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# Yr7 Solutions

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Separating Mixtures

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### Yr7 Solutions

1. 1. SEPARATING MATERIALS Mixtures of materials can be separated using different methods. The method used depends upon the nature of the mixture to be separated.
2. 2. Sieves are frames with a wire mesh stretched across the frame. The mesh has lots of holes in it. Holes in the mesh
3. 3. Filtering The liquid water passes easily through the tiny holes in the filter paper but the solid specks of gold are too big to pass through the same holes. This means that the gold is collected in the filter paper and the water is collected in the measuring cylinder/
4. 4. Before After
5. 5. Having separated out the solid particles by sieving or filtering, there may be substances dissolved the the filtered liquid – the filtrate. To separate the water from the dissolved substances a different method is needed.
6. 6. EVAPORATION When liquid changes to gas, this is called evaporation. This can be used to separate solids from liquids and also dissolved solids from the solvent. Evaporating water
7. 7. Hot Coffee Water grains What happens to the solid coffee grains when they are put into hot water? Explain your answer
8. 8. Dissolving Some solids like salt when put into water can be seen at first but gradually get smaller and will eventually disappear. The water breaks up the salt into smaller and smaller particles which move around in the water, until they are so small that they cannot be seen - the salt has Dissolved. The liquid is now called a Solution of salt water. Other solids like Chalk are not broken down by water and so do not dissolve but stay solid, as a Suspension in the water.
9. 9. The solid coffee grains dissolve in the hot water. There is now a solution of coffee in the cup. The coffee is now a liquid. What would happen if the cup of coffee was left on a hot radiator for a few hours? What sort of change is this an example of? N
10. 10. DISTILLATION This is a method used to separate liquid mixtures into their different component parts. A liquid mixture is heated in a container such as a test tube or flask until the liquid boils. The gas is passed through a delivery tube into a condenser. This cools the gas causing it to condense. The resulting pure liquid is collected. The other part of the mixture is left in the container.
11. 11. Separating a mixture of water and ink by Distillation B C Water + ink Beaker A Heat Water D Explain what is happening at each stage A - D N
12. 12. Separating a mixture of water and ink by Distillation B evaporation of water C – condensation of water Water + ink Beaker A Boiling water Heat D pure water collected Water
13. 13. Distilling Muddy Water to get Clean Water Thermometer Cold water in Flask Condenser Cold water Muddy out water Heat Beaker
14. 14. Distilling Muddy Water to get Pure Water Label the above diagram and explain in detail what is happening to the muddy water to get pure water. N
15. 15. CHROMATOGRAPHY Some solids dissolved in a solvent can be separated by a method called Chromatography. Ink pens such as felt tips can often contain a number of different dyes. With many coloured inks water can be used as a solvent to separate these dyes. In this way inks ( and other mixtures) can be tested to see if they are pure or made up from a number of different dyes mixed together.
16. 16. CHROMATOGRAPHY There are two reasons for the separation by chromatography, of the different chemicals in a mixture. 1. Some chemicals will dissolve in the solvent more quickly, the better they dissolve the further they travel. 2. The paper absorbs different chemicals to different extents.
17. 17. CHROMATOGRAPHY A spot of ink in the A dropper pipette is centre or some used to add drops of Chromatography water to the spot of paper ink The drops of water causes the dried ink spot to spread outwards. As the ink is made up from different colours that travel at different rates through the paper, the ink is separated into the different colours forming the cultured rings.
18. 18. CHROMATOGRAPHY A spot of ink in the A dropper pipette is centre or some used to add drops of Chromatography water to the spot of paper ink Explain what is happening to the dried ink spot in the second diagram. N
19. 19. CHROMATOGRAPHY Red Yellow Blue 1 2 3 4 Pure Inks Unknown Inks N
20. 20. SOLUBILITY If a substance dissolves it is said to be Soluble. How hard it is to dissolve it or how easy it is, is known as its’ Solubility. Solubility can be affected by different factors, one of which is the Temperature of the Solvent which is dissolving the Solute (the substance being dissolved).