Homemade rockets rock!

Download PDF version of this activity here

Age group 3rd – 6th class
Total time: 1hr – 1.5hrs

Outline: To learn about forces, gas pressure, and chemical reactions

Links to Primary Curriculum Key Learning points
The child should be enabled to:
– identify and explore how objects and materials may be moved (Area: SESE, Science:  Forces )
– explore and experiment with the properties and characteristics of materials in making structures (Area: Arts Education, Visual Arts)
– Chemical reactions and some factors that control them
– Gas pressure as a force
– Newton’s Third Law – To every action there is an equal but opposite reaction

Notes for parents/carers and teachers

This activity can be carried out at home by a child/small group of children and an adult, by varying the types of age-appropriate tasks. The materials are available at home or easily obtainable. The activity is written out with instructions directed to the child’s parent/carer. Feel free to adapt this activity as appropriate.

What you need

Any similar container
with a tight click-shut lid will do

1-2 chewing gum canisters, Some packets of Alka Seltzer tablets, water, protective glasses/light toned sunglasses will do!, Stopwatch/timer, coloured card, scissors, tape/glue, home-made white lab coat optional, (Reuse a large old white shirt with adjusted sleeves)

1. Do you like rockets?

Open their curiosity by asking some questions like the following:

Do you like rockets? Why? Have you ever seen one blasting off? Have you ever made a rocket at home? Would you like to?

Feel free to add these interesting facts.

Did you know?

  • The Chinese invented rockets around 700 years ago while using gunpowder in their military and for fun, as fireworks.
  • Space rockets can take people into space, or can take objects like satellites into orbit.
  • For a rocket to take off, the force of its engine must be greater than the weight of the rocket.

2. What do you know about rockets and forces?

NOTE: For younger children, feel free to carry out the experiment first and then ask them some questions about what they think happened after.

Brainstorm on rockets and forces

Start with saying something like “Space rockets need lots of science like physics and chemistry to make them work. What do you think makes them blast off so fast? What helps them travel so high? ”

Brainstorm openly with them. Help them to think about the forces that a rocket engine needs to push itself off the ground. They may mention an explosion, fire or rocket fuel. This creates a force to push up the rocket, like in the experiment we will do today.

3. Making our mini-rockets

It’s best to try this somewhere you don’t mind getting things a little wet!

  1. Fill the two canisters half-way with water, and take two tablets out of a freshly opened packet of Alka Seltzers. Finely crush one of them.

2. Be ready with your timer/stopwatch. Place the whole tablet into one canister, and the crushed one into the other, without the lids on, and start your timer/stopwatch.

3. Time how long the fizzing goes on for in each canister. Write down how long this chemical reaction lasts. Why do you think the water stops bubbling? Which lasts longer? Why? Empty the contents into the sink.

4. Put on your protective glasses/sunglasses. Repeat the experiment with one canister, and this time put the lid on it immediately after you drop in a whole crushed tablet. Start timing the reaction as soon as you drop it in. Stand back, and hopefully the lid will pop off and fly high into the air.

5. Try changing the amount of the water in the canister but keeping the amount of tablet the same. You can also vary the temperature of the water (without burning yourself!) and record what happens. How does the temperature affect the speed of the reaction? Does warmer or colder water change the height the canister reaches?

6. Get creative and construct a simple paper or light card rocket around the body of the canister (Paper Rocket Design). Make some fins and add a nose cone to your rocket and watch it blast off. Remember this time, once the lid is on, place your canister upside down with the lid down on the surface. For extra pizzaz, you could add some food colouring to the water if everyone’s ok with the extra mess!
Remember to have a few spare tablets as this experiment is so much fun they’ll want to repeat it a few times!

4. How do these rockets work?

Prompt them with some questions like those below. You can then read the full explanation to them, or better still, put it into your own words.

Key questions

What do you think are the bubbles or fizzing that you saw? How did the water temperature affect your experiment? What do you think makes the canister shoot up?


The secret is in the fizzing tablet! If you have ever mixed baking soda with vinegar, that’s the same as this chemical reaction (try it out later?). Look at the ingredients of Alka Seltzer 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 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.

Sir Isaac Newton was a physicist who loved to experiment, and one of his laws tells us what is happening here. Newton’s Third Law says – for every action there is an equal and opposite reaction. So when the lid goes one way the gum canister shoots off in the opposite direction. Can you think of any other examples of Newton’s Third Law in everyday life? (e.g. balls hitting off each other in a pool table)

6. What did you like? What did you learn?

Adults and children are both welcome to answer.

What did you like most/least about this experiment?

What did you learn about forces, pressure, and chemical reactions?

What else would you like to try in this experiment if you did it again?

5. Who gets to fly real rockets?

We seem to always hear about all the men who fly around in space suits, and rockets, but what about women? We’re here to tell you about those women, because girls can also do anything they set their minds to.

Dr. Norah Patten, Irish astronaut candidate

Norah Patten was born in Co. Mayo and was fascinated by space as a child after visiting NASA when she was 11 years old. She held on to that passion for space, designing rockets for her junior certificate art project, and strategically selecting to study Aeronautical Engineering at the University of Limerick.

Elora McFall, Sophia student volunteer, and Dr. Norah Patten at Sophia’s Student Science Competition Nov. 2019

Patten was the first Irish participant at Project PoSSUM and has completed high-g flights, hypoxia training, aviation egress training and spacesuit testing and evaluations.

Samantha Cristoforetti, Italian Astronaut

Samantha Cristoforetti (born April 26, 1977) is an Italian European Space Agency astronaut, Italian Air Force pilot and engineer. She holds the record for the longest uninterrupted spaceflight by a European astronaut, and until June 2017 held the record for the longest single space flight by a woman until this was broken by Peggy Whitson and later by Christina Koch. She is also the first Italian woman in space.

Click here to watch Samantha in the Futura Space-mission

7. Extra Resources

Alka Seltzer Rocket Eruptions https://littlebinsforlittlehands.com/alka-seltzer-rocket-activity-kids

Rocket Facts for Kids https://kids.kiddle.co/Rocket

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