two retort stands and clamps● eye protection


F2bActivity

CoreReacting ammonia with hydrogenchloride

Your teacher is going to demonstrate the chemical reaction betweenammonia gas and hydrogen chloride gas. Observe carefully to seewhat clues there are to tell us that a new substance has been formed.

Obtaining evidenceThe chemical reaction isgoing to take place insidea sealed glass tube.

To carry out the reactionyour teacher will place pH paper every 10cm along the length of the glass tube. Insert apiece of cotton wool soaked in ammonia solution at one end of the glass tube and sealthis end of the tube with a rubber bung. Quickly insert a second piece of cotton woolsoaked in hydrochloric acid into the other end of the tube and again use a rubber bungto seal the tube.

1 You will then carry out observations on the tube and its contents every few minutes.You can write a word equation to show the chemical reaction:ammonia ++ hydrogen chloride →→ ammonium chloride

Considering the evidence1 Which chemical releases fumes of hydrogen chloride gas?2 What does the ammonia solution release?3 What happens to the pH paper closest to the hydrochloric acid?4 What happens to the pH paper closest to the ammonia solution?5 What appears in the tube after a few minutes?6 What happens to the pH paper along the length of the tube?7 What colour is ammonia gas and hydrogen chloride gas?8 What colour is the ammonium chloride?9 Is the ammonium chloride a solid, a liquid or a gas?

Evaluating the results10 State three ways in which ammonium chloride is different from ammonia gas and

hydrogen chloride gas.11 What evidence does the pH paper provide that a chemical change has taken place?12 What further evidence do we have that the ammonia gas and hydrogen chloride gas

have reacted?

13 Where in the tube does the ammonium chloride appear?14 What does this tell you about the movement of the

molecules of hydrogen chloride gas compared to the movement of the ammonia gas?15 The formula for ammonium chloride is NH4Cl. What does this tell you about the

elements present?


Wear eyeprotection.

glass tube

cotton wool soakedin ammonia

pH papercotton wool soaked in hydrochloric acid

rubberbung

rubberbung

Extension


F3aTeacher

activity notesA closer look at salty water

Running the activityThe purpose of this activity is to illustrate how impurities affect the freezing pointof a pure substance, in this case water. Lots of crushed ice is needed for thisactivity. Pupils should be shown how to remove a thermometer from ice byallowing the ice to melt before trying to remove it.

Pupils could also work in pairs with one pupil collecting the temperature readingsfor the pure water sample and the other collecting the temperature readings forthe salt solution. The activity could be carried out using datalogging equipment.You could also vary the amount of salt dissolved in the salt solution samples givenout to pupils and look at the variation in data collected.

Weaker pupils will need support in presenting their data as a line graph.

Other relevant materialSkill sheet 5: Drawing charts and graphsSkill sheet 6: Interpreting graphs

Expected outcomesPupils will collect and present data. They will identify that salt lowers the freezingpoint of water. The extension question encourages pupils to use their ideas ofparticles to suggest how the salt might prevent the water from freezing at 0°C.

AnswersCore:1 The temperature of the pure water will lower until 0°C and then stop. Pupil

responses will vary for the salty water.

2 Various possibilities will arise. Typical results should produce the following:

3 0°C

4 Freezes/becomes solid.

5 Will vary, typical results −2°C to −5°C.

6 The salt water may well still be a liquid at minus values.

7 The salt reduces the freezing point.

Extension:8 Typical responses will include some reference to the salt blocking the water

molecules. We are not looking necessarily for accurate science here but ratheran effort to apply their ideas and understanding of how particles may behave.


Type Purpose DifferentiationPractical Pupils compare the freezing point of a sample of pure water and a sample of water

which contains dissolved salt.Core (Extension)

Tem

per

atur

e (°

C)

Time

0

20

Tem

per

atur

e (°

C)

Time

liquid A liquid B

0

20


F3aTechnician

activity notesA closer look at salty water

EquipmentFor each pupil:● 250cm3 beaker● two boiling tubes● thermometer (−10 to 110°C)● ice cubes (to be crushed)● salt● glass rod● tablespoon● pure water labelled A● salt solution labelled BNB: Short stirring thermometers are ideal for this activity.

For your informationRunning the activityThe purpose of this activity is to illustrate how impurities affect the freezing pointof a pure substance, in this case water. Lots of crushed ice is needed for thisactivity. Pupils should be shown how to remove a thermometer from ice byallowing the ice to melt before trying to remove it.

Pupils could also work in pairs with one pupil collecting the temperature readingsfor the pure water sample and the other collecting the temperature readings forthe salt solution. The activity could be carried out using datalogging equipment.You could also vary the amount of salt dissolved in the salt solution samples givenout to pupils and look at the variation in data collected.

Weaker pupils will need support in presenting their data as a line graph.

Other relevant materialSkill sheet 5: Drawing charts and graphsSkill sheet 6: Interpreting graphs

Expected outcomesPupils will collect and present data. They will identify that salt lowers the freezingpoint of water. In the extension question pupils are also encouraged to use theirideas of particles to suggest how the salt might prevent the water from freezingat 0°C.


Type Purpose DifferentiationPractical Pupils compare what happens to the freezing point of a sample of pure water and a

sample of water which contains dissolved salt when they cool them both down.Core (Extension)


F3aActivity

CoreA closer look at salty water

In this investigation you are going to compare what happens tothe freezing point of a sample of pure water with a sample ofwater which contains dissolved salt. When salt dissolves in water itproduces a salt solution. A salt solution is an example of a mixture.

Equipment

● beaker ● glass rod● two boiling tubes ● tablespoon● thermometer ● pure water (sample A)● ice cubes (to be crushed) ● salt solution (sample B)● salt

Planning and predicting

Before you carry out this activity:

1 Write down what you predict will happen to the temperature ofthe pure water and the salty water as you cool each of themdown.

2 Sketch the shape of a graph you think your results will producefor the pure water and the salty water.

Obtaining evidence

1 Draw a table like the one below to record your results.


Time (s) Temperature of A (°C) Temperature of B (°C)

2 Decide what time intervals you will use.3 Half fill the beaker with crushed ice and add two tablespoonfuls

of salt. Stir the mixture with the glass rod. This mixture will lowerthe temperature down to about −5 °C. Measure the temperatureto check this. You will use this mixture to cool liquids A and B.

4 Put 5 cm depth of liquid A into a boiling tube and put thethermometer into the liquid. Leave the thermometer there untilthe end of the experiment.

5 Place the tube in the beaker of ice and salt to cool it.6 Take the temperature of the liquid at regular intervals until the

temperature is constant.7 Repeat the experiment with 5 cm depth of liquid B.

ice andsalt


F3aActivity

CoreA closer look at salty water (continued)

Presenting the results

8 Plot graphs of your results, using axes like these. Draw the bestcurve through the points each time.

Considering the evidence

3 What is the lowest temperature reached by the purewater?

4 What happens to the water at this temperature?5 What is the lowest temperature reached by the salt

water?6 Is the salt water a solid or a liquid at this temperature?

Evaluating

7 What effect does the salt appear to have on the cooling of thewater?


Time (s)

Tem

per

atur

e (°

C)

Extension

8 How might the salt molecules prevent the water molecules fromfreezing?


F3bTeacher

activity notesThe effect of salt on the boilingpoint of water

Running the activityThe purpose of this activity is to link impurities to changes in the boiling pointdata for water. You could again vary the amount of salt dissolved in the saltsolution samples given out to pupils and look at the variation in data collected.Instructions are provided for the activity.

Expected outcomesCore (Extension): Pupils will identify that salt raises the boiling point of water. Inthe extension, pupils are also encouraged to generalise their ideas about the effectsof impurities on the boiling point and freezing point of water.

Safety notesEye protection is required. If the salt solutions are strongly heated they tend to spithot salt, especially when nearly boiled dry.

AnswersCore:1 Pupils may well opt to suggest that the boiling point will be lower based on

what they have just experienced with freezing salty water.

2 100°C

3 Higher

4 Responses will vary.

5 The salt is raising the temperature.

Extension:6 Any sensible response which suggests a similar effect to the salt, i.e. freezing

point lowered, boiling point raised.


Type Purpose DifferentiationPractical Pupils compare the boiling point of a sample of pure water and a sample of water which

contains dissolved salt.Core (Extension)


F3bTechnician

activity notesThe effect of salt on the boilingpoint of water

EquipmentFor each group:● boiling tube● thermometer (−10 to 110°C)● clamp● Bunsen burner● heatproof mat● pure water labelled A● salt solution labelled BNotes on materials preparation:A long thermometer is better than a short stirring thermometer for this activity.

For your informationRunning the activityThe purpose of this activity is to link impurities to changes in the boiling pointdata for water. You could again vary the amount of salt dissolved in the saltsolution samples given out to pupils and look at the variation in data collected.Instructions are provided for the activity.

Expected outcomesCore (Extension): Pupils will identify that salt raises the boiling point of water. Inthe extension, pupils are also encouraged to generalise their ideas about the effectsof impurities on the boiling point and freezing point of water.

Safety notesEye protection is required. If the salt solutions are strongly heated they tend to spithot salt, especially when nearly boiled dry.


Type Purpose DifferentiationPractical Pupils compare the boiling point of a sample of pure water and a sample of water which

contains dissolved salt.Core (Extension)


F3bActivity

CoreThe effect of salt on the boilingpoint of water

We have already seen that impurities such as salt can affect thefreezing point of water. In this activity we will be looking to see ifimpurities such as salt can also affect the boiling point of water.Remember when salt dissolves in water it produces a salt solution.A salt solution is an example of a mixture.

Equipment● boiling tube ● Bunsen burner ● pure water (liquid A)● thermometer ● heatproof mat ● salt solution (liquid B)● clamps

Planning and predictingBefore you carry out this activity:

1 Write down what you predict will happen to the temperature of the pure water andthe salty water as you heat each of them.

Obtaining evidence1 Put about 5 cm depth of liquid A (pure water) into the

boiling tube and clamp the tube at an angle as shown.2 Adjust the Bunsen burner to give a small flame.3 Start heating the boiling tube.4 Clamp the thermometer so that the bulb of the thermometer

is in the liquid, as shown in the diagram.5 When the liquid boils, record the highest temperature shown.6 Repeat the experiment with liquid B.

Considering the evidence2 What was the boiling point of the pure water (liquid A)?3 Was the boiling point of the salt solution (liquid B) the same,

higher than or lower than that of the pure water?4 How does this temperature value compare to your prediction in question 1?

Evaluating5 What appears to be the effect of salt on the boiling point of water?


Wear eyeprotection.

heat

6 What would happen to the freezing point and boiling pointof water if we substituted sugar for the salt?

Extension


F4aTeacher

activity notesWhat’s in the air?

Running the activityQuickly carry out the demonstration first. This means that you can then discussand comment on pupils’ observations while the apparatus cools down, which cantake up to 20 minutes. Use the samples of copper oxide and copper powder to helppupils compare what is happening inside the apparatus. You can substitute copperturnings or copper wire for the copper powder. Weaker pupils will need support tocarry out the calculations and present the results as a percentage. Encourage pupilsto use drawings to suggest what they think is happening. Mini whiteboards areuseful here. You may find it helpful to use molymod or an alternative to model in3D what is happening at the molecular level.


