Unlock the Mystery of Hot & Cold: Craft Your Own Temperature Tracker

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Did you know that you can make your own working thermometer using a few supplies and some cool (pun intended) science?

The Temperature Tracker experiment helps children understand how temperature relates to feeling cold or hot while experimenting with thermal expansion. When the liquid mixture heats up, it expands!

Let’s get started!

How to make the Temperature Tracker experiment

Supplies you will need

For this experiment, you’ll need:

Supplies needed for the Temperature Tracker experiment

Before you start

Please watch your child around the rubbing alcohol.


Here is how to do this experiment with your child:

Step 1: Make the water/alcohol mixture

Pour equal parts of water and rubbing alcohol into the bottle, filling it about 2/3 to 3/4 full. Add a few drops of food coloring and mix gently.

Liquid mixture with food coloring in the glass bottle

Step 2: Insert the straw

Push the straw into the bottle, ensuring it reaches the liquid but doesn’t touch the bottom. Secure the straw tightly with modeling clay or Play-Doh around the bottle opening. You will want to make it as air-tight as possible.

It’s okay if some of the liquid mixture starts making its way up the straw as you secure the Play-Doh. It will self-regulate and go back down.

Inserting straw
Securing the straw and creating an air-tight seal with the Play-Doh

Step 3: Take readings!

Place your thermometer outside and take occasional readings. If you have a thermometer (even on your phone), you can use that to mark your bottle.

If you don’t have extreme temperatures outside right now and it seems pretty close to room temperature, then no worries! You can place your thermometer in an ice bath or a bowl of warm water to see how the liquid goes up or down (just be sure not to go from one extreme temperature to the next quickly; it may break your bottle).

Now, observe the liquid level in the straw as you expose the bottle to different temperatures:

  • Warmer temperatures: When you hold the bottle in your hands, the heat transfers to the liquid inside. The rubbing alcohol expands more than the water due to its lower thermal conductivity. This expansion pushes the liquid level up the straw.
  • Colder temperatures: Place the bottle in a bowl of ice water. The liquid will cool down, causing the alcohol to contract and the level in the straw to decrease.
Temperature Tracker in warm water, with liquid expanding up the straw

The science behind the Temperature Tracker experiment

This experiment teaches:

  • The science of temperature
  • Thermal expansion and contraction
  • Observation skills

How it works

The key to this experiment is the difference in thermal expansion between water and rubbing alcohol. Alcohol expands and contracts more noticeably than water for the same temperature change. This magnified effect makes the liquid level in the straw easily visible, indicating the temperature variations.

The science of temperature

The science of temperature can get confusing because it’s not necessarily something we can see with our eyes.

Temperature is not so much a matter of “hot” and “cold”, but is a measurement of the kinetic energy of molecules or particles around what we are measuring.

Higher temperature = higher kinetic energy

Lower temperature = lower kinetic energy

As temperature changes, the behavior of particles also changes. Here are some examples:

  • Solids: At high temperatures, solid objects can expand, melt, or even boil (become a gas). Conversely, low temperatures can make solids brittle.
  • Liquids: As liquids heat up, their molecules move faster, making the liquid flow more easily (becoming less viscous). Cooling them down slows down the molecules, making them thicker.
  • Gases: Gases readily expand with increasing temperature and contract with decreasing temperature. This principle is used in many applications, like hot air balloons and car engines.

When explaining this to little kids, try to keep things light and fun. For example: when talking about kinetic energy (the energy associated with the motion of an object), run from one side of the room to another and encourage them to do the same. That’s kinetic energy at work!

Thermal expansion and contraction

We are making a liquid-in-glass thermometer in this experiment, which typically uses either mercury or alcohol (although mercury is more often used). Since most people have access to rubbing alcohol, we are using it for our experiment.

Alcohol expands and contracts at a higher rate than water does (known as the coefficient of thermal expansion) due to the temperature around it changing. This helps us to see temperature changes in the thermometer much easier.

When the temperature around the thermometer is hotter, the alcohol/water mixture expands.

When the temperature around the thermometer is lower, the alcohol/water mixture contracts.

This is why we see the liquid mixture go down the bottle in cooler temperatures and go up the bottle in warmer temperatures.

Observation skills

Since we do this experiment over time, it builds up observation skills in young children.

They have to make an initial observation (marking the room temperature) and go outside several times throughout the day to make observations and take measurements.

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