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Separating Mixtures Year 7 Science ACARA

The document outlines various methods of separating mixtures based on physical properties, including hand sorting, sieving, filtration, magnetic separation, evaporation, distillation, and chromatography. It explains that mixtures consist of at least two different substances and provides examples of common mixtures, such as air and sea water. Additionally, it defines key terms and the processes involved in each separation method, highlighting the importance of the physical properties of the materials.

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METHODS OF SEPARATING MIXTURES
Hand Sorting Using the physical properties of size, shape, texture colour. eg Sieving separation mixtures with a sieve, using the property of size eg Filtration separating mixtures with a filter, using the property of size Magnetic separation A magnet is useful for materials with magnetic properties. eg Evaporation separate a solution. Evaporation is the process of separating a liquid or solvent part (like water) into a gas (water vapour). When you evaporate salt water, the crystals of salt are left behind. Distillation Distillation is a method that combines boiling and condensation. It's for when we want to keep the solvent Chromatography a method of separating a solution of different colours. Black ink is an example of a mixture of colour pigments in water. Bonus: Centrifuge: we spin a suspension very fast. The heavier particles sink to the bottom and the lighter go to the top.
Topic :
What are we going to learn? • Methods of separating substances in a mixture (based on different physical properties) • Hand sorting • Sieving • Filtration • Using a magnet • Evaporation • Distillation • Chromatography
What we already know • A mixture consists of at least two different substances of material mixed together. • A solution is a mixture of a dissolved solid and a liquid. • When a gas cools and becomes a liquid, we call this change condensation.
New words • Sieving: separation mixtures with a sieve, using the property of size • Filtration: separating mixtures with a filter, using the property of size
Mixtures and methods of physical separation • Mixtures consist of at least two different substances or materials mixed together. • Some common examples of mixtures are air, sea water, concrete and brass. • Air is a mixture of gases – mainly nitrogen, oxygen and a little carbon dioxide. • Concrete is a mixture of lime, cement, sand, stone and water . • Brass is a mixture of copper and zinc.
Methods of physical separation •The physical properties of the materials in a mixture determine the separating method that you use. • Hand sorting: • Sieving
Methods of physical separation…cont •Filtration • Filtration is a method of separating mixture with particles of different sizes using a filter • The difference between a filter and a sieve is the size of the wholes • The holes in a filter are too small to see • A filter is normally made of paper, cloth or plastic • When you filter a mixture of a solid and a liquid, the liquid part goes through, and the solid part stays on the filter paper • Examples of mixtures that can • be separated by filtration are: • sand and water, coffee grounds • and water
Using a magnet • What if it is too slow or difficult or dangerous to sort a particular material by hand? • A magnet is useful for materials with magnetic properties. • The photograph shows a giant scrapyard magnet that is used to sort scrap metals.
Using a magnet…cont • Metals such as iron, steel and nickel are attracted to magnets. • Metals such as copper and aluminium are not • Non-metals such as plastic and glass are also not attracted to magnets. • Examples of other metals that can be sorted by magnets are: iron, filings of sand and iron nails from broken glass.
Evaporation • We’ve seen how to separate solids. • How do we separate a solution? • How do we get salt out of water? • We do it by evaporation. • Evaporation is the process of separating a liquid or solvent part (like water) into a gas (water vapour). • When you evaporate salt water, the crystals of salt are left behind. • This is called a solute.
Evaporation…cont • Sea salt is held in shallow evaporating pans or ponds. • The salt is collected once the water has evaporated.
Distillation • What if, instead of salt you want to get pure water from sea water? • You could do it by distillation. • Distillation is a method that combines boiling and condensation. • It separates substances with different boiling points. • The figure below shows the distillation apparatus. • The solution is heated so that the solvent (water) boils and becomes a gas (water vapour)
Distillation • The gas is collected in a long tube called a Liebig condenser • The jacket is cooled by a jacket of cold water, which cools down the gas. • The gas condenses back to a liquid (pure water) and it is collected in the flask • The solute (salt) is left behind.
Chromatography • Chromatography is a method of separating a solution of different colours. • Black ink is an example of a mixture of colour pigments in water. • Chromatography involves spotting of a mixture of colours onto filter paper. • The colour sticks to the paper and then spread out on the paper, carried by a solvent. • Some colours stick to the paper more strongly than other ‘s.
Chromatography • The more strongly the colour sticks, the slower and less further it travels. • The less strongly a colour sticks, the faster and further it travels.
Let’s revise 1. What does a mixture consist of? • Answer: At least two different substances of material mixed together •2. Explain what a solution is. • Answer: A mixture of a dissolved solid and a liquid •3. What happens when a gas cools? • Answer: It becomes a liquid, we call this change condensation •4. Explain the mixture of air. • Answer: It is a mixture of gases, mainly nitrogen, oxygen and a • little carbon dioxide. • •
Let’s revise • 5. Name the different method of separation. • Answer: hand sorting, sieving, using a magnet, evaporation, distillation chromatography • 6. When will you use hand sorting as a method of physical separation • Answer: When we sort plastic from paper • 7. Explain what filtration is • Answer: A method of separating a mixture with particles of different sizes using a filter • 8. Where and why will a magnet be used for sorting? • Answer: In a giant scrapyard when it is too slow or too dangerous to sort a particular material by hand
Let’s revise • 9. Explain what evaporation is? • Answer: It is the process of separating a liquid or solvent (like water) into a gas (water vapour). • 10.Explain what a solute is. • Answer: When we evaporate salt water, the crystals of salt that are left behind is called a solute. • 11. When will we use distillation as a method of separating mixtures? • Answer: When we want to get pure water from sea water.
Questions