Toilet Roll Cooler

Be refreshed by the cool power of evaporation! Create your own refrigerator and cool your drink like a canvas water cooler bag.

Australian Curriculum links

  • Science > Physical Sciences > Year 3 > ACSSU049

You'll need

  • 2 small plastic drink bottles (same size and shape)
  • paper towel
  • water
  • thermometer
  • electric fan (or a windy day)

Try this

  1. Fill each drink bottle with water to the same level (the water should be close to room temperature).
  2. Wrap one of the bottles in two layers of paper towel and wet the paper towel with water.
  3. Stand the two bottles side by side in front of the fan and let the fan blow on the bottles for twenty minutes.
  4. Take a sip of water from each bottle. Has the temperature changed?
  5. Leave the bottles in front of the fan and check the temperature every five or ten minutes.

What's happening?

The water bottle wrapped in paper towel is cooled by evaporation. For evaporation to occur, water needs enough energy to turn from a liquid into a gas. As each molecule of water evaporates from the paper towel, it removes some heat from its surroundings, using this energy to escape into the air. Standing the bottle in front of the fan speeds up the process of evaporation.

Real world links

The only thing that stops the earth’s atmosphere filling up with water vapour is precipitation, which is caused by gravity. Somewhere rain and snow are continually forming as clouds and falling to the Earth’s surface. The heat absorbed during evaporation is released again during precipitation and this source of heat helps drive clouds and other weather systems. For example, evaporation from the ocean surface is the main source of energy for cyclones.

Sweating is your body’s way of using evaporative cooling to maintain a constant temperature.