Fun science based activity to explore the build up of carbon-dioxide in a confined space - Added by GGNZ Programme Team
On the inside of the film canister lid blu-tac the berrocca tablet so that it will remain attached to the inside of the lid
Add a small amount of cold water to the film canister, put the lid on (ensuring that the berrocca remains attached to the lid). Place the film canister upside down on the ground, with everyone standing 2-3 metres away. Wait and watch what happens - the film canister will explode upwards into the air with a 'pop'
Experiment - what happens if you put less water, more water, warm water? What happens if you use half a tablet?
The Science Behind It:
- The berrocca tablet (containing sodium bicarbonate and citric acid) mixes with the water, releasing carbon dioxide. When this reaction takes place in an open glass of water, the carbon dioxide escapes slowly into the atmosphere, over a period of several minutes as the tablet dissolves, so there is no change in pressure. But if the gas is prevented from leaving, by constraining it inside a container like the sealed film canister, the pressure will build up, storing energy. Eventually, the pressure becomes sufficiently high to force open the lid, and all of the gas - and the energy stored in it - is released at once with a "pop", launching the cannister into the air
- It's like fireworks, the build up of energy is contained inside a firework, building up and then will explode with a 'bang'