Explanation:

This is a very straightforward experiment. It can be CARRIED out individually or in groups of two. Pupils must stand up during heating activities and beware of hot salt spitting when evaporation is almost complete.

Equipment

Apparatus

Eye protection

Beaker, 250 cm3

Glass stirring rod

Filter funnel

Filter paper

Conical flask, 250 cm3

Evaporating basin

Bunsen burner

Heat resistant mat

Tripod

Gauze

Chemicals

Mixture of sand and sodium chloride (salt), about 6–7 g per GROUP of students (a suitable sand–salt mixture should contain approximately 20% salt by mass)

Health, safety and TECHNICAL notes

Wear eye protection THROUGHOUT this experiment.

Pupils must stand up during heating activities and beware of hot salt spitting when evaporation is almost complete.

Sodium chloride (eg table salt), NaCl(s) - see CLEAPSS Hazcard HC047b.

Procedure

Pour the sand–salt mixture into the beaker so that it just covers the base.

Add about 50 cm3 of water, or add water until the beaker is about one-fifth full.

Stir the mixture gently for a few minutes.

Filter the mixture into a conical flask.

Pour the filtrate into an evaporating basin.

Heat the salt solution gently until it STARTS to decrepitate (spit). CARE: Keep eye protection on and do not get too close.

Turn off the Bunsen burner and let the damp salt dry in the dish.