Chapter 1.3 How Substances In Mixtures Are Separated

Question 1

Describe how sieving can be used

Answer 1

When … is sieved, … falls through the holes in the sieve, leaving lumps of … behind
It can be used to separate solids with different particle sizes

Question 2

Crystallisation steps (pure copper (II) sulfate) crystals

Answer 2

1. Heat the solution until its saturated
2. Cool saturated solution until crystals form
3. Filter and collect the solid crystals. Wash crystals with a little cold distilled water to remove impurities
4. Dry crystals between a few sheets of filter paper

Question 3

Describe the steps of using separating funnel

Answer 3

Pour the mixture into the separating funnel and leave it to settle into separate layers
Each component can be removed by opening tap at bottom and collecting in separate flasks/beakers

Question 4

What is the Rf value

Answer 4

Retention/retardation factor

Distance travelled by substance over distance travelled by the solvent

(Ratio of the two distances, no units)

Question 5

Describe steps to separate salt and sand mixture using filtration and evaporation to dryness

Answer 5

1. Add pure distilled water to the mixture. Stir to dissolve the table salt. Sand is insoluble in water
2. Filter the mixture. Sand is the residue, salt solution is the filtrate. Wash the residue with some distilled water. Dry sand between sheets of filter paper.
3. Evaporate salt solution to dryness. Salt will be left behind

Question 6

Sublimation

Answer 6

used to separate substance that changes from solid to gaseous state directly