Fizzy Rockets

In this demo experiment from our school workshop series, your students will learn about some of the basic physical and chemical forces behind rockets and explosions.

Read on to find out more!

You will need

Alka Seltzer or other fizzing tablets, vitamin tube or chewing gum canister, water

Watch the video and try it out yourself.

(Video made by Niamh Hickey)

Here’s the science…

The secret is in the fizzing tablet! If you have ever mixed baking soda with vinegar, that’s the same as this chemical reaction. Look at the ingredients of AlkaSeltzer and you will see that it contains citric acid and bicarbonate of soda (baking soda). When you put the tablet in water, the acid and baking soda mix and react to produce bubbles of carbon dioxide gas. When the lid is on, this gas builds up so much pressure inside the canister/tube that the gas pops the lid off. So the gas creates a force on the lid. The lid is the path of least resistance for the gas pressure building up inside, because the other sides of the canister are sealed and stronger.

If you tried varying the water temperature, you will have noticed that the temperature is important to the reaction. Warm water speeds up the reaction, and cooler water slows down the reaction, so it takes longer to build up enough pressure to pop off the lid.

But there is important physics going on here, as well as chemistry! Have you heard of Newton’s Third Law: It says that for every reaction there is an equal and opposite reaction. That is what causes the lid to fly up into the air. This is the same thing that happens when exhaust gases from a rocket’s engine flow downwards from the spacecraft towards the ground exerting a force. This in turn causes a reaction force or thrust in the opposite direction. The reactions launches the rocket upwards towards the stratosphere!

Wanna know more about rockets and space travel?

Check out other related activities on our site

Katherine Johnson and Space Travel

Homemade rockets