Do you remember the Making a Mint Challenge from earlier in the year? You had the chance to grow a packet of mint and see how much money you could make from it.  Well here’s your chance to do it again! Click here to send for your free pack.

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Don’t look now but they’re trying to Barbie-fy cricket balls! Fluorescent pink cricket balls will be tried out during one-day matches next season to see if they last longer than the white balls that are used now. Apparently white balls are normally used in one-day internationals but have to be changed after 34 overs because they get so battered and bashed. The white paint tends to flake off and they don't last for all 50 overs of a one-day match, so scientists want to come up with something better. They think that pink balls would be easier to see as they fly through the air. Hmmmmmm – what next? 

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Slime

This is an old favourite but now we have a film on Planet SciCast too!

You will need:

• Cornflour or custard powder (not instant custard).
• Some water.
• A bowl.
• A spoon, or your hands.
• A cup for measuring.

What to do:

1. Mix 2 cups of cornflour with 1 cup of water, making sure to stir the water in slowly so you don't get any lumps.
2. The result is a strange white (or yellow if you are using custard powder) substance that will either act like a solid (if you punch it quickly or roll it into a ball) or it will act like liquid (if you touch it gently or tip the bowl).
3. If the mixture is not doing this you may need to add a little more cornflour or a little more water.
4. If you increase the amounts of cornflour and water, you could in theory fill a bathtub with the mixture, and run across the top without falling in. (You'd have to be very quick though!)

What's happening?

The cornflour and water mixture is a mixture of solid particles suspended in a liquid, called a "colloid". When you stir the mixture slowly, the custard powder particles can move around in the water quite freely, and so the mixture acts as a liquid. When you stir the mixture faster or hold it in your hand tightly, the solid particles rub against each other causing friction. This makes them stick together and the mixture will act like a solid. If you squeeze it really hard you will squeeze some of the water out and what remains will be more or less solid.

Special Safety advice

Playing with this with your hands is perfectly safe (although if you are using custard it can leave your hands a little yellow).

This activity comes from Planet Scicast and if you want to see how it’s done then look at the clip first!

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