Traditional thermometers measure temperature using mercury, but you can make your own at home with just water and rubbing alcohol. While a home thermometer cannot determine if you have a fever, you can still find out how hot or cold the environment is in your home. With just a few household supplies, you can do a fun science experiment that can help you measure temperature!
Part 1 of 2: Assembling the Thermometer
Step 1. Mix 2 ½ oz (75 ml) of cold water with 2 ½ oz (75 ml) of isopropyl alcohol
Use a measuring cup to mix equal parts of tap water with rubbing alcohol. You can mix the solution in the measuring cup or pour it directly into a 600 ml (20 oz) plastic water bottle.
- You can buy rubbing alcohol at your local pharmacy.
- Do not drink the mixture once you have prepared it, as its consumption is not safe.
Step 2. Add a few drops of red food coloring to the solution if you want it to look better
The food coloring makes the water look like the mercury used in traditional thermometers. Pour a drop or two into the solution and stir until mixed.
This step is optional if you don't have food coloring
Step 3. Place a straw in the bottle so that it does not touch the base
Use a straight, clear straw so you can see the liquid inside. Insert it through the opening of the bottle and hold it so that it is submerged, but remains just above the base.
If the straw touches the bottom of the bottle, the solution will not be able to travel through the bottle and the thermometer will not work
Step 4. Wrap playdough around the top of the straw to seal the bottle
Shape the play dough over the opening of the bottle to give it a tight seal. Make sure the straw isn't collapsed or clogged at the top as you apply the playdough, or the thermometer won't work. Once you finish applying it around, the thermometer is complete.
- You can buy playdough at craft or craft stores.
- As an alternative method, you can drill a hole in the top of the bottle that is large enough in diameter so that you can insert the straw and seal the edges with a little clay.
Part 2 of 2: Measure temperatures
Step 1. Label the water level at room temperature
Observe the level of the liquid inside the straw and use a permanent marker to draw a line on the bottle. Take a measurement using a mercury thermometer on a table to find the actual temperature of the room. Write it next to the line on the bottle.
Step 2. Place the bottle in a bowl of hot water and label it
Fill the base of a container large enough to cover the thermometer with warm water. Put the thermometer in the container and watch the water level rise inside the straw. Once it stops at a certain level, draw a line on the bottle or straw using a marker and label it with the actual temperature of the water.
- Heat causes the solution to expand. Since the bottle is airtight and can only expand through the straw, the water level will rise inside it as it expands.
- If the water is too hot, it could come out of the top of the straw.
Step 3. Test the thermometer in cold water and mark the bottle with the respective temperature
Put the bottle in a different container of cold water. Notice how the water level in the straw drops as it spends more time in the cold water. Once this level has stabilized, label the listed temperature.
- The alcohol and water solution condenses as it cools, causing the level to drop inside the straw.
- The mixture inside the thermometer will freeze if it falls below 0 ° C (32 ° F) and it will not work.
Take the thermometer to various places to see where the temperatures vary
- Do not drink the solution from inside the thermometer.
- Avoid squeezing the bottle, as the liquid will gush out and stain the surroundings.