Expected outcomesPupils will identify evidence that air is a mixture which includes oxygen andcalculate the percentage of oxygen present in the sample of air used. Pupils willrepresent the reaction using drawings. Some pupils will also recognise that thepercentage of oxygen in air can vary.

PitfallsYou will obtain erroneous results if you do not allow the remaining air left in thesystem to cool before you take volume readings.

Safety notesAvoid raising dust from the copper powder as it is a respiratory irritant.

AnswersCore:1 Responses will vary.

2 Some pupils may link back to previous units where the composition of air hasbeen touched on and the presence of oxygen in air has been discussed.

3 Gone from pink to black.

4 Results should give a value between 78 and 80cm3.

5 oxygen

6 copper + oxygen → copper oxide

7 No more oxygen left to react with.

8 Colour change, drop in volume of air.

9 Unused copper and yet still an amount of air left in the syringes.

10 Cannot push both syringes to zero.

Extension:11 Similar results.

12 Responses will vary but you are looking for pupils to offer reasons why theremay be more or less oxygen present in a given air sample.


Type Purpose DifferentiationPractical Demonstration to show pupils that air contains oxygen but must also contain

other gases.Core


F4aTechnician

activity notesWhat’s in the air?

EquipmentFor the teacher demonstration:● copper powder● hard glass tube● two ground glass syringes● Bunsen burner● sample of copper oxide in sealed container, labelled● sample of copper powder in sealed container, labelled

For your informationRunning the activityQuickly carry out the demonstration first. This means that you can then discussand comment on pupils’ observations while the apparatus cools down, which cantake up to 20 minutes. Use the samples of copper oxide and copper powder to helppupils compare what is happening inside the apparatus. You can substitute copperturnings or copper wire for the copper powder. Weaker pupils will need support tocarry out the calculations and present the results as a percentage. Encourage pupilsto use drawings to suggest what they think is happening. Mini whiteboards areuseful here. You may find it helpful to use molymod or an alternative to model in3D what is happening at the molecular level.


Expected outcomesPupils will identify evidence that air is a mixture which includes oxygen andcalculate the percentage of oxygen present in the sample of air used. Pupils willrepresent the reaction using drawings. Some pupils will also recognise that thepercentage of oxygen in air can vary.

PitfallsYou will obtain erroneous results if you do not allow the remaining air left in thesystem to cool before you take volume readings.

Safety notesAvoid raising dust from the copper powder as it is a respiratory irritant.


Type Purpose DifferentiationPractical Demonstration to show pupils that air contains oxygen but must also contain other

gases.Core (Extension)


F4aActivity

CoreWhat’s in the air?

Your teacher is going to provide you with some evidence that showsair contains more than just oxygen. Observe carefully as you seecopper heated in a fixed amount of air. We know from previous activities that when copper is heated in air it will go black to form copper oxide.

To carry out the activity your teacher will place some copper powder in the hard glasstube. Then set the volume of air trapped inside syringe 1 at 0cm3 and the volume ofair trapped inside syringe 2 at 100cm3. They will then begin heating the copper andgently pass the air trapped inside the syringes backwards and forwards over thecopper powder. They will leave the apparatus to cool before reading the volumes ofair in each syringe.

Predicting

1 What do you think will happen to the amount of air trapped inside the syringes asthe copper is heated?

2 What evidence do you have to suggest this?

Obtaining evidence

3 How has the appearance of the copper changed?4 How much air is left inside the syringes?

Considering the evidence

5 What do you think has reacted with the copper?6 Write a word equation for the reaction.7 There’s still plenty of air in the syringes so why has some of the copper powder

not reacted?

Evaluating

8 What evidence do we have that a chemical reaction has taken place?9 What evidence do we have that there is no more oxygen for the copper to react

with?10 What evidence do we have that there is still air left inside the syringes?

11 What would you expect to happen if we repeated theexperiment using iron instead of copper?

12 Why might the amount of oxygen in our samples of air vary?


Wear eyeprotection.

heat

copper powder in hard-glass tube

syringe 1 syringe 2

Extension


F5aTeacher

activity notesWhat’s the ratio?

Running the activityThe examples used are ionic compounds. Some pupils may appreciate the ideathat the variation in the size of the cards used to model the chemical formulae isbased on the fact that we now know that each element has a ‘combining power’which determines the basic ratio needed for them to combine together.

The cards should be prepared using Resource sheet 1. These sheets can be enlargedto make the cards larger. With high-attaining groups, more cards can beintroduced. Suitable examples are provided on Resource sheet 2. These cardsintroduce pupils to the use of brackets in chemical formulae. You will also need todiscuss the idea that some combinations go around in ‘gangs’. Examples offormulae that pupils can be asked to work out using the cards from Resource sheet2 are: calcium carbonate (CaCO3), calcium sulphate (CaSO4), calcium hydroxide(Ca(OH)2), sodium sulphate (Na2SO4), sodium carbonate (Na2CO3), sodiumhydroxide (NaOH), aluminium hydroxide (Al(OH)3), aluminium nitrate(Al(NO3)3), aluminium carbonate (Al2(CO3)3), aluminium sulphate (Al2(SO4)3).

Other relevant materialSkill sheet 31: Writing formulaeResource 1 and 2

Expected outcomesPupils work out the chemical formulae for simple compounds.

Answers1 NaI

2 CaI2

3 MgO

4 MgCl25 Al2O3

6 AlN

7 Mg3N2


Type Purpose DifferentiationPaper Pupils deduce chemical formulae for simple compounds and identify the basic ratio of

the constituent elements.CoreResource 1Resource 2


F5aActivity

CoreWhat’s the ratio?

In this activity you are going to find the connection between the chemical formulaof a compound and the ratio of the atoms in it.

Equipmentcards labelled sodium, calcium, magnesium, aluminium, chloride, iodide, oxide and nitride

Obtaining evidence1 You are going to work out the chemical

formula for sodium chloride.

Find the sodium and chloride cards and putthem side by side. You have now made arectangle. The chemical formula for sodiumchloride is NaCl. This means that for every sodium atom there is a chlorine atom, sothe ratio of sodium atoms to chlorine atoms has to be:

sodium : chlorine1 : 1

This ratio is fixed. You cannot alter it without producing a different substance fromthe sodium chloride.

2 You are now going to work out the formula for calcium chloride.

When you put one calcium card beside one chloride card this time, you do not get arectangle. You can, however, get a rectangle if you use two chlorides. The chemicalformula for calcium chloride is CaCl2. This means that for every calcium atom thereare two chlorine atoms, so the ratio of calcium atoms to chlorine atoms has to be:

calcium : chlorine1 : 2

Again, this ratio is fixed. You cannot alter it without producing a different substancefrom the calcium chloride.

Now use the cards to work out the formulae for the following compounds.

1 sodium iodide 5 aluminium oxide2 calcium iodide 6 aluminium nitride3 magnesium oxide 7 magnesium nitride4 magnesium chloride

Remember, you must make a rectangle before you can write a formula. Draw a table likethe one below to record your work.



Nasodium

Nasodium

Clchloride

Clchloride

Name of compound Chemical formula Ratio of elements

Sodium chloride NaCl sodium : chlorine 1 : 1

Calcium chloride CaCl2 calcium : chlorine 1 : 2


F5aActivity

Resource 1What’s the ratio?


Ooxide

Ooxide

Ooxide

Ooxide

Cacalcium

Cacalcium

Cacalcium

Mgmagnesium

Alaluminium

Alaluminium

Alaluminium

Alaluminium

Nnitride

Nnitride

Mgmagnesium

Mgmagnesium

Ooxide

Ooxide

Nasodium

Clchloride

Clchloride

Clchloride

Clchloride

Clchloride

Clchloride

Clchloride

Iiodide

Iiodide

Iiodide

Clchloride

Nasodium

Nasodium

Nasodium


F5aActivity

Resource 2What’s the ratio?


Cacalcium

Cacalcium

Cacalcium

Cacalcium

SO4

sulphateSO4

sulphate

CO3

carbonate

CO3

carbonateCO3

carbonateCO3

carbonateCO3

carbonate

SO4

sulphateSO4

sulphateSO4

sulphate

Alaluminium

Alaluminium

Alaluminium

Alaluminium

Alaluminium

Alaluminium

Nasodium

Nasodium

Nasodium

Nasodium

Nasodium

Nasodium

NO3

nitrateNO3

nitrateNO3

nitrateNO3

nitrate

OHhydroxide

OHhydroxide

OHhydroxide

OHhydroxide

OHhydroxide

OHhydroxide

OHhydroxide

NO3

nitrateNO3

nitrate


F5bTeacher

activity notesFinding the composition ofmagnesium oxide

Running the activityThis activity is intended for higher attainers only. It is suggested that pupils work in pairs. The pupils needto practise manipulating the lid with the tongs so that they can lift it only partially to allow sufficient airto get to the magnesium but without losing any product! Make sure each group has at least 10cm ofmagnesium ribbon otherwise you risk ending up with data that you cannot work with.

The magnesium ribbon used either needs to be cut up into small pieces beforehand or wrapped looselyaround a small spatula to coil it up to fit into the crucible. Mass readings should be taken to two decimalplaces. As a guide, 20cm of magnesium weighs approximately 0.3g and should gain around 0.2g.

Expected outcomesFrom data collected pupils identify that a fixed relationship exists between magnesium and oxygen presentin any given sample of magnesium oxide, and confirm the formula as MgO.

PitfallsIf you use crucibles with badly fitting lids, expect more variation in the data collected. Unless you usebetween 10 and 20cm of magnesium ribbon the mass gains will not be significant. Avoid using oldmagnesium ribbon which will be dull in appearance due to oxide already formed. There is a risk of losingsome magnesium oxide if the lid is raised too high.

Safety notesMagnesium is highly flammable. Eye protection must be worn. Ensure pupils use all the magnesium theyare allocated. Beware of theft; keep stock secure. It is advisable that the magnesium ribbon is cut upbeforehand, if you are using pieces, and not by the pupils themselves.

ICT opportunitiesIt would be possible to set up a spreadsheet for the results and subsequent calculations.

Answers1 May not be sufficient oxygen in the air trapped inside the crucible for all the magnesium to react.

2 Allows further amounts of air to react with the magnesium.

3 Magnesium would react too quickly and violently, the magnesium oxide could easily escape andintroduce error into the results.

4 Answers will vary and may depend on the skill of the pupil in carrying out the activity but generallyexpect comments relating to… ‘all our readings increased’ … ‘the amount of increase varies’.

5 similar

6 Answers will vary. Pupils use their own mass reading data for their magnesium sample to read off fromthe graph a suggested value for the amount of oxygen. Pupils should comment and compare this valuewith their obtained value.

7 For example, didn’t heat long enough, left lid off and lost some ash.

8 Same ratio of 1:1 but mass readings would be different because copper atoms have a bigger mass thanmagnesium.


Type Purpose DifferentiationPractical Pupils burn magnesium in air and use data collected to decide if a fixed relationship

exists between the amount of magnesium and oxygen present in any given sample ofmagnesium oxide.

