methods of separating + purifying substances ×× filtration & crystallisation

Question 1

state some mixtures that can be separated by filtration

Answer 1

sand and water
dirt and water
cornflakes and milk
pebbles and water

Question 2

state some mixtures that can be separated by crystallisation

Answer 2

salt and water

Question 3

explain the formation of crystals during crystallisation

Answer 3

when a product is made as a solution, one way to separate it from the solvent is to make crystals. This involves evaporating the solution to a much smaller volume and then leaving it to cool. As the solution cools, crystals form, and these can be obtained by filtration.

Question 4

explain how mixtures are separated by filtration.

Answer 4

filtration is used to separate an insoluble solid from a liquid. It is useful for separating sand from a mixture of sand and water, or excess reactant from a reaction mixture.

filtration works because the filter paper has tiny holes or pores in it. These are large enough to let small molecules and dissolved ions through, but not the much larger particles of undissolved solid.