Separation techniques

Question 1

How does magnetic attraction work?

Answer 1

We use a magnet to separate the magnetic metals from the non-magnetic ones.

Question 2

What is magnetic attraction used for?

Answer 2

In scrapyards to separate the ferrous (iron-containing) materials from the non-magnetic ones so that they can be recycled.

Question 3

Name a few magnetic metals

Answer 3

Cobalt, nickel, iron, steel (contains iron)

Question 4

What do you need for a filtration set-up?

Answer 4

Filter paper, filter funnel, beaker.

Question 5

How does filtration work?

Answer 5

The liquid particles in a mixture are small enough to pass through the pores of the filter paper while the solid particles are too large to do so. Hence insoluble solid particles (residue) are separated from a liquid (filtrate).

Question 6

What are two applications of filtration?

Answer 6

• Separate tea leaves from tea using a tea strainer
• Filtration of groundwater in a situation pond

Question 7

What do you need for an evaporation to dryness set-up?

Answer 7

Tripod stand, evaporating dish, heat.

Question 8

How does evaporation to dryness work?

Answer 8

Solvent in the mixture changes from liquid to gas at a much lower temperature than the solute. Hence the solvent is removed, leaving behind the solute.

Question 9

What is evaporation to dryness used for?

Answer 9

To obtain a dissolved solid from a solution by heating it until all the solvent has boiled off.

Question 10

Two limitations of evaporation to dryness

Answer 10

• The solid obtained may not be pure as there may be soluble impurities left with the solid.
• Can only be used for solids that don’t decompose while heating, e.g. salt.