Extension


F5bTechnician

activity notesFinding the composition ofmagnesium oxide

EquipmentFor each group:● crucible and well-fitting lid● magnesium ribbon (between 10 and 20cm)● tongs● Bunsen burner● access to top pan balance (to two decimal places)● pipe-clay triangle● scissors

For your informationRunning the activityThis activity is intended for higher attainers only. It is suggested that pupils workin pairs. The pupils need to practise manipulating the lid with the tongs so thatthey can lift it only partially to allow sufficient air to get to the magnesium butwithout losing any product! Make sure each group has at least 10cm ofmagnesium ribbon otherwise you risk ending up with data that you cannotwork with.

The magnesium ribbon used either needs to be cut up in small pieces beforehandor it is wrapped loosely around a small spatula to coil it up to fit into the crucible.Mass readings should be taken to 2 decimal places. As a guide, 20cm ofmagnesium weighs approximately 0.3g and should gain around 0.2g.

Expected outcomesFrom data collected pupils identify that a fixed relationship exists betweenmagnesium and oxygen present in any given sample of magnesium oxide, andconfirm the formula as MgO.

PitfallsIf you use crucibles with badly fitting lids, expect more variation in the datacollected. Unless you use between 10 and 20cm of magnesium ribbon the massgains will not be significant. Avoid using old magnesium ribbon which will be dullin appearance due to oxide already formed. There is a risk of losing somemagnesium oxide if the lid is raised too high.

Safety notesMagnesium is highly flammable. Eye protection must be worn. Ensure pupils useall the magnesium they are allocated. Beware of theft; keep stock secure. It isadvisable that the magnesium ribbon is cut up beforehand, if you are using pieces,and not by the pupils themselves.

ICT opportunitiesIt would be possible to set up a spreadsheet for the results and subsequentcalculations.


Type Purpose DifferentiationPractical Pupils burn magnesium in air and use data collected to decide if a fixed relationship

exists between the amount of magnesium and oxygen present in any given sample ofmagnesium oxide.

Extension


F5bActivity

ExtensionFinding the composition ofmagnesium oxide

You know that magnesium burns in air to form magnesiumoxide. In this activity you will collect and use data to find outhow much magnesium and oxygen are present in themagnesium oxide that is formed.

Equipment

● crucible and well fitting lid ● access to top pan balance● magnesium ribbon (to two decimal places)● tongs ● pipe-clay triangle● Bunsen burner ● scissors

Obtaining evidence

1 You will need to record and use the following datareadings during the activity.


Wear eyeprotection.

Take care!Magnesiumis highly

flammable.

Wash your handsafterwards.

Mass of magnesium Mass of magnesium Mass of oxygen (g) oxide (g) (g)

2 Weigh the crucible + lid.3 Weigh the crucible + lid + magnesium.4 Find the mass of magnesium by subtracting the mass of the crucible + lid (step 2)

from the mass of magnesium, crucible + lid (step 3). Record this in your results table.5 Put the crucible, lid and contents on the pipe-clay triangle, making sure the lid is

secure. Practise lifting the lid on and off with the tongs.6 Make sure the lid is on the crucible and now begin heating the magnesium.7 After 5 minutes use the tongs to carefully tilt the lid a little so that you can expose the

burning magnesium to the air. Take care! If the magnesium flares up just replace thelid and continue heating and then try again. When no flaring is seen, leave thecrucible and contents to cool.

8 When cool, re-weigh the crucible, lid and contents.9 Find the mass of magnesium oxide by subtracting the reading you obtained for the

crucible + lid (step 2) from the final reading for the crucible + lid + contents (step 8).Record this in your results table.

10 Find out how much oxygen there is in your sample of magnesium oxide bysubtracting the mass of magnesium from the mass of magnesium oxide. Record thisin your results table.

cruciblewith lid

pipe clay triangle

magnesiumribbon

tripodheat


F5bActivity

ExtensionFinding the composition of magnesiumoxide (continued)

1 Why don’t we just heat the magnesium with the lid on all the time?2 Why does lifting the lid slightly during the activity help?3 What is wrong with just heating the magnesium in the crucible without a lid?


Remember, we now know from other scientists’ work that the atoms of magnesium andoxygen do not have the same mass. Magnesium atoms weigh more than oxygen atoms.In fact the ratio of mass of magnesium to mass of oxygen is 3:2.

You will need to keep this in mind when you look at the readings you have obtained.

Now use the data readings you have recorded to complete the grid below to work outwhat the ratio of magnesium to oxygen is in your sample of magnesium oxide.


Magnesium Oxygen

Enter the mass you have recorded in the activity. g g

We know the ratio of the mass of magnesium 3 2atoms to oxygen atoms is:

Work out the following to see if your data g/3 g/2reflects the same mass ratio.

Round up your mass ratio to the nearest wholenumber.

What number of atoms could this represent?

What does the data suggest for the formula of your magnesium oxide sample?

Considering the evidence4 Compare your data with the data from other groups. What is the same?

What is different?5 How do your results compare with the data from Craig’s class in the textbook on

pages 64– 65?

Evaluating6 Use Craig’s graph on page 65 of the textbook to find out how much oxygen it says

should react with the amount of magnesium you started with. How does this valuecompare with your data?

7 Suggest one source of error for this activity.8 What would you expect if we used copper in the experiment rather than magnesium?



F1 PlenariesCompounds all around

Review learning● Pupils work in threes. Each pupil becomes either Na, Cl, or NaCl (salt).● They each take a turn to say what it is about themselves that makes them

different from the other two. For example ‘sodium is different from chlorineand sodium chloride because ...’

● Provide pupils with the following vocabulary to use: atom, metallic element,non-metallic element, solid, gas, melting point, crystals.

● Ask individual pupils to share their responses with the class. Ask other pupilswho also had the same brief to state what they said and summarise theevidence for each.

Sharing responses● Ask one pair to share their observations from Activity F1a with the class. Did

everyone make the same observations? What does this tell us?● Ask pupils to suggest which observation they think is the key piece of evidence

for a change having taken place. The iron sulphide is still slightly magnetic sothe reaction with sulphuric acid provides more valid/convincing evidence.

● Ask a pair to share their word equation. Look at how they have written theword equation for the reaction. Has anyone done it differently? When doesthe order matter, when doesn’t it matter?

● Ask pupils to suggest what happens to the atoms of iron and sulphur duringthe reaction and sketch their ideas on a mini-whiteboard. Display their ideas;draw out similarities and differences.

Group feedback● Ask individual pupils to describe how they worked out their responses to a

given question. Did anyone do it differently? How?● Ask pupils to describe what happens to the atoms/particles in the metals when

they reach melting point and boiling point. What changes? What stays the same?● Now ask individual pupils to suggest their reasons as to why tin or lead will not

be suitable to use for the space probe and what data they used to make theirdecisions. So what would be a suitable metal to use? Why? If the space probebrought back samples of metals, what would they do to identify the metals?

Word game● Pupils identify the ‘odd man out’ in each list of three items and justify their

answer. See answers on the right.● Items: S, Na, Fe; H2O2, H2O, H2SO4; nitrogen, oxygen, water; melting point,

boiling point, freezing point; N2, O2, He.

Looking ahead● Set the question for pupils to consider and suggest answers to.● Then ask them to share their responses with other pupils. Make it clear they

may not know the answer and need to suggest their ideas and predictions.● Pupils can summarise the suggestions and record them in their books, to

reconsider after further lessons.

ChallengeWhat’s the differencebetween meltingpoint and freezingpoint?Answers to word gamesulphur – as it is non-metallic; H2SO4 –made of threeelements; water – acompound; boilingpoint – because melt-ing point is same asfreezing point; He –because it exists assingle atoms of gas

QuestionWhat clues wouldyou look for todecide if you hadmade something newor different whenyou put two or morechemicals together?


Review learning

Pupils summarise evidence theyhave to show that salt (sodiumchloride) is different from theelements it contains.

Sharing responses

Pupils discuss interpreting observationsin Activity F1a in terms of what ishappening at particle/atom level andidentifying the word equation.

Group feedback

Pupils discusspatterns in datafrom Activity F1b.

Word game

Pupils play oddman out.

Looking ahead

What evidence/clues wouldyou accept/look for thatshow a chemical reactionhas taken place?

F-Plenaries.qxd 25-Nov-03 9:07 AM Page 1


F2 PlenariesReacting compounds

Review learning● Pupils brainstorm what information they would want to include in a

summary of what to look for to spot a chemical reaction. Pupils workindividually or in pairs to present their own summary.

Sharing responses● Ask pairs of pupils to summarise their observations for one reaction in

Activity F2a. Ask the class to agree/disagree or add their observations. Repeatfor the remaining reactions. Summarise the key pieces of evidence to supportthe idea of a change.

● Now summarise the starting materials for the reactions between iron(II)chloride and sodium carbonate and magnesium carbonate and hydrochloricacid in this activity. Ask the class to suggest what they could put on theproduct side of the word equation. Use the word equation for iron sulphideand for the lead iodide reaction to help.

● Compare responses. Challenge responses that have products which containelements missing from the original starting materials.

Group feedback● Pupils summarise the evidence for chemical change in the reaction in

Activity F2b.● Provide pupils with the chemical formulae for the reactants and products.

Discuss which and how many elements are present in each compound.● Ask pupils to sketch what they think is the arrangement of atoms in the starting

materials. What clues do they use from the chemical formula to help them?● Compare pupil responses and then show them the accepted arrangement for

NH3.

Word game● Present each pupil with a card on which is written only one reactant or one

product from the examples of the reactions given. Ask pupils to look aroundand find other pupils to team up with to present a word equation for one ofthe chemical reactions they have met in Activity F2a and F2b.

● Ask pupils to step forward or raise their cards if they are: a) an element, b) acompound, c) a reactant, d) a product. Ask pupils to state one fact about thesubstance on their card.

● The winners are those who first present a complete reaction with reactantson the left and products on the right.

● With lower attainers you could show the word equations for a few secondsbefore they begin.

● With higher attainers just write the chemical formulae on the cards.

Looking ahead● Set the question on the right for individuals to consider and suggest answers

to. Then ask them to share their responses with other pupils. Make it clear theymay not know the answer and need to suggest their ideas and predictions.

ChallengeHow do they think theatoms are arranged inthe productammonium chloride?What information dothey need?

➔ Pupil sheet

Answerssodium carbonate +iron (II) chloride →sodium chloride + iron(II) carbonate;ammonia + hydrogenchloride →ammonium chloride;zinc + copper oxide →zinc oxide + copper;sodium iodide + leadnitrate → sodiumnitrate + lead iodide

QuestionBrainstorm all thethings you associatewith the term ‘pure’.


Review learning

Pupils present a summaryof what to advise a fellowpupil to look for to spot achemical change/reaction.

Sharing responses

Pupils discuss observationsin Activity F2a. Extend tolooking at word equationsto represent changes.

Group feedback

Pupils discuss observations fromActivity F2b and evidence forchemical change. They suggestwhat is happening in terms ofparticles and their rearrangement.

Word game

Pupils piece togetherword equations torepresent chemicalreactions described.

Looking ahead

Pupils discuss the use of theterm pure in everydaycontexts. They suggest whatthey understand by the termpure using their science ideas.


