How to make your own Bottle Thermometer. Science is Awesome!

Active vs Passive Cooling
Material required for this project:
1. Glass Bottle
2. Clear Straw
3. Modelling Clay
4. Food Color
5. Water
Step 1: Mix the ingredients
Mix your water and food coloring and put them in a clean glass bottle. Fill the bottle just over halfway with water. (The food coloring is optional, but it will make your thermometer much easier to read.)
Step 2: Attach the straw
Insert the clear straw into the bottle and attach it using the modeling clay. Make sure the straw does not touch the bottom of the bottle and that the modeling clay is not covering the top of the straw.
Step 3: Test it out
Now you have a functioning thermometer! Time to test how it works. Mark on the straw where the water level currently is and then take the bottle outside into the direct sun. Does the water level rise?
Step 4: Find improvements
Run some tests to see if the thermometer will work better or worse with other liquids you have at home (e.g., juice or milk). Be sure to not use flammable liquids as you need to leave your thermometer in the sun!