Which Material Keeps the Rain Out? A Waterproof Test for Young Scientists

Kids know that umbrellas and raincoats keep us dry. This test turns that knowledge into a fair test they can run in a corner of the classroom.

What you need

Cups, one per material
Squares of cloth, paper, foil, plastic wrap or a plastic bag, and cardboard, all cut the same size
Elastic bands to hold each square over a cup
A dropper or spoon, and water
Paper towel to put under each cup

The method

Predict. Which will keep the water out? Children can sort the materials into “will keep it out” and “won’t.”
Stretch each square over a cup and fasten with an elastic band.
Drip ten drops of water on the top of each material.
Wait a minute. Lift each square and look underneath, or look inside the cup. Is there water? Is the material wet right through?
Record with a tick or a cross in a chart.

Keep fair: same number of drops, same height, same waiting time.

What usually happens

Foil and plastic keep the water out.
Paper and cardboard soak up water and may go soft and let it through.
Cloth depends on the weave: some soaks through and some beads up.

Results differ with the materials you use, so go by what you see.

Talk about it

Which material kept the water out best?
Why do you think foil kept the water out and paper didn’t?
Which would you choose for an umbrella? A towel? Why not use the same for both?

The big idea

Materials have properties: waterproof, absorbent, stretchy, strong. We choose a material based on the job. A towel should soak up water. A raincoat shouldn’t.

Extend

Test a wet cloth inside a plastic bag and discuss.
Make a roof for a toy house and test it.
Compare light and dark materials in the sun, a different property.

The full lesson is Which material keeps the rain out? in Test It, Choose It: Materials. Sign up for three lessons free.