F2 PlenariesReacting compounds

Word game


zinccopper sodium lead oxide nitrate iodide

sodium iron(II) sodium iron(II)carbonate chloride chloride carbonate

ammoniahydrogen sodium zinc chloride chloride oxide

sodium lead ammoniumiodide nitrate chloride

copper



F3 PlenariesWhat’s in it?

Review learning● Individually, pupils identify key phrases/ideas that a working

definition of ‘mixture’ must include.

● Pupils then work in pairs to formulate a written definition.

● Ask pairs to share their ideas. Select a definition for all pupils torecord in their books.

Sharing responses● Ask a pair to present their graphs from Activity F3a on the OHT and

ask the class how these compare to their results. Discuss differencesand identify any anomalies. What evidence do the graphs give us thatthe salt is having an effect? What does the salt make when it is addedto the water – a mixture or a compound?

● Ask pupils to summarise in a sentence the effect of the salt. Comparedifferent responses. Agree a class summary which states the variablesby name. What do they think might happen if the activity wasrepeated but the mixture was made using copper sulphate instead ofsalt? Is there a golden rule here? How could we decide?

Group feedback● Ask individual pupils/pairs to summarise their results from Activity

F3b. Ask the class if they agree/disagree. Is there anything to add tothese results? Is there a pattern? What is it? Will this pattern berepeated for other mixtures involving water? How could we find out?What if we had a mixture that did not include water?

Word game● Pupils select nine words from the list to write into their bingo grid.

● Read out definitions from the teacher sheet in any order. Pupilsmatch these to their chosen words. The game is over when a pupilcan strike out a line.

● The ‘winning’ pupil has to recall the definitions of the words as theyread each one in the winning line to the class.

Looking ahead● Set the questions for individual pupils to consider and suggest

answers to. Then ask them to share their responses with other pupils.Make it clear they may not know the answer and need to suggesttheir ideas and predictions.

● Pupils can summarise the suggestions and record them in their books,to reconsider after further lessons.

ChallengeAsk pupils to share their ideasabout how the salt ispreventing the water fromcooling. Can they think of anexample of when thisbehaviour of salt is used?(Hint: winter travel.)

ChallengeCan pupils use their resultsfrom this activity to suggestwhat happens when: a) youadd salt to food whencooking, b) you add olive oilto the boiling water beforeputting in the pasta to cook, c)you add salt to boiling waterbefore adding the rice to cook?

➔ Teacher sheet

➔ Pupil sheet

QuestionWhat is the boiling point ofair? Does anyone know? Howcould we find out?


Review learning

Pupils produce their owndefinition of mixture.

Sharing responses

Pupils discuss graphs obtained from Activity F3aand what evidence this provides to show thatimpurities affect the behaviour of a substance.

Group feedback

Pupils compare dataobtained in Activity F3b.

Word game

Pupils play bingo.

Looking ahead

What is the boilingpoint of air?


XX



Word game

Choose nine words from the list below and write them in the empty grid.

Cross out each word when you hear the teacher read out its definition.

Shout BINGO! when you have crossed out a line of three words on the card.

The line can be across, down or diagonally.

molecule sodium chloride bubbles water crystal

chemical formula chemical reaction mixture boiling point

precipitate glucose pure substance



Word gameTeacher sheetRead out definitions below in any order.

1 A group of two or more atoms that are chemically combined together. [molecule]

2 Chemical name for table salt. [sodium chloride]

3 Example of evidence to show a chemical reaction has taken place. [bubbles]

4 A two-element compound. [water]

5 Word used to describe regular repeating shapes found in rocks andother solids. [crystal]

6 Describes or lists the elements contained in a compound. [chemical formula]

7 This takes place when atoms or molecules are rearranged to formnew substances. [chemical reaction]

8 Describes a material which contains two or more substancesjumbled up together. [mixture]

9 Temperature at which a substance changes state from liquid to gas. [boiling point]

10 Describes the solid made when two liquids react. [precipitate]

11 A three-element compound. [glucose]

12 Describes any element or compound. [pure substance]




F4 PlenariesThe air around us

Review learning● Ask a pair of pupils to suggest their sequencing for the statements on the

pupil sheet. Other groups are asked to confirm if they agree or disagree.

● Ask pupils to identify any statement that they found difficult to placeand say why. Ask what reasoning they used to decide where to place it.

● Summarise points made on the board or OHT for pupils to record.

Sharing responses● Ask the class to think about the following: What was the purpose of

Activity F4a? What took place in the activity? What evidence did wecollect?

● Then ask individual pupils to: a) recap the purpose of the experiment;b) summarise what took place in the experiment; c) identify theevidence collected to suggest that air is a mixture; d) draw how theythink the copper atoms and oxygen molecules reacted.

Group feedback● Pupils work in pairs. Present each pair with one of the scenarios. Ask

them to suggest what might be different about a sample of air fromtheir scenario compared to the air we have used in our activities andhow might this affect the data collected if we used these samples of airin our activity.

● Ask pairs to share their ideas. In what ways does the air behave like theother mixtures we have come across so far?

Word game● Give each pupil a card containing a question and an answer. Ask one

pupil to stand up and read out just the question on their card, then sitdown. The pupil who has an appropriate answer to this questionstands up, reads out their answer, then asks the question on their cardand sits down, and so on.

● The game is complete when the pupil who started the game stands upfor a second time to read out the answer on their card. The loop iscomplete.

● If there are not enough question/answer cards for the whole class, youmay need to make extra copies. Some pupils will have the samequestion/answer card – the first one to stand up gets to read theiranswer and ask their question.

Looking back● Pupils revise and consolidate knowledge from the unit. They can use

the Unit map, Pupil checklist, or the Test yourself questions.

➔ Pupil sheet

Correct sequence6, 2, 5, 4, 1, 7, 3

Suggested scenariosair collected from: a volcanicregion; a field containinglots of cows; a baby’sincubator in a hospital; abuilding that has airconditioning; an aeroplaneat the beginning and at theend of a 4 hour flight

➔ Pupil sheet

➔ Unit map

➔ Pupil checklist

➔ Test yourself


Review learning

Pupils sequence stages inthe liquefaction of air.

Sharing responses

Pupils summarise evidencefrom Activity F4a.

Group feedback

Pupils suggest what theywould expect if they usedsamples of air from differentsources in the experiment.

Word game

Check progress by playing aloop game reinforcing keywords from the unit.

Looking back

Pupils revise andconsolidate knowledge fromthe unit.



Review learning

1 The gases boil off one by one as they reach their own uniqueboiling point.

2 Next carbon dioxide gas and water vapour are removed.3 Xenon is the last gas in the mixture to reach its own boiling

point.4 This liquid mixture is then slowly warmed up.5 Then the remaining air is cooled down to around −200°C to

form a liquid.6 First air from outside is pumped into the plant and any dirt

removed.7 Nitrogen is the first gas in the mixture to reach its own boiling

point.

Sheet 1 of 1

Sheet 1 of 1


PlenariesF4 The air around us

Review learning

1 The gases boil off one by one as they reach their own uniqueboiling point.

2 Next carbon dioxide gas and water vapour are removed.3 Xenon is the last gas in the mixture to reach its own boiling

point.4 This liquid mixture is then slowly warmed up.5 Then the remaining air is cooled down to around −200°C to

form a liquid.6 First air from outside is pumped into the plant and any dirt

removed.7 Nitrogen is the first gas in the mixture to reach its own boiling

point.




Word game


QWhat chemical ismixed with grit onmotorways to helpprevent ice forming?

Amolecule

QWhat is special about the temperature0°C?

Asodium chloride

QWhat is the more common name forhydrogen oxide?

AIt is the freezingpoint of purewater and is alsothe melting pointof pure ice.

QThe atoms of someelements andcompounds areorganised in theseregular repeatingstructures.

Awater

QWhat is used to list theelements combined ina compound?

Acrystal

QThis takes place whenatoms or molecules arerearranged to formnew substances.

Achemical formula

QWhich type ofsubstance does nothave a unique boilingpoint or melting point?

Aa chemicalreaction

QWhat singletemperature recordsthe change of statefrom liquid to gas for a pure element orcompound?

Amixture

QWhat term describesthe solid formed whentwo liquids reacttogether?

Aboiling point

QName one thing tolook for to indicate achemical reaction istaking place.

Aprecipitate


F4 PlenariesThe air around us (continued)

Word game


QHow do we describe asubstance thatcontains only oneelement or onecompound?

Aa colour change

QComplete this wordequation: carbondioxide + water →

Aa pure substance

QCopper oxide, ironsulphide and water areall examples of what?

Aglucose + oxygen(sugar)

QWhich chemicalcontains the sameelements as water?

Atwo-elementcompounds

QWhich gas in air has aboiling point of−196°C?

Ahydrogenperoxide

QHow much oxygendoes air generallycontain?

Anitrogen

QWhich separatingprocess is used toextract nitrogen fromthe air?

A21%

QComplete this wordequation: zinc +copper oxide →

Adistillation

QWhat happens whenyou cool a gas?

Acopper + zincoxide

QHow do we describe agroup of two or moreatoms joined together?

AThe gascondenses tomake a liquid.



XX

Group feedback● Ask individual pupils to suggest a formula for one of the

named compounds in Activity F5a. Ask the class to confirmor disagree with their suggestion.

● What patterns or rules can they see for how elements chooseto combine with each other?

● Now ask pupils to produce a particle picture for air. Whatsteps do they need to work through? What rules apply tothe various components they will need to include?

● Compare the drawings and discuss the fact that since air is amixture, can we be specific about how many carbon dioxidemolecules we must draw compared to how many oxygenmolecules we should draw?

Bridging to other topics● Pupils are asked to think about their work with microscopes

and scale drawings: How is this work linked to the idea ofratios?

● What about when we make solutions? What about when wemake a cordial drink?

● How might ratios be important to gardeners and farmerswhen they each buy the same fertiliser to use on theirgardens and fields?


Group feedback

Pupils suggest a formula for one of thenamed compounds they met in Activity F5a.

Bridging to other topics

The class discusses and recaps othercontexts in which fixed ratios are used.

F5 PlenariesFormulae – Think about


F1 SpecialsCompounds all around

1 Use these words to fill in the gaps.

a An is made up of one kind of atom only.

Each one has a .

b A is made up of two or more kinds of

atom joined together. Each one has a .

c A is a group of atoms joined together. The atoms can be the same kind of atom or a group ofdifferent atoms.

2 Look at these drawings of substances.

a Which drawings show elements?

b Which drawings show compounds?

c Which drawings show molecules?

d Which drawings show crystals?

3 Write true or false for each sentence.

a Compounds are very different fromthe elements that make them up.

b The melting point is the temperature at which a solid

melts.

c A pure substance has a known melting point.


moleculeformula element symbol compound

A B

E F

C D

F-Specials.qxd 29-Oct-03 6:14 PM Page 1

F2 SpecialsReacting compounds

1 Draw lines to match the words to their descriptions.

2 Look at this list of observations.

Colour in the observations that show a chemicalreaction has happened.


reactants

products

precipitate

chemicalreaction

The colour stayedthe same.

