elements, compounds and mixtures. matter can be classified into elements, compounds, mixtures. try...
TRANSCRIPT
Elements, Compounds and
Mixtures
Matter can be classified into Elements, Compounds, Mixtures.
Try classifying the following :
rust milk gold
Stew stew sulfur salt
Sugar pizza air
compound mixture element
mixture element compound
compound mixture mixture
ElementsAn element is a pure substance that cannot be broken down into any simpler substance by chemical methods/reactions
It is therefore the basic building block of matter
Examples of elements
Silver Carbon Bromine
Sulfur Mercury Chlorine
What are their state of matter?
Are they metals or non-metals?
Facts about ElementsMore than 100 elements
The most abundant element in the universe is hydrogen
The most abundant element in air is nitrogen
The most abundant element in the Earth’s crust and our body is oxygen
Oxygen can be found
As free oxygen in the atmosphere
In compound in the earth crust (metal ores)
Iron oresMagnetite Fe3O4
Haematite Fe2O3
Siderite FeCO3
Aluminium OreBauxite Al(OH)3
Combined with hydrogen as water
The following table gives the approximate analysis of a human
bodyElement Percent by mass
Oxygen (O) 65
Carbon (C) 18
Hydrogen (H) 10
Nitrogen (N) 3
Calcium (Ca) 1.5
Phosphorus (P) 1.2
Potassium (K) 0.2
Sulfur (S) 0.2
Chlorine (Cl) 0.2
Sodium (Na) 0.1
Magnesium (Mg) 0.05
Iron (Fe), Zinc (Zn), Iodine (I) <0.05 each
Selenium (Se), Fluorine (F) <0.05 each
Alphabetical Symbols are Used to Represent Elements
Symbols for the Elements
chemical symbol isfirst letter of itsname
Hydrogen (H)Carbon (C)Oxygen (O)Fluorine (F)Iodine (I)
chemical symbol consists of 2 letters
Chlorine (Cl)Helium (He)Beryllium (Be)Magnesium (Mg)Calcium (Ca)
chemical symbol comesfrom names in other languages
Copper (Cu-cuprum )[Latin]Iron (Fe-ferrum) [Latin]Tungsten (W–wolfram) [German]Silver (Ag-Argentum) [Latin]Tin (Sn-Stannum) [Latin]Gold (Au-Aurum) [ Latin]Lead (Pb-Plumbum) [Latin]
Name Symbol Name Symbol
Hydrogen H Aluminium Al
Carbon C Calcium Ca
Nitrogen N Iron Fe
Sulfur S Tungsten W
Chlorine Cl Copper Cu
Some Symbols of Elements
We can Classify Elements
A) By State of Matter
B) As Metals or Non-metals
C) As in the Periodic Table
Classifying the Elements
A) Classifying Elements by State
Elements
Solids Liquids Gases
MercuryBromine
Hydrogen HeliumNitrogen NeonOxygen ArgonFluorine Krypton Chlorine Xenon Radon
All others
Classifying the Elements
B) Classifying Elements as Metals and Non-metals
Elements
Metals Non-metals
Elements to the left ofthe zigzag line in the Periodic Table
Elements to the right ofthe zigzag line in the Periodic Table
B) Classifying Elements as Metals and Non-metals
Property Metal Non-metalAppearance
Shiny-usually solid
Dull-usually solid, liquid or gas
Strength Usually strong :Malleable (can be
beaten into any shape) &
Ductile (can be pulled into wires)
Usually weak (brittle)
Hardness Usually hard Usually soft
Density Usually high Usually low
B) Classifying Elements as Metals and Non-metals
Property Metal Non-metalMelting/boiling point
Usually high Usually low
Heat conductivity
Usually good conductor
Usually poor conductor
Electrical conductivity
Usually good conductor
Usually poor conductor
Experimentto test electricalconductivity
Arranging the Elements As you know, the elements are arranged in the Periodic Table.
The elements were first arranged in this way by Dmitri Mendeleev, a professor at St. Petersburg University, in 1869. His arrangement was based on atomic mass.
