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Grade6, Unit 6M.2: Making pure substances from mixtures

Unit 6M.2: Making pure substances from mixtures

• Making pure substances from mixtures

• Crystals

Science skills: • Classifying • Observing • Predicting

By the end of this unit you should: Be able to suggest ways of separating dissolved

solids from insoluble solids Know that crystallisation is a way of obtaining

pure solids from solutions

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Materials

Grade6, Unit 6M.2: Making pure substances from mixtures

Making pure substances from mixtures

You can make a Usolution U by dissolving a solid like salt in

water.

The solution looks like pure water because the solid has

broken down into tiny invisible particles.

To make the solid ( UsoluteU) reappear, you can cause the

Usolvent U to UevaporateU, or turn into a gas.

As the liquid disappears, the solid reappears because there

is not enough liquid to dissolve it.

You can get (water) the solvent again by condensation of the

water vapour.

6.11.3, 6.11.4

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Materials

Grade6, Unit 6M.2: Making pure substances from mixtures

How can you separate a mixture of UinsolubleU solids from a

liquid?

UFiltration U is used to separate a mixture of UinsolubleU solid and

a liquid.

The mixture is poured through a Ufilter paper U. Only the liquid passes through, and is called the UfiltrateU.

We can use filter paper or a sieve to separate liquid from solid.

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Materials

Grade6, Unit 6M.2: Making pure substances from mixtures

Activity: Getting a dissolved solid back. Material: Salt- Sugar Warm water A clear plastic tumbler A teaspoon Procedures: 1- Pour warm water into the tumbler until it is one third full. Add a spoonful of salt, stir until all the salt has dissolved. 2- Pour the salt solution into the saucer until there is a shallow pool, then put the saucer on a sunny windowsill or in some other warm, airy place. 3- Check the saucer twice a day for the next two or three days. What do you notice appearing on the saucer as the water gradually disappears? --------------------------------------------------------------------------------------------------

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Materials

Grade6, Unit 6M.2: Making pure substances from mixtures

Activity 2: Filtering through sand You will need A 500 ml plastic drink bottle

• Scissors • Cotton wool • Sand, gravel, pebbles • Potting composite mixed with water • Water

Procedure

1-Cut the bottle in half. 2-Place the funneled end facing downwards into the base of the bottle. 3-Fill the funnel with cotton wool, pebbles, and gravel and sand, as shown, to make your filter. You might need to staple the funnel above the bottom. 4-Pour the composite mixed with water into the bottle and watch it drip through. 5-What color are the drips? --------------------------

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6-How fast is the water passing through?

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Materials

Grade6, Unit 6M.2: Making pure substances from mixtures

Activity: Getting dissolved solute back To obtain the solid from a mixture of sand and water and a salt solution.

Materials

Glass beaker

Measuring cylinder

Spatula

Stirring rod

Funnel

Filter paper

Conical flask

Beaker

Evaporating dish

Hot plate

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Materials

Grade6, Unit 6M.2: Making pure substances from mixtures

Experiment 1: 1-Measure out 25cmP

3P of water into a 100 cmP

3P glass beaker.

2-Add 3 spatulas of sand to the water.

3-Stir the mixture until nothing else happens.

4-Set up the filter funnel, filter paper and conical flask.

5-Pour the sand and water mixture through the filter paper.

6-Write down exactly what happens.

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-----------------------------------------------

Experiment 2: 1-Measure out 25cmP

3 Pof water in a 100cmP

3P glass beaker.

2-Add 3 spatulas of salt to the water.

3-Stir the water until all the salt has dissolved.

4-Set up the filter funnel, filter paper and

conical flask.

5-Pour the salt solution through the filter paper.

6-Write down exactly what happens.

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Materials

Grade6, Unit 6M.2: Making pure substances from mixtures

Experiment 3:

1-Collect the salt solution formed during Experiment2.

2-Pour the salt solution into an evaporating dish.

3-Place the evaporating dish on a hot plate.

4-Write down exactly what happens.

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Conclusion :

1-Name the method that can be used to separate

sand from a mixture of sand and water.---------------

2-Name the method that can be used to separate salt

from a salt solution.

-----------------------------------------------

3-In UExperiment 1U the solid remaining in the filter paper

is called the __________________ .

4. In UExperiment 2U the liquid that passes through the

filter paper is called the ________________ .

5. In UExperiment 3U the water that was in the evaporating

dish goes into the ______________________ .

