A simple liquid thermometer is built using a straw, bottle, rubbing alcohol (or water), and food coloring to demonstrate how liquids expand and contract with temperature changes.

1. Use a permanent marker to mark a clear plastic drinking straw with one centimeter intervals from the bottom up.
2. Soften a small amount of modeling clay and flatten it into a round disk larger than the neck of a small bottle.
3. Poke a hole through the clay using the straw to make a snug fit for the straw.
4. Fill the bottle one-third to halfway with rubbing alcohol or water. Add a few drops of food coloring and shake gently to mix.
5. Insert the straw through the hole in the clay and place the clay over the bottle’s mouth, ensuring the straw dips into the liquid but does not touch the bottom.
6. Seal the neck of the bottle airtight using the clay, but keep the straw’s top open.
7. Use a dropper to add more alcohol or water into the straw until the colored liquid level is visible in the straw.
8. Mark the current liquid level as room temperature.
9. Place the bottle in a bowl of ice water and mark the new level when the liquid stops moving (this corresponds to 0°C/32°F).
10. Warm the bottle with your hands or place it in warm water to see the liquid rise, marking this higher level.
11. Use your homemade thermometer to compare temperatures in different locations around your home.

DIY: Build your own thermometer - WDIO:

Make a Thermometer - STEM Activity - Science Buddies:

📄 Measure Up with a Homemade Thermometer - Science Buddies: https://www.sciencebuddies.org/stem-activities/homemade-thermometer

• Build thermometers with straws of different diameters to compare accuracy.
• Calibrate your thermometer using a store-bought one to add a temperature scale.
• Use different colored liquids to make multiple thermometers for indoor and outdoor comparison.

• Work in a well-ventilated area when using rubbing alcohol.
• Keep rubbing alcohol away from open flames - it is flammable.
• Avoid ingesting or inhaling alcohol fumes.
• Clean up spills immediately and wash hands after handling.
• Dispose of used rubbing alcohol safely by flushing it down the sink with plenty of water.

• Why does the liquid rise when the thermometer is warmed? (The liquid expands as it heats up.)
• Why is it important to create an airtight seal around the straw? (It prevents air from escaping or entering, allowing accurate liquid movement.)
• What happens when the bottle is cooled? (The liquid contracts and moves down the straw.)
• Why is rubbing alcohol used instead of water? (It expands more uniformly and remains liquid over a wider temperature range.)
• How could you calibrate your homemade thermometer to measure actual temperatures? (By comparing the liquid levels to known reference points like ice water and warm water or using a commercial thermometer.)