Bubbles were made.

The temperature of the mixture stayed

the same.

There was a brightflash of light.

The mixture glowedhot by itself.

The solid melted.Energy is given out.

The colour changed.

A solid made whentwo liquids react.

New substances are made.

The substances westart with.

The substances that are madein a chemical reaction.


F2 SpecialsReacting compounds (continued)

3 Look at this word equation.

a Name the reactants.

and

b Name the products.

and

c Name the elements.

and

d Name the compounds.

and

4 Look at this word equation.

a Name the reactant.

b Name the products.

and

c Name the element.

d Name the compounds.

and


zinc + copper oxide → zinc oxide + copper

hydrogen peroxide → water + oxygen


F3 SpecialsWhat’s in it?

1 Use these words to fill in the gaps. You may use words once, more than once or not at all.

a A substance contains only one element or one compound.

b A contains more than one substance.

c The substances in a can vary.

The substances in a particular are always

the same.

2 Look at these diagrams showing the particles in somedifferent substances.

a Which substances are elements? , and .

b Which substances are compounds? , and .

c Which substances are mixtures? and .

d Which substances are pure? , , , ,

and .


puremolecule mixturecompound crystal

A B

E H

D

F

C

G


F4 SpecialsThe air around us

1 Use these words to fill in the gaps in the diagramshowing the state changes for any substance.

2 Write true or false for each sentence.

a The melting point is the temperature at which a

pure substance boils and condenses.

b The boiling point is the temperature at which a

pure substance boils and condenses.

c Pure substances melt and freeze at different

temperatures.

d Mixtures melt, boil, condense or freeze over a

range of temperatures.

e Pure substances boil and condense at one

temperature.

f Air is a pure substance.


meltingboiling freezingcondensing

gassolid liquid


F4 SpecialsThe air around us (continued)

3 Look at this list of gases.

a Air is made up mainlyof two gases. Colourthem in.

b Which gas makes uparound 21% of the

air?

c Look at these piecharts showing whatair is made up of.

Which pie chart is

correct?

4 The boiling point of nitrogen is −196 °C. The boiling point of oxygen is −183 °C.

a Look at this thermometer. The boiling point of nitrogen is marked on it.

Mark the boiling point of oxygen on thethermometer in a similar way.

b Which gas has the lowest boiling point?

c Which gas will boil first when a mixture is

heated?


chlorine oxygen hydrogen nitrogen

other gases

oxygen

nitrogen

other gases

oxygen

nitrogen

A

other gasesoxygen

nitrogen

C

oxygenother gases

nitrogen

D

B

– 200 °C

– 190 °C

– 180 °C

– 170 °C

– 160 °C

– 150 °C

– 140 °C

nitrogen


F5 SpecialsFormulae

1 Sodium chloride is a compound. For each sodiumatom (Na) there is one chlorine atom (Cl).

Which of these formulae is correct for sodiumchloride? Draw a circle around it.

Na2Cl Na2Cl3 NaCl NaCl2

2 Sodium oxide has the formula Na2O. Tick the correctstatement.

There is 1 sodium atom (Na) for every 2 oxygen atoms (O).

There is 1 sodium atom (Na) for every 1 oxygen atom (O).

There are 2 sodium atoms (Na) for every 1 oxygen atom (O).

3 Look at the drawings of these molecules. Draw linesto match them to the correct formulae.


CH4

C O

H2OC HH

H

HHCl

OO

O

OHH

ClHH2O2

HH CO2


F Specials answersCompounds and mixtures

F1 Compounds all around1 a element, symbol

b compound, formulac molecule

2 a A, Cb B, D, E, Fc A, B, E, Fd C, D

3 a trueb truec true

F2 Reacting compounds1 reactants – The substances we start with.

products – The substances that are made in achemical reaction.precipitate – A solid made when two liquidsreact.Chemical reaction – New substances are made.

2 Coloured in – Bubbles were made. There was abright flash of light. The colour changed. Themixture glowed hot by itself. Energy is givenout.

3 a zinc, copper oxideb zinc oxide, copperc zinc, copperd copper oxide, zinc oxide

4 a Hydrogen peroxide.b water, oxygenc oxygend hydrogen peroxide, water

F3 What’s in it?1 a pure

b mixturec mixture, compound

2 a A, F, Hb D, E, Gc B, Cd A, D, E, F, G, H

F4 The air around us1 Left to right – melting, boiling; freezing,

condensation2 a false

b truec falsed truee truef false

3 a Coloured in – oxygen, nitrogenb oxygenc C

4 a b nitrogenc nitrogen

F5 Formulae1 NaCl2 There are two sodium atoms (Na) for every one

oxygen atom (O).3


–200 °C

–190 °C

–180 °C

–170 °C

–160 °C

–150 °C

–140 °C

nitrogen

oxygen

CH4

C O

H2O

C HH

H

H

HCl

OO

O

OHH

ClHH2O2

HH CO2

Spe Answers.qxd 25-Nov-03 9:03 AM Page 6

F1 HomeworkCompounds all around

HELP

1 The list below contains some elements and some compounds.

a Write them into a table like the one shown. The first has beendone for you.

b Which substances contain more than two atoms?

c Which one is an element made from molecules?

d Which ones contain both a metal and a non-metal?

e Which compounds contain only non-metals?

2 Copy and complete the following sentences:

a A molecule is ...

b A compound is ...

c A substance represented by a symbol must be an ...


Fe CO2SCuO

Al2O3N2NaNH

3

Substance Element or compound

Fe Element

F-Homework.qxd 29-Oct-03 5:54 PM Page 1

F1 HomeworkCompounds all around (continued)

CORE

3 Look carefully at the information in the table below.

a What does the hazard symbol for magnesium tell you?

b i Say whether magnesium oxide could be safe to use in a medicine.ii Explain how you know.

c i Describe one thing about magnesium and oxygen that is similar.ii Describe one way in which magnesium and oxygen are different.

d i Draw a diagram showing how the atoms might be arranged inmagnesium oxide.

ii Oxygen is a molecule made from two oxygen atoms. Draw a diagramshowing what a few oxygen molecules might look like.

EXTENSION

4 Look at diagrams A to E.

a Which diagram could represent copper chloride?

b Which diagram could represent a solid metal element?

c Which diagram represents an element made ofmolecules?

d i Which two diagrams represent the same element?ii Explain your choice.iii In what way are the two substances you chose

different?

e Which substance is an element but not a molecule?

f Which three diagrams represent a solid element, agaseous element and the compound that is made when they react together?


Substance Symbol or Melting point Appearance Hazard formula (°C) symbol

Magnesium Mg 650 Shiny greysolid

Oxygen O2 −219

Magnesium MgO 2852 White powderoxide

A B

C D

E


F2 HomeworkReacting compounds

HELP

1 Here are some word equations representing four reactions.

a Draw a table with two columns. Label the first column‘Reactants’ and the second column ‘Products’.Write all of the reactants, from the word equations, in the firstcolumn and all of the products in the second.

b In equation B, the copper hydroxide is a precipitate. Whatdoes this tell you about it?

c In equation D, hydrogen is a gas. What would you see if youmixed sodium with water?

d Write down a list of all the compounds shown in the fourword equations.

CORE

2 Write word equations for each of the following reactions.

a Magnesium metal reacting with iron oxide to form iron metaland magnesium oxide.

b Methane burning in oxygen to form carbon dioxide andwater.

c Zinc reacting with hydrochloric acid to form hydrogen andzinc chloride.

d The reaction in which a precipitate of nickel hydroxide andsome potassium sulphate are formed from a mixture of nickelsulphate and potassium hydroxide.

e Make a list of all the elements you have written in your wordequations.


A magnesium + oxygen → magnesium oxide

B sodium hydroxide + copper sulphate →copper hydroxide + sodium sulphate

C aluminium + silicon dioxide →aluminium oxide + silicon

D sodium + water → sodium hydroxide + hydrogen


F2 HomeworkReacting compounds (continued)

EXTENSION

3 Bianca does some experiments. She mixes ammonium vanadate solutionwith zinc metal. The colour of the solution slowly changes from yellow toblue. Bubbles of gas are seen coming from the metal during the reaction.Bianca adds more zinc and leaves the mixture for an hour. She sees thecolour of the solution change from blue to green and then from green toviolet. At the end of the reaction most of the zinc has ‘disappeared’.

a Give two observations that suggest a reaction has occurred.

b Suggest one other observation, that Bianca could have made, thatwould have given more evidence that a reaction had occurred.

c Each colour represents a different compound that contains vanadium.How many different vanadium compounds did Bianca observealtogether?

d Bianca thinks that the gas might be hydrogen. Write down how shecould test the gas to see if she was right. (Hint: you found out aboutthis gas test last year.)

4 The formula of glucose is C6H12O6. Glucose is one of the reactantsinvolved in respiration, when it reacts with oxygen (formula O2) in cells.Respiration forms carbon dioxide (formula CO2) and water (formulaH2O).

a How many atoms are there in one glucose molecule?

b i How many carbon atoms are there in one carbon dioxidemolecule?

ii How many carbon dioxide molecules can be formed from oneglucose molecule during respiration?

c i How many hydrogen atoms are there in one water molecule?ii How many water molecules can be formed from one glucose

molecule?

d i Which of the substances, described in the information at the startof the question, is not a compound?

ii Explain how you know this.

e i When respiration happens there are no bubbles of gas and nocolour change. What evidence would you look for to indicate thata reaction really is occurring?

ii Explain why this suggests that respiration is vital for the survival ofliving things.



F3 HomeworkWhat’s in it?

HELP

1 The diagram represents thesubstances found in the air.

a How does the diagram showthat air is a mixture?

b How many different substancesare shown in the diagram?

c How many of them are notmolecules?

d How many oxygen moleculesare shown?

e Name the three elementsshown.

f i How many different compounds are shown?ii Name them.

CORE

2 a The list below contains both mixtures and pure substances. Make atable with ‘Mixture’ and ‘Pure’ as headings. Then add each substancebelow to the correct column in your table.

b The sentences below describe how pure ethanol (alcohol) can beobtained from fermented sugar, by distilling the solution andcollecting the ethanol in it. The sentences are in the wrong order.Rewrite them in the correct order.

A Cool the condenser with tap water.

B Collect only the vapour that condenses at 78°C.

C Heat the fermented sugar solution in a flask.

D When the thermometer reads 100°C, stop collecting the ethanol.

