Project: Obtaining clean drinking water
In nature water is not always clean: mud, rubbish, factory and household waste water, chemicals and germs may enter it. Drinking untreated water leads to stomach and intestinal illnesses and other harm; toxins from polluted water can reach our bodies through fish and other organisms. Filtering means passing water through porous layers to separate small particles such as sand and mud. A simple filter model is made of layers: gauze, cotton wool, activated charcoal (it absorbs smell, colour and some substances) and cleaned sand. Important: such a filter removes only visible dirt and does not completely remove germs; therefore the filtered model water must NOT be drunk. For drinking, water is taken from a clean source and boiled (boiling at 100 °C kills germs) or put through special treatment.
Project: 1) an adult cuts the bottom off a plastic bottle and it is placed upside-down as a funnel (or use a funnel); 2) add layers: gauze, cotton wool, gauze, crushed activated charcoal (pharmacy tablets) and gauze, washed and dried sand, gauze again; fasten with a rubber band; 3) slowly pour “dirty water” over it (made by mixing soil and water in a container – not real river or ditch water); 4) collect the water that drips out in a glass and compare its clarity with the original. Safety: do NOT drink the filtered water; an adult cuts bottles and sharp items; only an adult heats and dries the sand; avoid breathing charcoal dust and wash hands.