The first thermometer was invented by Galileo around 1593, based on the premise that air expands due to heat and contracts due to cold. However, it was not until 1714 that Gabriel Fahrenheit invented the first reliable mercury thermometer that is still in use today. Creating a homemade thermometer is a fun way to get your kids involved with science. Just use a few household items and you will be measuring the atmospheric temperature in no time.
Fill the clear bottle ¼ of the way full with equal amounts of water and rubbing alcohol. Add food coloring and mix well.
Arrange the clay around the opening of the bottle and place the straw in the middle. Keep the straw from touching the bottom and close the opening with the clay. Ensure that no air can get into the bottle.
Test your thermometer by putting hot water in the cup. Place the bottle in the cup and watch as the liquid mixture rises through the straw, then decreases after the bottle is removed and cools off.
Cut two lines out of the middle of the index card to fit the straw through. Mark the card with lines representing the temperature at which the liquid expands or contracts. This will enable you to read your temperature.
To calibrate your thermometer, place it in water and get the temperature of that water with another thermometer. Mark that temperature on your paper indicating the temperature. Remove the thermometer and replace it in warm water, testing the temperature of the warmer water with another thermometer. Mark that temperature. Fill in the rest of the numbers for your thermometer to gauge the temperature.