As seen on ITV’s Alan Titchmarsh show

After Wendy’s appearance on ITV’s Alan Titchmarsh Show on Wednesday 26th October, here is more information about the experiments demonstrated. For links to more experiments from the previous show on 5th October, scroll down…

 

Colour changing milk

What you need:

  • Full fat milk at room temperature
  • Food colouring
  • A plate or shallow dish
  • Cotton buds
  • Washing up liquid

 

What to do:

Pour a small amount of milk onto the plate – about 1 cm deep. Carefully put small drops of food colouring at different points on the surface. Now pick up the cotton bud and carefully put a drop of washing up liquid on the end and dip it into the centre of the milk.

 

What happens?

The colours rush across the surface of the milk and start to mix in all sorts of weird and wonderful ways. Washing up liquid is a kind of detergent, and detergent likes to join together water with fat (or grease) which is why it is so good at cleaning dishes! The washing up liquid tries to get the water and fat in the milk to mix and as it does this it creates currents through the milk. This movement in the milk takes the food colouring with it to create the crazy mix of colours.

 

Invisible marbles

What you need:

  • Water beads/jelly marbles (available in larger gardening stores, florists or online from www.waterbubbles.co.uk)
  • Water
  • A tall clear container or glass vase

 

What to do:

Put the beads in a tall glass of water and wait. It takes about 4 hours for the beads to absorb water, less if you use warm water. Once they are about the size of a marble they should have become almost invisible in the water. They get about 200 times bigger so you will need a container large enough to hold them when they expand. Once you have them hidden in the water you can just plunge your hand in a ‘magically’ pull out the hidden marbles.

 

What happens?

The marbles are made of a very absorbent polymer (just a long chain of molecules) and they take in about 200 times their own volume in water. When they are fully grown then are made up of more than 99% water. Light bends when it travels through different things and this is called refraction. The light refracts through the water and the marbles in exactly the same way so you can’t see where they are. When the marbles aren’t in water the light travels through the air and then bends when it hits the marbles. This means you can see them when they are out of water but not when they are completely surrounded by it.

 

 

Tea bag rocket

NB Children should not do this experiment without close adult supervision

What you need:

  • Tea bags (the one-cup kind with string and tag)
  • Scissors
  • Matches or a lighter
  • Heat proof plate or chopping board

 

What you do:

Cut the top of the tea bag off at the end where the tag is attached and carefully open out the bag and empty out the tea. You should have a long cylinder of empty tea bag. Stand this upright on the heat-resistant plate or board. Make sure you have no flammable materials too close to the experiment. Now light the cylinder at the top and stand back.

 

What happens?

The tea bag burns from the top down, heating the air as it goes. The warm air in the cylinder is more spread out than the cold air around it and so it rises. As it rises it takes the remains of the tea bag with it up into the air.

 

 

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