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Wow your friends with a miniature crisp packet. It’s just like the real life one… but tiny.

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This activity requires adult supervision.
You will need:

• A crisp packet
• An oven
• A baking tray
• Oven gloves
  

First, empty the crisp packet and rinse it out to remove all the crumbs. Place it on a baking tray and flatten it out. Now turn your oven on, with the temperature turned to 150C. Put the baking tray in straight away, so that it heats up slowly. Watch the crisp packet carefully. You’ll see it begin to shrink and wrinkle up. Ask your adult helper to open the oven and, wearing oven gloves, flatten it down whenever it looks like its curling too much. After a few minutes, turn the heat up a little. Keep checking on the crisp packet, and flattening it down. After around ten minutes the crisp packet should have shrunk to about a quarter of its original size. At this point you can take it out the oven and let it cool down. Now the only question is, what are you going to do with it? Make a key ring? Sew it onto your jeans? Or make a whole selection and sew them into a bag?!

This looks like a magic trick but it isn’t… it’s pure science.

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You will need:

• A plastic beaker
• Some water
• A piece of card, with one shiny side e.g. a postcard

Fill a plastic beaker with water, and cover it with the card, shiny side down. Now take a deep breath, place your hand on the card, and turn the card-and-cup upside down. Here comes the magic/science. Hold onto the top (previously the bottom) of the cup, and remove the hand that was under the card … Ta-dah! The card and the water should both stay put.

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What’s happening?
There are two things going on here; one is to do with the properties of water and the other is to do with the properties of air.

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Firstly, water is actually quite sticky and so has something called ‘surface tension’. This ‘surface tension’ can sometimes act as a seal, which is exactly what it’s doing here with the card.

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Secondly, the air around us, believe it or not, can push on things. And it pushes in all directions; up, down, left and right. Well, all directions it can reach!

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In this ‘trick’ the water has made a seal with card, which means the air can only really push on the bottom of the card (because the top part is covered by the cup), and it’s this upwards push on the bottom of the card that keeps the card (and the water) in place. If you break the seal by pulling the card down, you allow air into the cup. And this means the air can now reach and so push on all parts of the card again and so the card (and the water) fall.

How to become Master of the Playground in one easy step!

You will need:

• An empty drinks can
• 100ml of water or any other liquid.

Challenge your friends to balance an empty drinks can on its edge. This is extremely hard to do when it’s empty.

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Now pour in the liquid. As you can show, it’s now easy to balance on its edge - and it looks rather spooky at that angle too. You can even spin it around …

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What’s happening?
An object only ever falls over if its ‘centre of gravity’ (or ‘balancing point’) has nothing underneath it, supporting it.

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The ‘centre of gravity’ of an empty drinks can is approximately right in its centre, and in this position it doesn’t take much tilting for the ‘centre of gravity’ to end up reaching over the can’s base. And so it’s fairly easy for the can to topple over.

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When you add water to the can, you’re lowering its ‘centre of gravity’, which means you have to tilt the can much more before the ‘centre of gravity’ reaches over the base. This makes the can much harder to tip over, and so easier to balance.

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And it’s the same for everything, not just drink cans. Think about riding on a wobbly platform like a skateboard, surfboard or snowboard, and what do you do to keep your balance? You bend your knees! And the reason this works is because when you bend your knees you're actually lowering your centre of gravity.

Here’s a startling demonstration that really does make your hand look as though it’s got a hole through the centre.

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All you need is an A4 sheet of paper.

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Roll the paper up on its short side, to make a short tube. Now hold it up to one eye, telescope style. Hold your other hand out flat, palm towards you, and right next to the tube, about half way along. Keep both eyes open and look straight ahead… what do you see?

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You may have to move your flattened hand closer or further away, but at a certain point it will look like you have a hole right though your hand.

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What’s happening?
Your two eyes are in different positions, so they see slightly different views. Usually they’re looking at the same image but from slightly different angles. However in this case, they are actually looking at totally different things. One eye is looking down the tube while the other is looking at your hand. These two views are combined by your brain… giving you the unusual sight of a hole through your hand.