E Pass the vapour into a condenser.


nitrogenatom

hydrogenatom

heliumatom

carbonatom

oxygenatom

zinc oxide cough medicine hair shampoo

salt (sodium chloride)

sea saltcarbon dioxide

exhaled air tap water distilled water


F3 HomeworkWhat’s in it? (continued)

EXTENSION

3 Sammy investigated some fruit juice. A panelon the carton had information about theingredients.

Sammy measured the pH of the fruit drink andfound that it was between pH 4 and pH 5. Shefiltered the fruit drink. She measured out100 cm3 of the filtrate and heated it until it wasdry. She was left with 165 mg of an orangeresidue in the evaporating basin. Next, Sammydistilled 100 cm3 of the fruit drink. She collected99.2 cm3 of a clear, colourless liquid that boiledat exactly 100 °C. Sammy sent the liquid to ananalytical laboratory that did some more testson it. They reported that it contained hydrogenand oxygen in the ratio 2:1. Sammy wonderedabout how she could find out if there really wasonly one type of food colouring in the juice.

a Which substance was responsible for the pH that Sammymeasured?

b What did Sammy remove when she filtered the juice?

c i Why did filtering the juice not remove the residueobtained after evaporation?

ii How much residue would Sammy have obtained if shehad heated 1 litre of juice?

d i What does the boiling point of the colourless liquidsuggest that it might be?

ii Explain how the information from the analytical laboratoryhelps to identify the colourless liquid.

e Describe how Sammy could find out if there was anotheryellow colouring in the juice. (Hint: this revises a processyou first met in Year 7.)

f i Which of the substances mentioned in the information isdefinitely pure?

ii Explain how you know this.

g Suggest a reason why water was put first in the list ofingredients.


Pure Fresh

With real orange bits

Ingredients :

water, reconstituted, orange juice,

sugar, reconstituted lemon juice,

citric acid, vitamin C, colourings

(Sunset yellow-E110),

flavourings.

Orangejuice


F4 HomeworkThe air around us

HELP

1 The table shows the composition of typical air from a country village,excluding water vapour.

a Draw a bar chart to display the percentages of the four mostcommon gases in the air. A mark will be given for goodpresentation quality.

b How would the bar chart be different if the air had come from aclassroom after an hour’s science lesson?

c i Which important compound has been missed out of the table?ii Why is it not possible to give a percentage for this compound?iii How would the amount of this compound be different in air

from over the ocean compared with air from over a desert?

CORE

2 a i Which of the substances named in the table contains morethan one type of atom?

ii If the formula of the substance is CO2, what is the ratio givenby its fixed composition?

b Ignoring the ‘Others’ in the table, how many peaks would beproduced if the air were put through a ‘gas chromatography’machine?

3 a A factory burns old tyres to generate heat for its kilns. The tyrescontain sulphur, which is added to harden the rubber. Suggest twosubstances that might also be in an air sample that was taken frominside the factory chimney.

b One of the polluting gases produced by the factory is soluble inwater. Suggest how the factory could prevent this gas from gettinginto the atmosphere.


Substance Typical percentage in air

Nitrogen 79

Oxygen 20

Helium 0.9

Carbon dioxide 0.04

Others Trace


F4 HomeworkThe air around us (continued)

EXTENSION

4 The table shows some data about the liquid components of atype of petrol mixture.

a i Draw a line graph of the number of carbon atoms (from5 to 9) in each molecule (x-axis) against the boiling point(y-axis).

ii What is the relationship between the number of carbonatoms in the molecule and the boiling point?

b This petrol mixture can be separated by distillation. Themixture is heated so that each component completely boilsout, in turn.i Which component would be distilled first?ii Explain why it would be first.

c i Sketch the shape of the cooling curve you would obtain,if a mixture of pentane, hexane and heptane vapourswere cooled from 100 °C to 20 °C.

ii Explain the reasons for the shape you have drawn.


Component Formula Boiling point (°C)

Pentane C5H12 36

Hexane C6H14 69

Heptane C7H16 98

Octane C8H18 126

Nonane C9H20 151


F1Homework

mark schemeCompounds all around


HELPQuestion Answer Mark

1 a Elements are: S, Na and N2Compounds are: CuO, CO2, NH3 and Al2O3 4Award 4 marks for all correct. Deduct 1 mark each misplaced substance, to max of 4.

b CuO, CO2, NH3, N2 and Al2O3 5

c N2 1

d CuO and Al2O3 2

e CO2 and NH3 2

2 a A molecule is a group of atoms joined together. 1Underscore shows material copied; the rest is the pupil response.

b A compound is a substance with more than one type of atom joined together. 1Underscore shows material copied; the rest is the pupil response.

c A substance represented by a symbol must be an element. 1Underscore shows material copied; the rest is the pupil response.

Total for Help 17

COREQuestion Answer Mark

3 a It is flammable. 1

b i It is safe. 1

ii It has no hazard warning symbol. 1

c i They are both elements. 1

ii Magnesium is a solid and oxygen is a gas. 1

d i Diagram shows: alternating magnesium and oxygen atoms 1of different sizes 1in a regular crystal lattice. 1

ii Diagram showing pairs of atoms, of equal size 1not joined to other pairs. 1

Total for Core 10

EXTENSIONQuestion Answer Mark

4 a A 1

b B 1

c C 1

d i B and D 1

ii Their atoms are the same size. 1

iii B is a solid and D is a liquid/they are in different states. 1

e E 1

f B, C and A 1

Total for Extension 8


F2Homework

mark schemeReacting compounds



1 a Reactants are: magnesium, oxygen, sodium hydroxide, copper sulphate, aluminium, silicon dioxide, sodium and water. 5Products are: magnesium oxide, copper hydroxide, sodium sulphate, aluminium oxide, silicon, sodium hydroxide and hydrogen.All correct = 5 marks. Deduct 1 mark for each error to a maximum of 5.

b It is insoluble in water. 1

c Bubbles. 1

d Magnesium oxide, sodium hydroxide, copper sulphate, copper hydroxide, 5sodium sulphate, silicon dioxide and aluminium oxide.All correct = 5 marks. Deduct 1 mark for each error to a maximum of 5.

Total for Help 12


2 a Magnesium + iron oxide → iron + magnesium oxide 21 mark for reactants and 1 mark for products.

b Methane + oxygen → carbon dioxide + water 21 mark for reactants and 1 mark for products.

c zinc + hydrochloric acid → zinc chloride + hydrogen 21 mark for reactants and 1 mark for products.

d nickel sulphate + potassium hydroxide → nickel hydroxide + 2potassium sulphate 1 mark for reactants and 1 mark for products.

e Elements are: magnesium, iron, oxygen, zinc, hydrogen 5

Total for Core 13


3 a Change in colour; bubbling/gas given off. One mark for each correct answer. 2

b Temperature change. 1

c Four. 1

d Collect a test tube of the gas. Place a lighted splint at the mouth of the tube. Ifthe gas ignites with a pop, it is hydrogen. One mark for each correct answer. 3

4 a 24 1

b i 1 1

ii 6 1

c i 2 1

ii 6 1

d i Oxygen 1

ii It contains only one type of atom. 1

e i A temperature change. 1

ii It is the process that transfers chemical energy in glucose into the heat energyneeded to keep warm. Accept equiv answers referring to movement/growth etc. 1



F3Homework

mark schemeWhat’s in it?



1 a It contains different types of molecules. 1

b 5 1

c 1 1

d 6 1

e Oxygen, nitrogen and helium. 3

f i 2 1

ii Water and carbon dioxide. 2

Total for Help 10


2 a The mixtures are:cough medicine, hair shampoo, sea salt, exhaled air, tap water.The pure substances are:zinc oxide, salt (sodium chloride), carbon dioxide, distilled water. 5All correct = 5 marks. Deduct 1 mark for each misplaced item to a maximum of 5.

b C somewhere before E. 1E somewhere before A. 1A somewhere before B. 1B somewhere before D. 1

Total for Core 9


3 a Citric acid or lemon juice. 1

b Bits of orange flesh. 1

c i It was soluble in the juice. 1

ii 1650mg 1

d i It might be water 1

ii It contains hydrogen and oxygen in the same ratio as water/it has the same 1fixed composition as water.

e Do chromatography 1by spotting the juice onto chromatography paper 1standing it in a solvent 1and allowing the solvent to spread up the paper. 1

f i The water 1after distillation 1

ii It had a fixed boiling point/it had a fixed composition. 1

g It is the main component of the juice. 1



F4Homework

mark schemeThe air around us



1 a Correct labels. 1Appropriate scales. 1Accurately drawn bars. 1High overall quality of presentation. 1

b It would contain less oxygen 1and more carbon dioxide. 1

c i Water. 1

ii Its amount varies. 1

iii Higher over the ocean than over the desert. 1

Total for Help 9


2 a i Carbon dioxide 1

ii Carbon:oxygen = 1:2 1

b 4 1

3 a Two from:soot, smoke particles, carbon, sulphur dioxide, water vapour. 2

b Pass the gases through water before releasing them into the atmosphere. 1

Total for Core 6


4 a i Axes correct way round (boiling point on the vertical). 1Axes labelled. 1Suitable scales. 1Accurately plotted points. 1Best fit line drawn (should be very slightly curved). 1

ii The greater the number of carbon atoms, the higher the boiling point. 1

b i Pentane. 1

ii It has the lowest boiling point/It would boil before the others. 1

c i Graph should have:time on the x-axis 1boiling point on the y-axis 1show a general temperature decrease with increase in time 1have plateaux at 36 °C, 69 °C and 98 °C. 1

ii The plateaux are the boiling points of the components. 1Accept equivalent answers referring to energy.



F Test yourselfCompounds and mixtures

1 Rearrange the letters to make the word for a group of atoms in an element or a compound.

O CULL EME

2 Write true or false for each statement.

a Elements, mixtures and compounds are made up of atoms.

b All the atoms in a compound are the same.

c The composition of a compound is fixed but that of a mixture is not.

d A mixture has a fixed melting point.

e In a compound, atoms are joined together.

f The properties of a compound are different from the properties of the

elements it is made of.

3 These observations were made during experiments.

A Some drops of sodium hydroxide solution were added to a brownsolution. A red-brown solid was formed.

B A few crystals of white solid were added to ethanol. The crystals disappeared and a colourless liquid remained.

C Two colourless solutions were mixed and the temperature of the solution fell. Bubbles of a colourless gas were seen.

In which experiments is a chemical reaction likely to have taken place?

4 Rearrange the letters to give the names of three methods of separatingchemicals.

LOT D INITIALS

E TRIFLING

VA OPERATION

5 After each substance, write whether it is an element, a mixture or a compound.

oxygen air

liquid air pure water

mineral water sea water

copper


Test-Qust.qxd 22-Oct-03 3:58 PM Page 11

F Test yourselfCompounds and mixtures (continued)

6 Amy has two bottles containing the same chemical. In bottle X thechemical is pure and in bottle Y the chemical is impure.Tick the statement that is true.

Both melt at the same fixed temperature.

X melts at a lower temperature than Y.

Both melt over the same range of temperature.

7 The formula for glucose is C6H12O6.

a Is glucose an element, a mixture or a compound?

b How many different elements are there in a molecule of glucose?

c How many carbon atoms are there in a molecule of glucose?

d How many hydrogen atoms are there in a molecule of glucose?

e How many oxygen atoms are there in a molecule of glucose?

8 Aluminium nitrate has the formula Al(NO3)3.

a Is aluminium nitrate an element, a mixture or a compound?

b How many elements are there in the formula for aluminium

nitrate?

c How many aluminium atoms are there in the formula for

aluminium nitrate?

d How many nitrogen atoms are there in the formula for

aluminium nitrate?

e How many oxygen atoms are there in the formula for

aluminium nitrate?


