Students build a simple water filter using a cut plastic bottle and layers of materials like sand, gravel, cotton, and activated charcoal. The experiment shows how filters remove impurities from dirty water, though the filtered water is not safe to drink.

1. Ask an adult to cut a clean 2-liter plastic bottle in half. Place the top half upside down into the bottom half to form a funnel.
2. Place a coffee filter, bandanna, or paper towel at the bottom of the funnel section.
3. Add filter materials (cotton, charcoal, gravel, sand, etc.) in distinct layers. Record the order of your layers.
4. Stir dirty water (mixed with soil, coffee grounds, leaves, or oil) and measure out one cup.
5. Pour the dirty water slowly into the filter while timing how long it takes to pass through. Record the result.
6. Observe how clear the filtered water looks. Scoop out each layer of filter material and note what impurities it trapped.
7. Rinse and repeat with different filter material orders to test how layering affects filtration.

Make a simple water filter experiment - SydneyWaterTV:

DIY water filter experiment - Aberdeen Science Centre:

📄 Make a water filter - National Geographic Kids: https://kids.nationalgeographic.com/books/article/water-wonders

📄 The Dirty Water Project: Design-Build-Test Your Own Water Filters - ncwit.org: https://www.teachengineering.org/activities/view/cub_environ_lesson06_activity2

• Test different filter materials such as paper towels, cotton cloth, or sponges.
• Compare coarse versus fine sand layers.
• Try different amounts of charcoal to see if it improves clarity.
• Time how long water takes to pass through short versus tall filter stacks.

• An adult should cut the bottle with a utility knife.
• Do not drink the filtered water—it may still contain harmful microorganisms and chemicals.
• Wash hands after handling dirty water.
• Dispose of filter materials properly.

• Why does water move more slowly through filters with finer materials? (Because smaller spaces between particles trap smaller impurities.)
• What role does activated charcoal play in the filter? (It attracts and traps tiny particles and chemicals using electrical charges.)
• Which order of materials made the cleanest water? Why?
• Why is the filtered water still unsafe to drink, even if it looks clear? (It may still contain bacteria, viruses, or dissolved chemicals.)
• How do natural water systems, like wetlands, act as filters in the environment? (They slow water flow and trap sediments, plants absorb pollutants, and microbes break down waste.)