You’ll need

  • 2 small plastic drink bottles (same size and shape)
  • Water at room temperature
  • Paper towels
  • An electric fan
  • A thermometer

What to do

  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 2 layers of paper towel and wet the paper towel with water.
  3. Stand the 2 bottles side by side in front of the fan. Let the fan blow on the bottles for 20 minutes.
  4. Take a sip of water from each bottle. Is the water still at room temperature? Is the water in one bottle cooler than in the other?
  5. Put the bottles back in front of the fan and check the temperature with the thermometer every 5 or 10 minutes.

Questions to ask

What happens if you leave the bottles in front of the fan?

How can you make the water cool even faster? Try turning the fan on a higher setting.

What happens if the paper towel dries out? Try using more layers of paper towels so they stay wet for longer.

What's happening

The water bottle wrapped in paper towel is cooled by evaporation. The term evaporative cooling is used for when temperature falls because of evaporation. Evaporation is the process where water turns from a liquid into a gas. Evaporation needs energy to do this. As each molecule of water evaporates from the paper towel, it takes some energy with it. It uses this energy to change from a liquid to a gas. Standing the bottle in front of the fan speeds up evaporation.

Transcript

Tim: Hi everyone, my name’s Tim and I'm from the Questacon Science Squad. Today I’m going to show you how to make a low budget drink cooler. To do that…

You need:

  • a plastic drink bottle filled with water
  • two sheets of kitchen paper and,
  • a container filled with water

So what you need to do is wrap the drink bottle in the layers of kitchen paper, dip that into the water and roll it around a few times, get it nice and wet and coat it in water, and then sit it down in front of a fan.

So you can switch your fan on and leave it there for about 20 minutes or so and then, once you have a look at it now, you can see it’s looking nice and chilly. Fantastic!

(Camera pans in on the bottle which is in front of the fan with mist coming out of it)

If you want to find out how this drink cooler works head to the Questacon Science Squad Website. See you next time.

Did you know

The only thing that stops Earth’s atmosphere filling up with water vapour is precipitation (this is things like rain, snow and hail). Rain and snow are always forming and falling to Earth’s surface. The energy absorbed during evaporation is released during precipitation. 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.