Filtration & Crystalisation

Question 1

What is the best method to obtain a sample of salt from a salt solution?

Answer 1

Evaporation

Filtration can only separate undissolved solids from a liquid, and fractional distillation is used to separate multiple liquids

Question 2

Describe how you would carry out the process of crystallisation.

Answer 2

First, pour the solution into an evaporating dish and heat it using a Bunsen burner.

Stop heating it when crystals start to form (‘point of crystallisation’) and allow it to cool down.

Then either leave it to allow the rest of the water to evaporate, or filter out the crystals using filter paper and a funnel. Lastly, dry the crystals in a warm oven.

Question 3

How would you separate pieces of rock from a solution of salt water?

Answer 3

Filtration

The rocks are solid and so can be captured by the filter paper, whereas the solution of salt water will pass straight through.