Test-Qust.qxd 22-Oct-03 3:58 PM Page 12

FTest yourself

AnswersCompounds and mixtures

1 Rearrange the letters to make the word for a group of atoms in an element or a compound.

O CULL EME

2 Write true or false for each statement.

a Elements, mixtures and compounds are made up of atoms.

b All the atoms in a compound are the same.

c The composition of a compound is fixed but that of a mixture is not.

d A mixture has a fixed melting point.

e In a compound, atoms are joined together.

f The properties of a compound are different from the properties of the

elements it is made of.

3 These observations were made during experiments.

A Some drops of sodium hydroxide solution were added to a brownsolution. A red-brown solid was formed.

B A few crystals of white solid were added to ethanol. The crystalsdisappeared and a colourless liquid remained.

C Two colourless solutions were mixed and the temperature of thesolution fell. Bubbles of a colourless gas were seen.

In which experiments is a chemical reaction likely to have taken place?

4 Rearrange the letters to give the names of three methods of separating chemicals.

LOT D INITIALS

E TRIFLING

VA OPERATION

5 After each substance, write whether it is an element, a mixture or a compound.

oxygen air

liquid air pure water

mineral water sea water

copper element

mixturemixture

compoundmixture

mixtureelement

EVAPORATION

FILTERING

DISTILLATION

A and C

true

True

false

true

false

true

MOLECULE


Test-Ans.qxd 22-Oct-03 4:03 PM Page 11

FTest yourself

AnswersCompounds and mixtures (continued)

6 Amy has two bottles containing the same chemical. In bottle X thechemical is pure and in bottle Y the chemical is impure.Tick the statement that is true.

Both melt at the same fixed temperature.

X melts at a lower temperature than Y.

Both melt over the same range of temperature.

7 The formula for glucose is C6H12O6.

a Is glucose an element, a mixture or a compound?

b How many different elements are there in a molecule of glucose?

c How many carbon atoms are there in a molecule of glucose?

d How many hydrogen atoms are there in a molecule of glucose?

e How many oxygen atoms are there in a molecule of glucose?

8 Aluminium nitrate has the formula Al(NO3)3.

a Is aluminium nitrate an element, a mixture or a compound?

b How many elements are there in the formula for aluminium

nitrate?

c How many aluminium atoms are there in the formula for

aluminium nitrate?

d How many nitrogen atoms are there in the formula for

aluminium nitrate?

e How many oxygen atoms are there in the formula foraluminium nitrate? 9

3

1

3

compound

6

12

6

3

compound

✓


Test-Ans.qxd 22-Oct-03 4:03 PM Page 12

FEnd of unit test

GreenCompounds and mixtures

1 Sam has a solution which contains a solid dissolved in ethanol.

Ethanol has a boiling point of 78 °C.

Sam tries to get some ethanol from the solution using theapparatus in the diagram.

a Which label, A, B, C or D shows where the solution is placed? 1 mark

b Which label, A, B, C or D shows where the ethanol is collected? 1 mark

c What is the temperature on the thermometer when the ethanol is collected? 1 mark

d What is the name of the process taking place? 1 mark

Choose from this list.

2 The table gives some information about three substances.

You have been given a mixture of powdered X, Y and Z.You add the mixture to ethanol and stir.

a Write the letter of the substance which dissolves in alcohol. 1 mark

The solids that did not dissolve in ethanol were than added to water.The mixture was stirred. The solution was filtered.

b Write the letter of the substance collected on the filter paper. 1 mark

c i Write the letter of the substance with good solubility in water. 1 markii How could you get this substance as a solid from the solution? 1 mark

A

C

B

D

heat


Substance State at room Solubility in Solubility in temperature water ethanol

X solid good poor

Y solid poor good

Z solid poor poor

chromatography combustion distillation filtration

D-F-EUTest.qxd 25-Nov-03 8:46 AM Page 16

FEnd of unit test

GreenCompounds and mixtures (continued)

3 The bar chart shows the melting and boilingpoints of various metals.

a Which metal boils at 357 °C? 1 mark

b Which metal melts at 63 °C? 1 mark

c Name one metal that would change state between 0 °C and 400 °C. 1 mark

d Which metal is shown as a gas, a liquid anda solid on the bar chart? 1 mark

4 Copper and sulphur are two elements.

a What is the name for the smallest particle ofcopper or sulphur that can exist?

Choose from this list. 1 mark

When a mixture of copper and sulphur is heated together, themixture turns black and glows. It carries on glowing when theflame is removed. A compound is formed with the formula CuS.

b How many atoms of copper and of sulphur are there in amolecule of CuS? 1 mark

c Copy and complete this diagram by drawing one moleculeof CuS. 2 marks

5 Air is composed of many gases.

a Which gas makes up 21% of air? 1 mark

b What sort of particles is this gas made of? 1 mark

Pure oxygen is made from air. The air is cooled to −200 °C. This means all the nitrogen and all the oxygen will have condensed. It will be liquid air.

copper

+

sulphur mixture ofcopper and

sulphur

compoundof copper

and sulphur

1000 °C

pot

assi

um

alum

iniu

m

gold

mer

cury

tin lead

iron

cop

per

900 °C

800 °C

700 °C

600 °C

500 °C

400 °C

300 °C

200 °C

100 °C

0 °Cgas liquid solid

25 °C


an atom a formula a molecule


FEnd of unit test

GreenCompounds and mixtures (continued)

Nitrogen boils at −196 °C. Oxygen boils at −183 °C.

c If liquid air is heated up from −200 °C, which gas will boilaway first? 1 mark

d Liquid air has more than one boiling point. Write the letterthat best describes air:

A an elementB a compoundC a mixtureD a molecule. 1 mark

6 A solid acid is heated until it melts. This liquid is then left to cool to room temperature. The temperature is taken every minute.

a Which factor in the experiment is the dependent (outcome) variable (the one that will be measured to collect the results)? 1 mark

b The graph can be used to find the melting point of the acid. Which part of the graph would show this? 1 mark

c Between which two temperatures was the experiment carried out? 1 mark

d The temperature could have been taken every five minutes. Why would this not be a good idea? 1 mark

e The acid was heated in a test-tube in a water bath. Why is this safer than heating over a Bunsen flame? 1 mark

Tem

per

atu

re (

°C)

300

Time (minutes)1 2 3 4 5 6 7 8 9 10 11 12

40

50

60

70

80

90



FEnd of unit test

RedCompounds and mixtures

1 The table gives informationabout the melting points and boiling points of gases in the air.

The air is dried before beingseparated into its constituentgases.

a Which substance in dried air is a compound and a gas at room temperature? 1 mark

b What name is given to the process used to separate air into itsconstituent gases? Choose from this list. 1 mark

Air can be separated into its constituents by cooling the mixture to −200 °C.

c Stage 1: two gases are removed from dried air before cooling itor they would solidify and block the pipes. Which gases are these? 1 mark

d Stage 2: the mixture is cooled. Two gases have not liquefied at−200 °C. Which gases are these? 1 mark

e Stage 3: there are two substances remaining in the liquidmixture. Which two substances are these? 1 mark

f Stage 4: the liquid mixture is allowed to warm up now. Thetwo liquefied gases in it boil off at different temperatures.Which one boils off first? 1 mark

2 When a mixture of cooper and sulphur is heated together, themixture turns black and glows. It carries on glowing when theflame is removed. A compound is formed with the formula CuS.

a Write down the name of the compound formed. 1 mark

b How many atoms of copper and sulphur are there in amolecure of CuS? 1 mark


Gas Melting point Boiling point (°C) (°C)

nitrogen −210 −196

oxygen −218 −183

carbon dioxide −79 −57

water 0 100

argon −189 −186

neon −249 −246

helium −272 −269

distillation evaporation filtration


FEnd of unit test

RedCompounds and mixtures (continued)

c Copy and complete thisdiagram by drawing one molecule of CuS. 2 marks

d Write a word equation for the reaction between copper and sulphur. 1 mark

3 Air is composed of many gases.

a Which gas makes up 21% of air? 1 mark

b What sort of particles is this gas made of? 1 mark

Pure oxygen is made from air. The air is cooled to −200 °C. Thismeans all the nitrogen and all the oxygen will have condensed.It will be liquid air.

Nitrogen boils at −196 °C. Oxygen boils at −183 °C.

c If liquid air is heated up from −200 °C, which gas will boilaway first? 1 mark

d Liquid air has more than one boiling point. Write the letter thatbest describes air:

A an elementB a compoundC a mixtureD a molecule. 1 mark

4 The table gives some information aboutsome substances.

a Why does the data in the table suggest that lead bromide is a compound rather than a mixture? 1 mark

b Why does the data suggest that solder is a mixture of tin and lead rather than acompound of tin and lead? 1 mark

c Lead nitrate has a formula Pb(NO3)2. Write down the ratio ofthe different types of atom present in the compound. 1 mark

copper

+

sulphur mixture ofcopper and

sulphur

compoundof copper

and sulphur


Substance Melting point (°C)

lead 327

tin 232

lead bromide 373

solder 80– 150


FEnd of unit test

RedCompounds and mixtures (continued)

5 a The diagram below shows a molecule of ammonia. How manyof each type of atom are present in the molecule? 1 mark

b The diagram below shows a molecule of methane. Write downthe chemical formula of methane. 1 mark

6 A solid acid is heated until it melts. This liquid is then left to coolto room temperature. The temperature is taken every minute.

a Between which two temperatures was the experiment carriedout? 1 mark

b The temperature could have been taken every five minutes. Why would this not be a good idea? 1 mark

c The acid was heated in a test tube in a water bath. Why is this safer than heating over a Bunsen flame? 1 mark

d To the nearest minute, how long did it take for the liquid tobecome solid? 1 mark

e Why does the temperature axis of the graph not start at 0 °C? 1 mark

Tem

per

atu

re (

°C)

300

Time (minutes)1 2 3 4 5 6 7 8 9 10 11 12

40

50

60

70

80

90

C

HH

HH

NH

H

H



FEnd of unit test

mark schemeCompounds and mixtures


Green (NC Tier 3–6)Question Answer Mark Level

1 a A 1 3

b C 1 3

c 78 °C 1 4

d Distillation 1 4

2 a Y dissolves and X and Z do not. 1 5

b Z 1 5

c i X 1 5

ii Let the water evaporate or evaporation. 1 5

3 a Mercury 1 4

b Potassium 1 4

c One from: potassium, mercury, tin, lead. 1 5

d Potassium 1 5

4 a An atom. 1 4

b One atom of copper and one atom of sulphur. 1 5

c

One atom of copper and one atom of sulphur. 1 5Atoms joined. 1 5

5 a Oxygen 1 5

b Molecules 1 5

c Nitrogen 1 6

d C 1 6

6 a Temperature 1 4

b Horizontal part. 1 4

c Between 86 °C and 30 °C. 1 5

d Results less reliable/would miss important measurements. 1 5

e Less likely to catch fire/spurt out of end of tube. 1 5

Cu S

Scores in the range of: NC Level

4–7 3

8–13 4

14–17 5

18–25 6


FEnd of unit test

mark schemeCompounds and mixtures


Red (NC Tier 4–7)Question Answer Mark Level

1 a Carbon dioxide 1 4

b Distillation 1 4

c Carbon dioxide and argon. 1 6

d Helium and neon. 1 6

e Nitrogen and oxygen. 1 5

f Nitrogen. 1 6

2 a Copper sulphide 1 5

b One atom of copper and one atom of sulphur. 1 5

c

One atom of copper and one atom of sulphur. 1 5Atoms joined. 1 5

d Copper + Sulphur → Copper sulphide 1 6

3 a Oxygen 1 5

b Molecules 1 5

c Nitrogen 1 6

d C 1 6

4 a Fixed melting point. 1 7

b Melts over a range of temperature. 1 5

c Lead 1: nitrogen 2: oxygen 6. 1 5

5 a Nitrogen 1, hydrogen 3. 1 5

b CH4 1 7

6 a Between 86 °C and 30 °C. 1 5

b Results less reliable/would miss important measurements. 1 5

c Less likely to catch fire/spurt out of end of tube. 1 5

d 3 1 6

e Experiment does not go to this temperature/this is belownormal room temperature. 1 6

Cu S

Scores in the range of: NC Level

5–9 4

10–15 5

16–19 6

20–25 7


F Pupil checklistCompounds and mixtures


Learning outcomes I can do I can do I need to this very this quite do more well well work on this

I can describe to someone else thedifference between a compound and amixture using my ideas about atoms.

