Number 1: The Film Canister Rocket!

We're going to start with one of my favourites; the great film canister rocket!

You'll need:

• 1 film canister (you can still get them, try Jessops or anywhere else where they still develop film). The ones white ones with the white lids work best.
• Lemon juice or vinegar (lemon juice smells nicer, but vinegar works just as well)
• Bicarbonate of Soda 
• A teaspoon
• Some toilet roll
• SAFETY SPECS!

Safety:

Wear those safety specs and this one is best done with adult supervision. 

What to do.
1) Take everything you need outside
2) Put the safety specs on and keep them on until the end.
3 Take the canister and pour in the lemon juice or vinegar until you have about 1cm worth in the bottom.

4) Take a square of toilet tissue and put it on top of the canister, gently push the tissue into the canister so that you have a small pocket in the top. Make sure the tissue doesn't touch the liquid in the bottom.

5) Next spoon in 1 teaspoons worth of bicarbonate of soda. Then snap the lid tightly back on the canister. 

6) Now you have to be quick! Grasp the canister (keep it at arms length).  Turn the canister over and give it one or two good shakes. Put it, lid down, on a surface. 

7) Stand back and watch it fly!

Whats going on?

The bicarbonate of soda reacts with the acid in the vinegar or lemon juice to produce carbon dioxide gas (and water). As more gas is made the pressure inside the canister builds up, eventually the pressure gets too much and the lid pops off. The gas escapes out and pushes the canister up. 

This is exactly the way that real rockets work (except you can't get to the moon with bicarb and vinegar as a fuel). But your rocket does follow something called 'Newton's third law of motion', which states that "every action has an equal an opposite reaction". In this case this means that the action of the gas escaping from the canister has an opposite reaction which pushes the canister into the air.