Water filter

Students build a filter using a bottle, sand, gravel, and charcoal to purify dirty water.

Steps

1. We cut a plastic bottle and invert the top part like a funnel.
2. We layer materials: cotton wool, activated carbon, sand, gravel.
3. We pour muddy water through and compare before and after.
4. Discussion: why can't this water be drunk right away?

Tip: You can buy activated carbon at an aquarium shop.

Materials needed

• Activated carbon (1 pack)
• Aquarium gravel (1 kg)