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Materials

Grade6, Unit 6M.2: Making pure substances from mixtures

Scissors, mixing bowl, jug, funnel, paper towel, gravel

Using the following equipment; draw a diagram to show how you would separate gravel from water, using filtration. You could also make this a flow chart with words.

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Materials

Grade6, Unit 6M.2: Making pure substances from mixtures

It is important when filtering not to over fill the filter paper. Examples of filtration in everyday life:

4- Vacuum cleaner 5- Drinking Water filter

2- Coffee making

1- Water purification

3- Sewage Works purification

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Materials

Grade6, Unit 6M.2: Making pure substances from mixtures

Key idea • We can separate solute from

solution by evaporation and filtration

• Solids that will not dissolve are insoluble. Sometimes they are suspended in the solution (do not fall to the bottom).

Key words • Soluble • Insoluble • Suspended • React • Filtration • Evaporation • Purification • Residue

Project 1- Find a material that will make a good filter. Explain

why you have chosen that material. How could you test it?

• List the equipment you would use. • What would you be filtering? Choose some

different mixtures. • What would you measure to test the

effectiveness of the filter? 2- Filtering is an important part of the process used to

purify drinking water. Find out what material is used as a filter in water filtration plant. (You may be surprised!!) What is used in Qatar? What is used in other countries?

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Materials

Grade6, Unit 6M.2: Making pure substances from mixtures

Key question 1-Filtration using the equipment shown can be used to separate which materials? A.A solution of copper sulfate and water. B. A solution of sodium chloride and water. C. A mixture of alcohol and water. D.A mixture of mud and water. E. A mixture of sand and sawdust. 2- Describe how you would separate the following mixtures A.A mixture of sand and iron filing : ----------------------------- B. A mixture of sand and pebbles.: -------------------------------- C. A mixture of sand and salt: ----------------------------------------------------------------------------------------------------------------

3-Jamal put 10 cm3 of water and 3g of a different solid into each of four test-tubes. He shook each test-tube. The drawing shows the test-tubes after 10 minutes.

a. Why can the sugar and salt no longer be seen in test- tubes A and C?

--------------------------------------A sugar B limestone C salt D sand

b. If one of the solids was a mixture of salt and sand, what would Jamal see in the tube after 10 minutes? How would Jamal get from the tube (i) some pure sand and (ii) some pure salt?

(i) ------------------------------------(ii)---------------------------

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Materials

Grade6, Unit 6M.2: Making pure substances from mixtures

Crystals

Examples: 0Tquartz 0T, 0Trock candy 0T, 0Thalite0T

Natural crystals: Natural crystals are dug out of the ground,

where the earth's temperature and pressure cause them to

form.

Sugar Crystals Salt sugar

USynthetic crystals

Zincite Crystal Quartz Crystal

6.11.5

A crystal: consists of matter that is formed from an ordered arrangement of atoms, molecules, or ions.

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Materials

Grade6, Unit 6M.2: Making pure substances from mixtures

Observe the pictures of crystals.What do you observe?

• The sides of crystals are flat and smooth;

• Crystals have a regular shape;

• All crystals of the same substance have fundamentally

the same shape.

• Crystals are a pure single substance.

Crystal can be cleaved easily (such as Iceland spar or mica).

When crystals are cleaved the new faces are always parallel

to the old ones.

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Materials

Grade6, Unit 6M.2: Making pure substances from mixtures

Growing Crystals

Do you want to grow great crystals? These are general

instructions for growing crystals that you can use for most

crystal recipes.

Obtain pure sample of a solute from a solution: Growing crystals Procedure: 1-Half fill a tumbler with warm water. 2-Stir in sugar until no more will dissolve, and then pour the clear solution into the other tumbler, leaving any undissolved sugar behind. 3- Use the pencil and cotton to suspend the paperclip in the solution.

You will need: Sugar

Two clear plastic

tumblers

A Pencil - Cotton

Paperclips

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Materials

Grade6, Unit 6M.2: Making pure substances from mixtures

Look at the paper clip every day for about a week and see what happens. My observation: -------------------------------------------------

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Key words • Crystals • Atoms • Molecules • Ions • Natural

crystals • Synthetic

crystals

Key idea • Natural crystals are dug out of

the ground, where the earth's temperature and pressure cause them to form.

• Crystals are structures that are formed from a regular repeated pattern of connected atoms or molecules.

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Materials

Grade6, Unit 6M.2: Making pure substances from mixtures

Project Crystal gardens

Drop a few coloured crystals into a 40% solution of sodium

silicate (‘water glass’) in a glass container. The crystals grow

in vertical strands. The explanation involves osmosis and is

beyond this grade.