Homemade Thermometer Experiment

This homemade thermometer science experiment is a cool demonstration to show kids how thermometers work and to talk about heat and temperatures. Liquid thermometers have been around for hundreds of years. While most of us now use digital thermometers to take a temperature, liquid ones are neat to study and learn about as well!

EXPERIMENT:

1. Pour equal amounts of water and rubbing alcohol into the bottle until it is 1/4 of the way full. Add in a few drops of red food coloring to make it more visible and to look like a thermometer.

2. Put the straw into the bottle and wrap the clay tightly around it and the opening of the bottle. You do not want the straw touching the bottom of the bottle, so move it up and have the clay hold it in place. Leave the top opening of the straw uncovered.

3. Now you can test the thermometer! Put your hands around it to see if that warms it up. You'll get a small reaction with the heat from your hands. Now try putting it into the freezer to see what change happens. Test it outside in your weather on a hot or cold day and see what happens.

CONCLUSIONS:

How and why does this homemade thermometer work? This is called thermal contraction and expansion. When the alcohol and water mixture gets hot, it expands. This increases the pressure inside the bottle and pushes down on the liquid in the jar. Since the clay has sealed it in, it has nowhere to go but up the straw! When it cools down again, the liquid will return back down the straw.