What it shows
Gravel, sand and charcoal trap particles of different sizes, and charcoal also removes some colour and smell. The water looks clearer but is still not safe to drink, because germs pass through.
This idea has a short entry only. For the science behind it, read the sentence above with your textbook and ask your teacher to explain the law or idea it shows, so you can describe it in your own words.
Materials
- A plastic bottle cut in half
- Cotton wool
- Fine sand, coarse sand and gravel
- Activated charcoal
- Muddy water
Safety
For this project: Never drink the filtered water.
Never use mains electricity: power models with cells, batteries or a low-voltage adapter. Sharp and hot tools, flames and lab chemicals need an adult or your teacher beside you. Keep magnets, button cells and small parts away from young children, and wash your hands after making.
All the safety rulesHow to go about it
Numbered steps have not been written for this idea yet. Plan it with your teacher: sketch the design with measurements, build one part at a time, test each part, and write every observation with the date. The free ebooks below have step-by-step projects of the same kind.
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