C1, P1 Filtration and Crystallidation

What can physical separation techniques separate?

Mixtures, not the elements chemically joined in compounds.

What is filtration used to separate?

An insoluble solid from a liquid.

What does insoluble mean?

A substance that does not dissolve in a particular liquid.

What are state symbols, and where are they written? Give examples.

State symbols show a substance's physical state. They are written in brackets after a chemical formula: (s) = solid, e.g. AgCl(s); (l) = liquid, e.g. H₂O(l); (g) = gas; (aq) = dissolved in water, e.g. NaCl(aq).

What do (s), (l) and (aq) mean?

(s) solid; (l) liquid; (aq) dissolved in water.

What is an aqueous solution?

A solution in which a substance is dissolved in water.

What is crystallisation used to separate?

A soluble solid from a liquid.

Describe the method for separating an insoluble solid from a liquid by filtration.

1. Place filter paper inside a filter funnel. 2. Place the funnel over a conical flask. 3. Pour the mixture into the funnel. 4. The liquid passes through as the filtrate, while the insoluble solid remains on the filter paper as the residue.

What happens to the liquid during filtration?

It passes through the tiny pores in the filter paper.

What is the filtrate?

The liquid that passes through the filter paper.

Why does an insoluble solid remain in the filter paper?

Its particles cannot pass through the filter paper's pores.Its particles cannot pass through the filter paper's pores.

How can sodium chloride be separated from its solution by crystallisation?

Heat the solution gently to evaporate some of the water, then leave it to cool so crystals form. It can be done without heating- AQA method include Bunsen burner i think.

Why might it be better to let a solution evaporate without heating?

Some chemicals decompose (break down) when heated, so allowing the water to evaporate naturally helps prevent the solid from breaking down.

How can crystallisation be made faster?

Gently heat the solution to evaporate water faster.

During filtration, which substance is the residue and which is the filtrate? (2 marks)

Residue: the solid trapped by the filter paper (1). Filtrate: the liquid passing through (1).

Describe the method of crystallisation.

1. Gently heat the solution to evaporate the water. 2. As the water evaporates, crystals of the dissolved solid are left behind.