10+
Gallery 8

Evaporation

The evaporation exhibit consists of a thermal camera, observing water vapour, and a monitor showing different colours of the results.
The evaporation exhibit consists of a thermal camera, observing water vapour, and a monitor showing different colours of the results.

Liquid water absorbs energy when it evaporates to form water vapour gas.

How it works

Watch water evaporate through a thermal camera and observe differences in temperature as the water changes state from liquid water to water vapour gas.

Things to try or ask around the exhibit

  • See if the thermal camera will detect a hand print left on the back board.
  • Which part is warm and which part is cool?
  • Where is the water gas?
  • When your skin perspires or sweats during Summer, where does the sweat go?

Background

When heating water, the temperature rises to a certain point, then the temperature 'plateaus' or remains constant as water absorbs enough energy to boil or change its physical state from liquid to gas. This temperature point represents water's latent heat, which is the heat energy absorbed by water as it changes state.

Water has a high latent heat, which means it absorbs a lot of heat energy before it boils or evaporates. One kilogram of water (about the size of a milk carton) at room temperature requires around 2200 kJ of latent heat energy to change from liquid water to gasesous water vapour.

Heat energy absorbed during evaporation loosens chemical bonds between water molecules, so the molecules break free and become gaseous water vapour molecules. While evaporation usually occurs through heating, evaporation rates can also increase due to wind speed and 'dryness' or lack of humidity in the air.

Finding the science in your world

When water evaporates, it absorbs energy, which can be helpful in cooling things down.

Humans perspire (or sweat) and dogs 'pant' to allow evaporation of moisture from their bodies, which absorbs body heat and cools down their body temperature.

Water's ability to absorb a lot of heat as it evaporates is sometimes used in the disposal of wastewater, but this process can use a lot of energy because of the large amount of water involved.