Interactive Primary Newsletter 21
Earth and Space     Changing materials
Describe how solids of different sizes can be separated		Level C
Model of a Filtration System This stage requires filtering through a bed of aggregate, mixed rock and stones. It is a simple system to model; all we need is a flour sieve, a 2-litre plastic drink bottle with the bottom cut out, a gauze bandage or similar material, fine gravel and small stones. If groundwater is taken from a muddy puddle or burn, first run it through the flour sieve to collect all large pieces, twigs etc. Collect the water in a bowl or basin then transfer to our homemade filter. Hopefully we should collect a fairly clear sample. If the water is still cloudy we could add 2 teaspoonfuls of potash alum (potassium aluminium sulphate - see secondary school for this). This should bring together particles in the water and allow them to settle to the bottom of the container. We now should have a reasonably clear sample. SAMPLE SHOULD BE FOR DEMONSTRATION PURPOSES ONLY. DO NOT DRINK Click the graphic below for the complete drawing of a treatment plant
Explain how evaporation and filtration can be used in the separation of solids from liquids		Level D