Topic
Separation techniques

Timing
45 minutes

Description
In this experiment students use simple processes to separate sand and salt.

Apparatus and equipment (per group)

1. 250 cm(3) Beaker
2. Filter funnel and paper
3. Evaporating dish
4. Tripod
5. Bunsen burner
6. Gauze
7. Glass rod for stirring

Chemicals (per group)
A mixture of salt and sand (about 20 percent of salt)

Teaching tips
It can be effective to show the separate sand and salt to the whole class. Mix them at the front of the class, then use this as an introduction to a class discussion about how to separate them.

Background theory
The principles of filtration, evaporation, and the dissolving process.

Answers

To dissolve the salt in water.
The sand is filtered out into the filter paper; the filtrate is salt solution.
To remove the majority of the water.

Introduction
In this experiment simple processes are used to separate salt from a sand and salt mixture.

What to do

1. Mix about 5g of the mixture with 50 cm(3) of water in a 250 cm(3) beaker. Stir gently.
2. Filter the mixture into a conical flask and pour the filtrate into an evaporating basin.
3. Heat the salt solution gently until it starts to ’split’. Care: do not get too close.
4. Turn off the Bunsen burner and let the damp salt dry.

Safety
Wear eye protection.

Questions
Why is the salt, sand and water mixture stirred in step 1?
What happens when this mixture is filtered in the step 2?
Why is the salt heated in step 3?