During the long summer holidays, it's hard to think of things to keep your older kids amused. It's not possible to spend every day out and about, so when you're at home why not try some simple science experiments? Your kids will have fun. You will, too. Promise.
One of my son's favourite things to do since he was around 7 years old is make film canister rockets. In the summer, we often pack up a bag of everything we need and head to the park to shoot them off. Inevitably, we get a few passers-by who want to join in as well so I always bring extra. We also do them inside in the winter months, as well. Be warned: if you have low ceilings they may need cleaning afterwards.
Here are the instructions from Planet SciCast which is a brilliant site filled with short science films made by kids as well as experiments you can do at home.What you need
1. Waterproof table covering. (if you're doing it indoors)
3. Sticky Tape and / or glue.
4. Lightweight coloured paper.
5. Other bits to decorate the rocket if you have them.
6. Film canister with lid (clear film canisters where the lid presses inside work the best. if you don't have any handy, go to your local photo developing shop and ask for some of their 'empties'. I've got tons of them for free this way).
7. Baking Soda (sodium bicarbonate).
8. Vinegar (or alternatively lemon juice).
10. Toilet paper
What you do
For the Rocket covering:
1. Cut a strip of paper wide enough to go completely round your canister and longer than the canister to give your rocket some height. Line the paper up with the open end of the canister and sticky tape the paper along the length of the canister, making sure the paper doesn't get in the way of the canister lid. Then roll the canister round and secure the paper again to make a tube around the canister. If the paper is too long it may be heavy so you can trim the non-canister end of your tube now. You may have to experiment a bit to get it completely right for your weight of paper.
2. Make a largish circle with the paper, and cut out a segment. Joining up the edges of the segment, secure with tape for the nose cone. The bigger the segment you cut out, the sharper the nose cone. Secure to the non-canister end of the rocket with tape.
3. Decorate rocket (optional).
For the Rocket engine:
1. Take the lid off the film canister, holding your rocket upside down.
2. Measure three teaspoons of vinegar into the canister.
3. Take a sheet of toilet paper and place it on top of the canister. Press it down to form a small well but not so far that it touches the vinegar! The aim is to keep the two ingredients apart.
4. Place a teaspoonful of baking soda in the well.
5. Press the lid on tightly and trim the excess toilet paper from the edges.
6. Do not turn it over yet and definitely DO NOT SHAKE IT! You don't want it to go off and hit you in the eye.
Make sure you do the next bit where you've put the waterproof table covering as mess will ensue.
7. Turn the canister over and place it lid-down on the table top then retreat to a safe distance i.e. a few metres away.
Brace yourself. It will take about 20 seconds or so to launch.
What's going on
The vinegar and baking soda (sodium bicarbonate) react together giving off carbon dioxide gas. The gas builds up until it forces the lid off the film canister. The gas pushes downwards which in turn (thanks to Newton and his Third Law) causes the canister and rocket covering to be forced upwards, in much the same way as real rockets work.
If it still doesn't look rockety enough for you then checkout the fantastic website for BBC Norfolk. Norfolk astronomer and Chairman of the Norwich Astronomical Society Mark Thompson gives instructions on building a rocket using a similar device and there's a template to make the rocket body, nose cone and fins.
Special Safety Advice
Caution: this rocket pops up unexpectedly, don't hover over it. If you just use the canister without the rocket covering then it really flies with force, retire a few metres away and it's safest to do this outside or somewhere with a lot of headroom. Adult supervision required.
You can watch a short film showing the film canister rockets being made and launched here.