Which Materials Keep Water Out? A Waterproof Design Challenge

What You'll Learn

• Absorbent material soaks water up (paper, cloth, sponge, cardboard).
• Waterproof isn't about thickness — a thin plastic sheet beats a thick paper
• Engineers choose materials for the job: roofs, raincoats, and umbrellas all
• A fair test drips the SAME number of drops on the SAME-size piece of each

Words to Know

Waterproof

Keeps water out — drops bead up and roll off.

The plastic sheet was waterproof — the house stayed dry.

Absorbent

Soaks water up like a sponge.

The paper towel absorbed every drop.

Bead up

When water forms little balls on a surface instead of soaking in.

The drops beaded up on the plastic and rolled away.

Soak through

When water goes all the way into a material.

The paper roof soaked through and dripped inside.

Material

The stuff something is made of — paper, plastic, cloth, metal.

Engineers pick the right material for the job.

Check What You Learned

Fun Facts

• Waterproof materials don't absorb water — drops bead up and roll off their surface

  Source: NGSS 2-PS1-2 — material properties tested for a purpose; TEKS 3.6D

• Absorbent materials soak water up — paper, cloth, sponge, and cardboard pull water into their fibers

  Source: standard absorbent/waterproof material properties

• Plastic, wax, rubber, and metal are waterproof — water beads on them

  Source: material property tables for elementary science

• Waterproofness is a property of the material itself, not its thickness — a thick paper towel still soaks through; a thin plastic sheet stays dry

  Source: NGSS 2-PS1-2 property-based selection

• Ducks' feathers are waterproof because of a waxy oil coating that makes water bead off — keeping them dry and buoyant

  Source: standard animal-adaptation science; TEKS animal-structures curriculum

• A fair drip test uses the same-size pieces and the same number of drops on each material

  Source: NGSS 3-5-ETS1-3 controlled tests