I can explain to someone the differencebetween atoms and molecules.

I can identify at least three ways torecognise a chemical reaction is takingplace.

I can use my ideas of atoms to describewhat happens when chemicals react toform new substances.

I can describe how a scientist uses theword pure.

I can explain why mixtures do not havemelting points and boiling points.

I can use the chemical formula of acompound to identify and describe theratio of atoms in it.

I can provide evidence to show that theamount of magnesium and oxygen inmagnesium oxide is a fixed ratio.

Pupil checklist.qxd 12-Nov-03 8:56 AM Page 6

F GlossaryCompounds and mixtures


Word

composition R

fixed composition R

hydrogen peroxide

mixture

precipitate

products

pure

ratio

reactants

Definition

A compound containing two hydrogen and two oxygenatoms.

A material that contains only one substance.

The substances that take part in a chemical reaction to formthe products.

The new substances that are formed in a chemical reaction.

A solid made when two liquids react.

A material that contains more than one substance.

Always made from the same atoms, present in the sameratio. R

The parts something is made from. R

A way of showing a scale factor. For example, a scale of 1:10means you have to multiply your number or measurementby 10 to get the real measurement.

Glossary.qxd 12-Nov-03 8:24 AM Page 11

F Key wordsCompounds and mixtures

composition R

fixed composition R

hydrogen peroxide

mixture

precipitate

products

pure

ratio

reactants

composition R

fixed composition R

hydrogen peroxide

mixture

precipitate

products

pure

ratio

reactants

Sheet 1 of 1

Sheet 1 of 1


Key wordsF Compounds and mixtures


Keywords.qxd 12-Nov-03 8:28 AM Page 6


F Book answersCompounds and mixtures

F1 Compounds all aroundGreena twob It is made up of more than one type of atom

joined together.c The water molecule is made of two hydrogen

atoms joined to one oxygen atom. Thehydrogen peroxide molecule is made of twohydrogen atoms joined to two oxygen atoms.

d It is made of two different kinds of atomsjoined together.

e saltf It has no hazard label on it.1 Compounds are shown by ... formulae.

All pure substances have known ... meltingpoints and boiling points.Elements are shown by ... symbols.Compounds have different properties ... fromthe elements that made them.

2

Reda twob It is made up of more than one type of atom

joined together.c The water molecule is made of two hydrogen

atoms joined to one oxygen atom. Thehydrogen peroxide molecule is made of twohydrogen atoms joined to two oxygen atoms.

d i twoii three

iii twoe Boiling points: sodium 883°C, chlorine –35°C,

sodium chloride 1413°C1 A – NO2, B – CH4, C – NH3

2 a i

ii

b sodium + chlorine → sodium chloride c The new substance is completely different from

the elements from which it was made.

F2 Reacting compoundsGreena Heat energy was given out.b i Zinc and copper oxide.

ii Copper and zinc oxide.c Copper oxide is made of alternating copper and

oxygen atoms. Zinc oxide is made ofalternating zinc and oxygen atoms.

d Zinc was one of the reactants.e The copper atoms came from the copper oxide

compound and were left uncombined.f A new substance was formed and energy was

given out.g sodium iodide + lead nitrate → sodium nitrate +

lead iodide

Substance sodium chlorine sodiumchloride

Element or element element compoundcompound?

Symbol or Na Cl NaClformula

Solid, liquid solid gas solidor gas?

Colour silver green colourless

Melting 98° –101° 801°point in °C

Sodium Sodium chloride

element compound

symbol Na formula NaCl

metal non-metal

shiny, silvery colourless, harmlesscrystals

melting point 98°C melting point 801°C

boiling point 883°C boiling point 1413°C

Reacts with hydrochloric Doesn’t react withacid to make hydrogen. hydrochloric acid.

Chlorine Sodium chloride

element compound

symbol Cl formula NaCl

non-metal non-metal

green poisonous gas colourless, harmlesscrystals

melting point –101°C melting point 801°C

boiling point –35°C boiling point 1413°C

Doesn’t react with Doesn’t react withhydrochloric acid. hydrochloric acid.

Book Answers.qxd 25-Nov-03 8:40 AM Page 16


F Book answersCompounds and mixtures (continued)

h i The lead atoms that made the lead iodidecame from the lead nitrate.

ii The iodine atoms that made the lead iodidecame from the sodium iodide.

iii Bubbles were given out.1 a zinc + copper oxide → zinc oxide + copper

b hydrogen peroxide + pea cells → water +oxygen

2 a sodium iodide + lead nitrate → lead iodide +sodium nitrate

b zinc + copper oxide → zinc oxide + copperc The pea in a solution of hydrogen peroxide.d sodium iodide + lead nitrate → lead iodide +

sodium nitrate

Reda Thermal (heat) energy was given out.b i Zinc and copper oxide.

ii Copper and zinc oxide.c Zinc was one of the reactants.d The copper atoms were left uncombined after

the reaction.e A solid was formed; a colour change occurred.f sodium iodide + lead nitrate → lead iodide +

sodium nitrate g Sodium chloride reacts with lead nitrate to form

lead chloride and sodium nitrate.h Bubbles are given out.1 a The reaction of lead nitrate with sodium

iodide.b The reaction of zinc with copper oxide.c A pea put into hydrogen peroxide.d The reaction of lead nitrate with sodium

iodide.e There is no reaction described in these pages

which shows a reaction where energy is takenin.

2 a i H2O2ii H2O

iii C6H12O6b oxygenc i four

ii fourd The total number of hydrogen atoms remains

the same.

F3 What’s in it?Greena Any three from: Ca, Mg, Na, K, HCO3, Cl, SO4, F,

Fe, Al, NO3b saltc The tap water is heated until it boils. The water

turns into steam, leaving any other substancesbehind. The steam is collected and condensedback into liquid water.

d Yes. All the other substances are left behind.1 a A, D, E

b B, C, F

c A, Ed D

2 a falseb falsec falsed truee false

Reda Any three from: Ca, Mg, Na, K, HCO3, Cl, SO4, F,

Fe, Al, NO3b saltc i 130mg

ii 13mgd Yes. All the other substances are left behind.e Calcium chloride contains one atom of calcium

and two atoms of chlorine.1 a false

b falsec falsed falsee truef true

2 Filtration, evaporation, distillation andchromatography.

3 a A, D, Eb B, C, Fc A, Ed D

F4 The air around usGreena i nitrogen

ii oxygenb i Oxygen, hydrogen, nitrogen and carbon

dioxide.ii argon

c nitrogen1 Mixtures do not have ... one melting point or

one boiling point.Pure substances have ... only one substancepresent.

2 a A is nitrogen and B is air.b Nitrogen is a pure substance so it gives only

one peak. Air is a mixture so it gives morethan one peak.

Reda i Oxygen, hydrogen, nitrogen and carbon

dioxide.ii argon

b Air is a mixture of the gases nitrogen (78%),oxygen (21%), carbon dioxide (0.4%) and theother remaining gases (less than 1%).

c Air near a bonfire will contain more carbondioxide and some smoke. Air in a meadow will



F Book answersCompounds and mixtures (continued)

contain the chemicals made by flowers to attractbees. Air in a crowded lift will contain lessoxygen than the air in an empty lift becausepeople will be taking oxygen out of the air.

d When nitrogen is cooled, only one liquidcondenses at one temperature. When air iscooled, several liquids condense at differenttemperatures.

e There may be two different gases whichcondense at the same temperature.

f i –196°Cii –183°C

1 a A is nitrogen and B is air.b Nitrogen is a pure substance so it gives only

one peak. Air is a mixture so it gives morethan one peak.

2 a Air is cooled until a liquid condenses, atwhich point the temperature remainsconstant until all of that particular gas hasturned to liquid. The first gas to condensewould be oxygen at –183°C. Cooling thencontinues until the temperature reaches theboiling point of the next gas. Thetemperature then remains constant whilethis gas liquefies. When that gas has allturned to liquid, the temperature becomeslower again, and so on.

b To obtain pure gases. Liquid nitrogen isuseful to preserve human cells and tissue.Pure oxygen is used in hospitals.

F5 FormulaeGreena calcium : oxygen

20:201:1

The formula is CaO.b aluminium : chlorine

6:181:3

The formula is AlCl3.c sodium : nitrogen

36:123:1

The formula is Na3N. d 200 chlorine atoms.e One million sodium atoms.f Three billion chlorine atoms.g Two trillion oxygen atoms.1 a Diagram of MgO as diagram of CaO on page

65.b Diagram of MgCl2 as diagram of CaCl2 on

page 64, with Mg replacing Ca.2 a Diagram of SO2 as diagram of Na2O on page

64, with S replacing O and O replacing Na.

b Diagram as:

with differently sized and coloured circlesinstead of letters.

c Diagram as:

with differently sized and coloured circlesinstead of letters.

d Diagram of N2O as diagram of Na2O on page 64,with N replacing Na.

Reda iAlCl3 ii Na3N iii Al2O3b i 20 million chlorine atoms.

ii 300 billion atoms of oxygen.c The third result: 3g of magnesium reacted with

0.35g of oxygen.d i 2.00g (± 0.05g)

ii 4.00g (± 0.05g)iii 6.00g (± 0.05g)

e 3:21 a Diagram of MgO as diagram of NaCl on page

64.b Diagram of MgCl2 as diagram of Na2O on

page 64, with Mg replacing O and Clreplacing Na.

c Diagram of Mg3N2 as diagram of Al2O3 onpage 64, with Mg replacing O and Nreplacing Al.

2 a Diagram of SO2 as diagram of Na2O on page64, with S replacing O and O replacing Na.

b Same diagram as Green question 2b above.

c Same diagram as Green question 2c above.

d Diagram of N2O as diagram of Na2O on page64, with N replacing Na.

3 a Mass of magnesium.b Mass of magnesium oxide.c Subtract the mass of magnesium used from

the mass of magnesium oxide formed.d Either the magnesium had not all been

burned or some of the magnesium oxide waslost before weighing.

CH

H

H

C H

H

H

CH H

H

H


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