90 Materials 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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Unit 6M.2 Making pure substances from mixtures · 91 Materials Grade6, Unit 6M.2: Making pure substances from mixtures Making pure substances from mixtures You can make a Usolution
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90
Materials
Grade6, Unit 6M.2: Making pure substances from mixtures
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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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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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.
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.
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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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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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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:
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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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?
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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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.