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Description

Similar to https://www.scouts.org.uk/activities/water-wash/ also available on OSM.

Resources

❏ 2 litres of stream or river water (or mix a handful of dirt into 2 litres of water)
❏ 2 empty clear 1-litre plastic soda bottles OR biodegradable paper cups (ideally different colours) to create multiple interchangeable levels of filtering.
❏ 30 cotton balls
❏ a thumb tack
❏ a stick or skewer
❏ 2cloth circles, about 6 inches in diameter, or round coffee filters (optional)
❏ A funnel
❏ 2 cups of cleaned activated carbon (charcoal) (this can be found in most pharmacies in the vitamin section)
❏ 2 cups of sand
❏ 1 cup of fired clay pieces (we crushed up inexpensive terracotta flower pots)
❏ Several empty 12oz cups to collect your filtered water (The bottle should be able to sit snugly in the top of the cups)

Instructions

1. Ask your scientist to create a testable question: Example: Does changing the arrangement of the layers affect how quickly the water is filtered?

2. Use the thumbtack to punch holes in the bottom of each soda bottle (1 per “bump” on the bottom of the bottle works well). OR if using paper cups, punch holes in the bottom of each cup that will become a filter layer.

3. Layer 10-15 cotton balls in the bottom of each bottle. Pull them slightly apart, then use the skewer or stick to smush them down into all of the bumps in the bottom of the bottle. The cotton needs to cover the entire bottom of the bottle to keep the sand from coming out. OR if using paper cups, create a single layer of cotton balls in one of the filter layer cups.

4. Optional: Use one cloth circle or coffee filter to cover the cotton balls. (Getting it in the bottle and then over the cotton can be tricky. You could ask an adult to cut the spout off your bottle so you have a larger opening to work with.) OR if using paper cups, cut a cloth circle or coffee filter to fit over the cotton balls in the filter layer cup.

5. Use the funnel to add a layer of sand (about 7cm or 21⁄2 inches deep is recommended). OR if using paper cups, in a new cup add a layer of sand to create a new single filter layer.

6. Then it’s up to your scientist! Experiment by adding additional layers. You could make one filter using the charcoal, make another one using the fired clay, or make one filter that uses both, or make one with just sand—experiment! OR if using paper cups, use one new cup to create each of your additional layers.

7. Place a collection pot or cup under your filter tower to catch the filtered water.

8. Place the small end of the funnel in the top of the bottle and pour about 1.5 cups of the dirty water into the top of your filter. OR if using paper cups, carefully pour water into the to cup filter layer. Wait several minutes for the water to filter through. The water should drip SLOWLY out of the bottom of the filter.

9. See how many times you need to pour the water through your filter(s) until it becomes clear. If indoors, make a chart to track which filter works best.

10. Filter the water enough times until it looks clean. DO NOT DRINK IT! (It may be that boiling the water for at least 1 minute COULD make it safe to drink, but we VERY STRONGLY DISCOURAGE drinking ANY water
from this experiment!)

Tags

• experiment
• water filter

Badge Links

• Adventure - Outdoor activity
• Experiment - Experiment
• Global Issues - Water filter
• Outdoors - Natural activity
• Skills - Problem solving
• Teamwork - Challenge