When we sit next to a bonfire, we don’t wonder why it’s warm. But what if we created heat without any fire or electricity? In this experiment, we will do just that using an exothermic chemical reaction. We will also learn how reactions release energy and how scientists speed them up!

Materials

Bowl
¼ cup of hydrogen peroxide
1 tsp yeast
Thermometer
Stirring stick
Notebook and pen to record results

Time Estimated:

20 minutes

Directions:

First, pour the hydrogen peroxide into the bowl.
Place the thermometer inside the bowl and wait two minutes, or long enough for it to read the temperature.
Write this number in your notebook.
Now, add the yeast and stir for one minute. Be careful not to hit the thermometer!
Touch the sides of the bow. Does it feel warmer? Write down the new temperature in your notebook.
Subtract the first temperature from the new one. How much did it change?

Think Like a Scientist!

Why does the temperature change?
Why does the mixture start bubbling when we add the yeast?

How Does it Work?

Hydrogen peroxide is made of the same elements as water (hydrogen and oxygen), but has an extra oxygen molecule. Over time, it naturally breaks down into water and oxygen. However substances like yeast speed this process up, and are called catalysts in chemistry! When we mixed the yeast with the hydrogen peroxide, the water and oxygen molecules separated very quickly, and the escaping oxygen created bubbles on the surface. The temperature changed because energy was released when the bonds between the water and the extra oxygen molecules were broken. Chemists call this an exothermic reaction, or one that releases energy as either heat or light. For some extra fun, you can add dish soap to the mixture and see what happens as the oxygen is released!

Further Exploration:

Chemists study the ways substances interact with each other, which includes chemical reactions such as this. Exothermic reactions, or those that release energy, are important because they can heat up their surroundings. Fire is a great example of an exothermic reaction. However, sometimes we need less extreme ways to create heat. For example, chemists working in the food industry use exothermic reactions such as the one we did to create self-heating packaging.

Anticipated concerns

If you add dish soap to the mixture, it might get messy! Be outside or in an area where spills are okay.

Looking for more fun at-home STEM activities for your young scientist? Check out our workbook full of exciting science experiments and empowering activities!

Learn more and purchase today!