How to make a homemade thermometer

Thermometers are some of the most widely used instruments in the world, as they are able to measure the temperature of the environment or of a substance or material with which we are working, and for example together with the rain gauge or the anemometer they are the essential part of professional weather stations. Today, we will look at how to make a homemade thermometer quickly. If you don't want to complicate things, you can always buy one already assembled.

mercury thermometer


- A medium-sized (half-litre) bottle, preferably plastic.

- Isopropyl alcohol.

- A soda straw.

- Plasticine.

- Water.

homemade thermometer

Setting up our thermometer

To begin with, we clean the outside and inside of the plastic bottle with dishwasher, rinse well and let it dry. Once the bottle is dry, fill it with water until only a quarter of the bottle is free.

We then add about a quarter of a alcoholWe wait for the liquids to settle and then place the straw inside the bottle, preventing it from sinking to the bottom.

With the help of the plasticine, we fix the straw to the bottle to avoid alcohol leaks into the environment, and our homemade thermometer is ready. Now, we will carry out tests to verify its functioning.

Verifying operation

To check the functioning of the thermometer, we will place it in a warm place, such as the kitchen of our house, and check how the liquid moves inside the straw.

We mark with a pencil and repeat the test in a cooler or colder place, measure again and see how the behaviour of the liquid inside the straw changes.

homemade thermometer

How it works

The way it works is quite simple, the mixture of 75% water and 25% alcohol is quite sensitive to water. When we bring the bottle close to an environment where the temperature is high, heat is transferred into the bottle by conduction and the molecular motion causes the liquid to rise up the small plastic tube (straw), allowing us to take a temperature measurement.

The reverse process occurs in cold environments. If we perform several experiments with known standard temperatures, we can create a scale and have a very functional home thermometer.

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