Make this boat and it will bubble its way round the bath under its own power. If you bend the tube at the back to one side, you can make the boat go round a corner.
Steps to be taken
1. With scissors, make a small hole in the bottom of the plastic bottle, close to the edge.
2. Push the plastic straw through the hole until only about 1 cm sticks out. Press the straw down a little. Press plasticine round it to keep it in place and fill up the hole.
3. Shake some baking soda on to a paper tissue or piece of paper Wrap the paper round the soda and twist the ends.
4. Pour some vinegar into the bottle. Push in the paper with the soda. Put the top on as quickly as you can. Put the bottle gently into a bath of water and let go.
How it happens
Baking soda is a chemical, called sodium bicarbonate. When it mixes with vinegar, it makes a gas called carbon dioxide. When the paper gets wet in the vinegar, it untwists. The soda and vinegar mix together and make a lot of gas and foam. The gas goes out through the plastic straw and pushes the boat along.