Water Thermometer - Sick Science!

Watch the temperature rise with this homemade thermometer

Is it possible to make a thermometer out of water? Absolutely! The best part about our Water Thermometer experiment is that you have all the materials you need in your own home. That's right, you'll be measuring temperature with this amazing homemade tool in no time.

Materials

Glass bottle
Straw
Modeling clay
Food coloring
Container of hot water
Container of cold water
Heavy glove

Experiment
Video
Reviews

Fill the glass bottle up to the bottom of its neck with cold water.
Add a few drops of food coloring to the water in the bottle. You pick the color!
Place a straw (make sure it's long enough) into the bottle. Pack clay around the straw and bottle neck. Make as tight of a seal as possible.
Now that you've made your thermometer, set the bottom of the bottle into the container of hot water. What happens to the water inside the bottle?
Make sure you are wearing a heavy glove and remove your water thermometer from the hot water.
Put the water thermometer into the container of cold water. What happens to the water inside the bottle this time?
Try experimenting with other water temperatures.

How does it work?

Water, like all substances, is comprised of molecules. In water, an individual molecule has the chemical formula H₂O, dihydrogen monoxide. When water molecules are heated, their bonds stretch out and expand. In the Water Thermometer experiment, you've created a sealed environment around the water. That is to say, there is nowhere for the water to go as it expands because the rest of the space is filled with air. The straw gives the expanding water an area where it can expand.

In comparison, the opposite happens when water is cooled. The molecular bonds that hold the H₂O molecules together contract, bringing the molecules closer together. Just as the water level in the straw rises when the water is heated, it lowers when the water is cooled.