When Mendeleev was setting out the table, only 63 elements had been discovered. His big idea was to leave gaps for yet to be discovered elements. He was able to predict the properties of some of these elements, including silicon and boron. When his predictions were shown to be accurate his table became accepted, and it is the basis of the one we use today.
‘Maybe one day we’ll understand why Dmitri always lays out his blocks this way!’
All the elements discovered are placed in thePeriodic Table of elements :
Classifying the Elements
C) Classifying Elements as in the Periodic Table
Group -- The vertical column of the Periodic Table
Elements in the same group have the similar chemical
properties.
E.g. Lithium, Sodium, Potassium, Rubidium, Caesium &
Francium – all reactive metals are in Group I.
Classifying the Elements
C) Classifying Elements as in the Periodic Table
Period -- The horizontal row of the Periodic Table
Properties of the elements change gradually (from
metallic to non-metallic) across a period from the left to
the right of the Periodic Table.
E.g. Lithium, Beryllium, [metals]
Boron, [metalloid]
Carbon, Nitrogen, Oxygen, Fluorine and Neon [non-metal]
are in Period 2.
The Modern Periodic Table
Group -- The vertical column of the Periodic Table
Period -- The horizontal row of the Periodic Table
Period 1
Period 2
Period 3
Uses of ElementsElement Use Property
Diamond (a form of carbon)
To cut other materials
Very hard
Copper To make water pipes
Strong; does not corrode easily
Silver To plate onto glass as mirror
Reflect light
Uses of ElementsElement Use Property
Silicon To make electronic parts for radios, televisions and computers
Semi-conductor
Helium To fill balloons, weather balloons, airships
Very light and does not burn
Graphite (a form of carbon)
To make pencil lead
Soft and slippery
Element Use Property
Neon To make neon lights, advertising signs
Inert
Hydrogen To produce water and energy in space crafts
Very light and colourless
Coal (a form of carbon)
Primary Fuel Hard and Brittle
CompoundsA compound is a pure substance consisting two or more elements chemically combined together
Matter
Pure substances Impure substances(Mixtures)
Elements Compounds
Examples of Compounds
Compound Formulae of Compounds
Elements present
Pure Sand SiO2Silicon and Oxygen
Water H2O Hydrogen and Oxygen
Glucose C6H12O6Carbon, Hydrogen and Oxygen
Sodium Chloride
NaCl Sodium and Chloride
Calcium Carbonate
CaCO3Calcium, Carbon and Oxygen
Characterisitics of CompoundsA) Compounds are formed during chemical reactions
During the formation of compounds, a lot of energy, usually in the form of heat and/or light, is given out or taken in from the surroundings.
E.g. Oxygen and hydrogen combine chemically to form water, a lot of energy is released. This is made use of to launch rockets and space shuttles into space.
B) A compound can only be broken down into simpler substances by chemical reactions. (Cannot be broken down by physical methods) Compounds can be decomposed by heating, exposure to light or passing an electric current through it.
E.g. By passing electricity(electrolysis), water(compound) breaks down into hydrogen(element) and oxygen(element).
C) A compound has properties which are different from those of its constituents.
E.g. Sodium is a soft, silvery metallic solid while chlorine is a poisonous greenish yellow gas at room temperature. Sodium chloride in contrast, is a white crystalline solid which is edible.
A soft silvery metallic solid
A greenish-yellow toxic
gas
A white crystalline edible
solid
D) The constituent elements in a compound are joined in a fixed proportion by mass. E.g. During the formation of water, 1 g of hydrogen gas combines with 8 g of oxygen gas to form 9 g of water.
hydrogen + oxygen water
1g 8g 9g
4g 32g 36g
5g 8g 9g
1g 10g 9g
Mixtures
Matter
Pure substances Impure substances(Mixtures)
Elements Compounds
What is a Mixture?
It is not found in the Periodic Table
It is not a pure substance (unlike Elements or Compounds)
It is made up of two or more substances (elements or compounds or both) not chemically joined together (physically mixed together)
Examples of MixturesA) Mixtures of ElementsE.g. Alloys are mixtures of two or more metals, or one metal and a small amount of non-metal.
