Today in the BAASE we are going to make a homemade thermometer? It is a simple science experiment to try at home or in a classroom with children. You only need a few supplies.
- Modeling clay
- Red food coloring (optional)
- Clear straw
- Rubbing alcohol
- Small clear bottle with a narrow neck
- Thermometer (optional)
This homemade thermometer science experiment is a fun demonstration to show children how thermometers work and to talk about heat and temperatures.
Liquid thermometers have been around for hundreds of years. You can have your children research the history of liquid thermometers as a history project, that compliments this science project. While most of us now use digital thermometers to take a temperature, liquid ones are interesting to study and learn about as well!
HOW TO MAKE A HOMEMADE THERMOMETER
- 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.
- 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.
- Now you can test the thermometer! Put your hands around it to see if that warms it up. You get a small reaction with the heat from your hands.
- Place the thermometer into a bowl of really hot water to get a fast reaction. You can see when we put it into hot water, the liquid in the bottle rose above the clay.
- 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.
THE SCIENCE BEHIND THE HOMEMADE THERMOMETER
Want to know how and why this homemade thermometer works? 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.
How hot would it have to be for the water to come out of the straw?
Try to make a scale for the thermometer. Use a store bought thermometer to identify the temperature that the area where the homemade thermometer mixture is. Put a line on the straw where the liquid is, and mark the temperature that the thermometer says. Do this in various cold and hot places.