Grade 5 · Unit 3: States of matter

Evaporation

Where does a puddle go when it dries up?

After the rain stops, puddles slowly dry up in the sun.

Puddles disappear

After rain, puddles slowly disappear. The water has not soaked away – much of it has turned into an invisible gas called water vapour. This change from liquid to gas is called evaporation.

Some of the water from a puddle also soaks into the ground, but on a hard road, evaporation does most of the work.

Escaping particles

Liquids are made of particles that are always moving. Some particles at the surface move fast enough to escape into the air. Evaporation happens at any temperature, not only when water boils.

Only the fastest particles at the surface escape. Warming the liquid gives more particles enough energy to escape, so it evaporates faster.

Evaporation everywhere

Wet clothes dry on a washing line. Wet hair dries after a bath. Water in a glass slowly goes down if you leave it for many days.

Evaporation is faster when it is warm, windy and dry. That is why clothes dry quickly on a sunny, breezy day in spring.

Evaporation cools

When you sweat, the sweat evaporates from your skin. Evaporation takes heat away, so it cools you down.

Dogs cool down by panting. Water evaporates from their tongues and mouths and carries heat away.

What I learnt