Steel: Iron, nickel and chromium etc
Cast iron: Iron and carbon
Brass: Copper and zinc
Bronze: Copper and tin
Examples of MixturesB) Mixtures of CompoundsE.g. Seawater is a mixture of compounds such as salt dissolved in water.E.g. Crude oil is mixture of compounds such as kerosene, diesel oil, petrol, lubricating oil etc
Examples of MixturesC) Mixtures of Elements and Compounds
E.g. Air is a mixture of gases. Some of these gases such as oxygen and nitrogen are elements. Other gases such as carbon dioxide and water vapour, are compounds.
O2 N2 CO2 H20
Examples of MixturesC) Mixtures of Elements and Compounds
E.g. Air is a mixture of gases. Some of these gases such as oxygen and nitrogen are elements. Other gases such as carbon dioxide and water vapour, are compounds.
O2 N2 CO2 H20
Characterisitics of MixturesA) No chemical reaction takes place when mixture is formed
This also means that no heat and/or light, is given out or taken in from the surroundings.
E.g. When the different gases that make up air are mixed, no chemical reaction take place. No energy, in the form of heat or light, is taken in and given out
Characterisitics of MixturesB) A mixture can be separated into its constituents by physical methods such as filtration, evaporation and distillation
E.g. Iron filings can be separated from mixture of iron filings and sulfur using magnet.
Characteristics of MixturesC) A mixture can be separated into its components by physical means
E.g. Salt can be obtained from sea-water by evaporating sea-water to dryness
E.g. Sugar can be obtained from sugar solution by crystallisation
Characterisitics of MixturesC) A mixture has the properties of its constituents
E.g. Air is colourless, like the colourless gases that make up airE.g. Air support burning just like oxygen gas present in it
Characterisitics of MixturesD) The constituents in a mixture can be mixed in any proportions
E.g. Composition of air varies at different altitudes and air in forested areas will have a higher percentage of oxygen compared to air in industrial areas
Heating iron and sulfurtogether (chemicalreaction occurs)
Mixing iron and sulfurtogether (no chemicalreaction occurs)
Iron can beseparated from sulfur using magnet(a physical method)
Can iron sulfide be separatedout using magnet?
A compoundis formed
A mixtureis formed
Mixture can be separatedby physical method No. Chemical
method needed
compound mixture
Properties ?
has properties that are different from the properties of its constituent elements
has the properties of the substances that make it up
Differences between Compounds & Mixtures
compound mixture
How are they formed?
formed by a chemical reaction between its elements with heat or light taken in or given out
Note: chemical reaction is not the same as chemical method/means
no heat or light is taken in or given out since no chemical reaction is involved
Differences between Compounds & Mixtures
How are they broken down or separated?
can only be broken down into simpler substances by chemical methods such as heating or by passing electricity[physical methods cannot break down compounds]Note :chemical reaction is not the same as chemical method/means
can be separated into its components by physical means
[there is no need to use chemical methods to separate mixtures]
compound mixtureDifferences between Compounds & Mixtures
How are they formed?
The different elements in a compound are joined together in a fixed proportion by mass
The substances in a mixture can be mixed in any proportion
compound mixture
Differences between Compounds & Mixtures
Are these Compounds or Mixtures ?
blood milk tomato sauce
air petrol sugar
carbon dioxide ink sea-water
sugar solution sand-water suspension
Thinking Question ……..A student carried out the following experiment to investigate the effect of heat on a mixture of iron and sulfur. After heating for a few minutes, the mixture began to glow brightly. The glow spread through the contents of the tube after heating was stopped. When the tube had cooled the contents were tipped out onto a heat–resistant bench mat. A black solid has been formed.Write down two pieces of information from the description of the experiment which suggests that the new substance formed after heating is a compound.
Thinking Question …….. Ans
A student carried out the following experiment to investigate the effect of heat on a mixture of iron and sulfur. After heating for a few minutes, the mixture began to glow brightly. The glow spread through the contents of the tube after heating was stopped. When the tube had cooled the contents were tipped out onto a heat–resistant bench mat. A black solid has been formed.When the new substance is formed, heat and light is given off, indicating chemical reaction between iron and sulfur forming a compound.
The substance formed is a black solid which looks totally different from iron or sulfur.