Hands on science

Science World, Oct, 1997

How many steps does it take to clean muddy water? Find out by trying this experiment.

WHAT YOU NEED

muddy water (mix 1 cup water and 2 tsp dirt) * funnel * coffee filters * sand * gravel * clear, plastic cup

WHAT TO DO

1. Place the filter in the funnel. Set the funnel on the plastic cup.

2. Pour the water through the filter. How well did the filter clean the muddy water?

3. Put a new filter in the funnel and add a layer of gravel in the bottom of the funnel. Then add a layer of sand.

4. Pour the water through the filter again. Is the water clearer?

CONCLUSION

How do sand and gravel help clean water?

DON'T STOP NOW!

Check out the miniposter on pages 12-13 to see how water-treatment plants work!