Film canister rocket

Film canister rocket

Follow these instructions to make your own film canister rocket and learn about the chemical reaction that makes it blast off.

WARNING: This activity involves a flying projectile. Make sure you have an adult with you and wear eye protection (safety glasses). Do this activity outside or in a high-ceilinged building like a hall. Never launch with anything breakable above the rocket, especially your face. Never point your canister rocket at anything, except the sky.

What you need

To do this activity you will need:

• a film canister
• baking soda (sodium bicarbonate)
• vinegar (any kind will work, but white vinegar is easiest to clean up)
• an ice cream stick or teaspoon
• a plate, saucer, tray or similar
• eye protection (glasses, sun glasses or safety goggles)
• an adult.

What to do

1. Take the lid off the film canister. Before adding the ingredients, practise putting on the lid and placing it upside down as described in step 5.
2. Put on your eye protection.
3. Pour a small amount of vinegar, about 5 millimetres deep, into the body of the canister.
4. Using the teaspoon or icecream stick, place enough baking soda to fill the recess in the lid.
5. Hold the body of the canister in one hand and the lid in the other. Quickly and firmly press the lid completely on, place the canister lid down on the plate and stand back. Make sure your plate is on a level surface. Your canister rocket will blast off seconds later. The exact timing will depend on the canister, temperature, amount of ingredients and how tightly you packed the baking soda in.
6. Have a close look at the lid and bubbling ingredients left on the plate.

What's happening

When vinegar and baking soda mix together, there is a fast chemical reaction. There are several products of the reaction, although it is the carbon dioxide gas (C0₂) that pops the lid off.
As more and more carbon dioxide is produced, the bits of carbon dioxide (called molecules) are squashed together and begin to push, or apply a force, on all the inside surfaces of the canister, including the lid.
Pressure is defined as a force over an area. In this case, it's the force of the carbon dioxide pushing over the inside area of the canister. As the carbon dioxide builds up, so does the pressure inside the canister. The pressure quickly pops the lid off.
A good way to understand what is happening is to take a deep breath in, seal your lips and slowly breathe back out into your mouth. Eventually your mouth cannot hold the pressure and your lips will unseal, letting some air out. Caution: don't overdo this as you can hurt your eardrums.
The carbon dioxide gas pushes down on the lid, although as it is sitting on the plate it can't go anywhere when it pops. The carbon dioxide is also pushing on the inside base of the canister (the top of your rocket) and this pushes it into the air.