We learnt that unbalanced forces cause a change in the motion of an object. We used water and alka seltzer tablets to cause a pressure change in our rocket canisters.
When the Alka Seltzer tablet is added to water a chemical reaction occurs and CO2 is produced. As more CO2 is produced, the pressure inside the cannister increases until the seal of the lid is broken. The release of pressure provides the ‘push’ that launches the rocket.