You will need one film canister per person to make your alka-seltzer rocket. You can decorate the film canisters with paints to personalise them. Or even make a rocket body, nose cone and fins out of paper – they do get very soggy though! If you can’t get your hands on film canisters, you could experiment with other small containers with tight fitting snap on lids.
Make your alka-seltzer rocket
Break the Alka-Seltzer tablets in half and give a piece to each person to place in their film canister. Check that all the canisters have tight-fitting lids (very important!). When ready to launch the first rocket, add 1cm of water, snap the lid on and make sure the seal is tight. Quickly turn the canister upside-down (so the lid is at the bottom) and place it on a flat surface. Now stand back!
When water is added to the Alka-Seltzer tablet it gives off bubbles of carbon dioxide gas. When the lid is fitted tightly to the canister this gas is contained within an enclosed space. As more gas is given off the pressure inside the canister rises until there is enough force to overcome the seal of the lid. The built up pressure exerts enough force to shoot the canister into the air, forming the rocket. They go pretty high and make a very satisfying pop. The warmer the water you add, the quicker the reaction. So make sure it’s not too warm or else you won’t have time to get the lid on and move away.
Extra safety tips:
- Although this can be done in a large space indoors, it gets pretty messy so is best done outside.
- Take it in turns to set off the rockets and designate an area as the rocket launch pad so you don’t have rockets launching all over the place. They’re small but they go fast, so there is a potential hazard.
Take it further
Test out some more fun science with the egg drop challenge.
