Science Experiment 8: Test the Temp

By AG Education 9 August 2016
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Are you cool? Are you hot? Today we’ll find out when we make our own thermometers!

National Science Week (Aug 13-21) is here again, and the team at Australian Geographic are really excited! We’ll be getting along to some of the events at the Australian Museum and Powerhouse, though there are events on all around the country.

To celebrate, we’re putting up a different science experiment every day! You can try these at school or at home, and they’ll help you learn more about space, volcanoes and heaps more. Have fun!

Building a Thermometer

Today we’ll build our own devices for measuring temperatures, using the principle that water expands when it is heated. Make sure you get an adult to help you with this one, you’ll need them for the first step!


  • A clean, empty screw-top container (like an old peanut butter jar)
  • A clear straw
  • Something to make a hole with, such as a nail or hand drill
  • Food colouring
  • Moulding clay or Play-Doh
  • Permanent Marker
  • Ice bath (ice cubes in a bucket)


  1. Get an adult to carefully bore a hold into the middle of the lid for your container, making sure it’s the same diameter of your straw, using the nail or hand drill.
  2. Fill your container to the brim with water
  3. Add a few drops of food colouring.
  4. Place the lid (with the straw in it) onto the container, and seal both the edge of the lid and the hole around the straw with your moulding clay. You want it to be airtight!
  5. Gently blow into the straw. This will increase the pressure inside the container. If your seals are airtight, water should creep up the straw when you stop blowing. This is a good test – if it doesn’t happen, work on your seals again!
  6. When the water creeps up as it should, mark that level with your pen. This is room temperature.
  7. Now you can test it out – trying warming the container with your hands or placing it in the ice bath. What happens to your water level?

This is the same principle that guides regular mercury thermometers. It expands rapidly when it’s heated and can be used to make extremely precise measurements.