This super fun weather experiment will help any kid become a meteorologist by making their own thermometer that measures the temperature! Let’s get started with this bottle thermometer experiment!
Get more fun and educational Experiments With Rubbing Alcohol here!
Kids will love watching the fluid inside their thermometer rise as the temperature climbs, and drop as the temperature falls!
Bottle Thermometer Experiment
- Narrow Neck Glass Bottle
- Modeling Clay
- Rubbing Alcohol
- Food Coloring
- Bowl of hot water
- Bowl of ice water
How To Make A Bottle Thermometer
- Fill a bottle about 1/3 of the way with water.
- Pour some rubbing alcohol into the bottle.
- Add food coloring and mix it up.
- Put a straw into the bottle and secure it at the top with modeling clay.
- Set the bottle in a bowl of hot water and watch the water level rise in the straw.
- Plate the bottle in cold water and watch the water level drop in the straw.
Step 1: Fill A Bottle 1/3 Full With Water
Finding the right type of bottle is sometimes the hardest part of doing this experiment.
You need a narrow neck glass bottle that is clear to allow you to see the fluid rising in the straw inside.
Coca-Cola and other soft drink companies do make some glass bottles that work great for this bottle thermometer experiment.
Once you find a bottle that will work, make sure it is clean and empty, and then fill it about one third of the way with some water.
Step 2: Pour Some Rubbing Alcohol Into The Bottle
Now add about the same amount of rubbing alcohol into the bottle as you did water.
This should bring the half water and half rubbing alcohol mixture to about two thirds of the way to the top of the bottle.
Note: You can do this with just water, but the rubbing alcohol lowers the freezing temperature of the fluid.
This will help keep the thermometer working in colder temperatures!
Step 3: Add Food Coloring And Mix It Up
Put a few drops of red food coloring into the bottle and shake it up and little bit.
The food coloring will make the fluid inside the bottle look more realistic and give the appearance of mercury used in a real thermometer.
Step 4: Secure A Straw In The Opening
Now grab a clear plastic straw and stick it into the top opening of the bottle.
Keep the straw from falling all the way into the bottle while securing the straw to the opening of the bottle with some modeling clay.
Leave 2 or 3 inches of the straw poking out of the top of the bottle with the bottom of the straw below the fluid level.
Just make sure the bottom of the straw is not touching the bottom of the bottle.
Double-check the modeling clay at the top of the bottle to make sure it is sealed airtight around the straw. It won’t work if there are any leaks.
Step 5: Set The Bottle In Hot Water
It’s time to put our homemade thermometer to the test in some hot water!
With the help of an adult, fill a large bowl with some very very hot water!
The hotter you can get the water the better this will work, but be very careful not to burn anybody!
Now gently set the bottle thermometer into the bowl of hot water and watch as the red fluid inside slowly rises higher and higher in the straw!
It will take a few minutes for the water to get to its highest point, but it will continue to rise until the water inside the bottle has warmed up to the temperature of the water in the bowl.
Step 6: Set The Bottle In Cold Water
Once the red fluid has almost reached the top of the straw, gently move the bottle thermometer from the hot water bowl to the cold water bowl.
Again, you want the cold water to be as icy and cold as possible to make the fluid drop faster in the thermometer.
Within a couple minutes the red fluid in the bottle thermometer will start to drop!
When the fluid inside the bottle has cooled to the same temperature as the cold water in the bowl, the fluid in the straw will be level with the fluid in the bottle again.
Homemade Thermometer Explanation
The science behind how this bottle thermometer experiment works is very similar to our Hot and Cold Balloon Experiment we did too!
Our homemade thermometer works in the same way that a real thermometer does to tell us the temperature!
As the water and rubbing alcohol mixture heats up, it expands and pushes the red fluid up into the straw.
When the water and rubbing alcohol cools down, the molecules contract and the fluid in the straw begins to drop.
Real-life thermometers typically use mercury or alcohol as the rising and falling fluid inside because they have a much lower freezing point than water!
PIN THIS EXPERIMENT FOR LATER