Take a large glass vase or transparent mixing bowl and approximately 450g of cornflour. Pour the cornflour into the vase or bowl and slowly add water. Keep stirring and adding the water until you get a thickish mixture.
Now drop three or four pound coins into the mixture and invite your friends to ‘grab a pound’, giving them up to 10 seconds to do so.
The aim is to very slowly cut through the mixture with your fingers, grab the money and very slowly pull your hand back out. Make sure to have a towel ready as it gets messy!
The quicker your friends try to grab the money, the faster and harder the mixture will set around their hands. The cornflour and water mixture sometimes acts like a solid and acts as a liquid at other times.
How does this work? The conflour and water mix becomes a dilatent material. This means that under pressure and on mixing the cornflour becomes more viscous. Imagine the cornflour as a number of particles all separated by water, as you move your hands through the mixture you force the water molecules out creating a solid. When you stop moving your hands in the mixture you allow the water to move between the cornflour particles again producing a more liquid like material. |
