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Separating Substances D. Crowley, 2007 Thursday, July 6, 2017 Separating Substances • To know how to separate substances Key Terms • Name the following: - Solute Solvent Solution Solution - the mixture formed when a substance dissolves in it Solute - the substance that dissolves Solvent - the liquid in the solution Dissolve - mixing of a substance in a liquid Soluble - a substance which can dissolve (mix in a liquid) Insoluble - a substance which cannot dissolve (mix in a liquid) Accident • Transport company set to lose millions… • Yesterday a large truck crashed on the Marchwood Bypass shedding its load in the road – a representative from the transport company commented ‘this is a catastrophe! The truck was carrying a large amount of sand, salt and iron, all destined for different companies… • We do not know how we are going to fulfil these orders unless we are able to separate the mixture – if we fail to do this, we will lose an enormous amount of money!’ Accident • How could you help the company separate the sand, salt and iron – consider this in your groups… Filtration • How does filtration work? • Can you and your partner come up with a good explanation? • Filtration can separate in insoluble solid (does not dissolve) from a liquid What if its dissolved? • Some solids dissolve in liquids (soluble) – others, such as sand, are not (insoluble) • What could we do to separate something which has dissolved - e.g. salt from water? • Say we were stuck on a ship, out at sea, and we ran out of water - how could we get some fresh drinking water? Dissolved • • Why can’t we use filtration for salt and water? Think about the particles, and what happens to them when they dissolve • The salt has dissolved - its particles are thoroughly mixed, so they will just pass straight through our filter paper… • • Think about the Dead Sea - remember this has a very high salt level Rivers flow into it, but none flow out - the salt level increases, but the water level stays pretty constant - so where is the water going, and by what means?! Evaporation • The Dead Sea is so salty because no rivers flow out of it. This means, that when the water evaporates, the salt is left behind • Evaporation can be really useful - remember its where a liquid changes into a gas • Water can be evaporated, leaving our solute behind (the salt) Risks • Before you complete this experiment, we need to consider the risks • Using your risk assessment, think about the apparatus we are going to be using, and write in the risks and action to be taken… What will you do? • Tick which equipment you will need • Explain how you are going to carry out your experiment - how you will separate the sand, salt, iron and water? • And finally, draw the equipment you are going to use for the corresponding experiment Experiment • Remember all the safety rules we follow during an experiment… • Be as accurate as possible! • The group with most sand + salt + iron separated will be the winners Salt pile Sand pile Iron pile Review • How did the filtration separate the sand and water? • How did the evaporation separate the salt and water? • Why would filtration not separate salt from water? • Why did the magnet remove the iron but not the salt or sand? Filtration • Filtration works because the filter paper will stop the insoluble solid from passing through it - this makes it nice and easy for us to collect! The filter paper can easily catch the insoluble sand Evaporation • Evaporation helps us separate because some water particles are given enough energy to escape the attraction of the other particles. If we heat the water for a long enough, eventually all our particles are given enough energy to escape, just leaving salt • Salt cannot be separated using filtration, because the particles are too well mixed - this means that they would pass straight through the filter paper The filter paper cannot catch the soluble salt, as the particles are too well mixed Magnetism • Only some metals are magnetic, allowing this method to separate our iron from the other substances… Levels • Level 4 – the student draws a diagram and simply explains what has happened • Level 5 – the student draws a diagram using the correct symbols and explains filtration and evaporation using the correct scientific terms • Level 6 – the student draws and labels a diagram using the correct symbols and using a ruler and pencil. The student also explains filtration and evaporation using a particle model