Make and test a thermometer
How's the weather where you are? Let's start by finding out the temperature with a homemade thermometer. You'll need rubbing alcohol, clay and straws for this cool project! Or should we say...hot project?
Instructions
Step 1
Gather all your materials on a clean table so everything is within reach.
Step 2
Pour 1/4 cup of water into the cup or jar using the measuring cup.
Step 3
Pour 1/4 cup of rubbing alcohol into the cup or jar using the measuring cup.
Step 4
Add 5 drops of food coloring into the liquid to make it easy to see.
Step 5
Gently swirl the cup one time to mix the water alcohol and food coloring together.
Step 6
Place the clear straw into the cup so the bottom of the straw is near the bottom of the cup.
Step 7
Press modeling clay around the straw at the top of the cup to make an airtight seal.
Step 8
Blow gently into the straw one time to push some of the colored liquid up into the straw and create a starting column.
Step 9
Let the liquid settle then draw a starting mark on your paper at the same height as the colored liquid in the straw.
Step 10
With adult help place the cup into a bowl of warm water so the sides are surrounded and wait 30 seconds.
Step 11
Observe the straw and write down what happens to the liquid level during the warm test.
Step 12
With adult help place the cup into a bowl of ice water so the sides are surrounded and wait 30 seconds.
Step 13
Observe the straw and write down what happens to the liquid level during the cold test.
Step 14
Share a photo and your observations of your finished thermometer on DIY.org
Final steps
You're almost there! Complete all the steps, bring your creation to life, post it, and conquer the challenge!
Help!?
What can we use if we can't find rubbing alcohol, a clear straw, or modeling clay?
You can substitute rubbing alcohol with clear isopropyl alcohol (70%) or a liquid ethanol hand sanitizer, use a clean clear plastic pipette or glass stirring rod instead of the straw, and replace modeling clay with play-dough or silicone putty as long as it makes an airtight seal at the cup rim.
The colored liquid never rises in the straw — what might be wrong and how do we fix it?
Make sure the modeling clay formed an airtight seal around the straw, that the straw bottom is near the bottom of the cup (not blocked), and blow only one gentle puff as in step 7 so a stable starting column forms before you draw your starting mark.
How can we adapt this thermometer activity for younger or older kids?
For younger children, have an adult do the measuring, pouring of the 1/4 cups, clay sealing, and the one gentle blow while the child watches and makes the starting mark, and for older kids add a calibrated scale to the paper, record timed temperature changes in the warm and ice water tests, and compare results to a real thermometer.
What are simple ways to improve or personalize our homemade thermometer?
To enhance it, tape the labeled paper to the jar, calibrate the colored column against a real thermometer to mark degrees, decorate the jar, and then follow step 13 to photograph and share your finished thermometer on DIY.org.
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How to Make a Bottle Thermometer | Full-Time Kid | PBS Parents
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Fun Facts
❄️ Isopropyl (rubbing) alcohol has a much lower freezing point than water, so an alcohol thermometer won’t freeze as easily.
🎨 A tiny drop of food coloring makes the liquid column in a straw easy to see — that’s why homemade thermometers use color!
🧪 Alcohol expands more than water for the same temperature change, which makes alcohol-based thermometers very sensitive.
🌡️ The first thermoscope (a forerunner to the thermometer) was built by Galileo in the early 1600s to show temperature changes.
🔬 Thermometers work because liquids change volume with temperature — even a 1°C change can move the liquid a noticeable amount in a thin tube.
How do I make and test a homemade thermometer step by step?
What materials do I need to make a simple thermometer?
What ages is this homemade thermometer activity suitable for?
What safety tips and learning benefits should I know?
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