This is the experiment every new Rocket Club member asks to do again. It costs almost nothing, it takes twenty minutes, and the pop is loud enough to make grown-ups jump. Here is how to do it safely, and why it works.
What you need
- An empty film pot with a lid that fits inside the rim
- Fizzy vitamin tablets, cut in half
- Water, card, sticky tape and scissors
- Safety goggles for everyone watching
- A grown-up, and an open space outside
How it works
The fizzy tablet is full of two powders that react when they get wet. As they react, they make a gas called carbon dioxide, the same gas that makes the bubbles in carbonated drinks.
In an open glass the gas would just bubble away. In a film pot with the lid on, it has nowhere to go. More and more gas squeezes into the small space above the water, pushing harder and harder on the lid, until the lid cannot hold any more.
When the lid pops off, the gas and water rush out of the bottom, and the pot shoots the other way. A real rocket works in exactly the same way: it pushes hot gas down, so the rocket goes up. Scientists call this an action and a reaction.
Make it fly higher
Try one change at a time and measure each flight against a wall or a fence. Does a quarter of a tablet work better than a half? What about warm water? Does a longer nose cone help it fly straight? Write your results down: that is what real scientists do.
The Rocket Club record, set by eight-year-old Priya in March, is 6.4 meters: well over the top of the hall roof. Her secret was a very pointy nose cone, a quarter of a tablet and a lot of patience while she tried twelve versions. Can you beat it? Send us your best height and we will add it to the board.
Stay safeAlways do this outside with a grown-up. Wear goggles, never lean over the rocket, and never pick it up while it is fizzing.
