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Movement In The Water

Energy and heat are related properties and this experiment shows why, with a splash of colour

Australian Curriculum links

  • Science > Physical Sciences > Year 3 > ACSSU049

You'll need

  • Two clear glasses
  • Hot and cold water (boiling and icy works best!)
  • Red and blue food dye

Try this

  1. Fill one of the glasses with cold water and the other with hot water. Tap temperatures will work, but a greater temperature difference will show a greater effect. Try using chilled water and recently boiled water.
  2. Add a couple of drops of red food colouring to the hot water and a couple of drops of blue food colouring to the cold water.
  3. Watch the movement of the colour in the two glasses.

Further investigation

Try comparing warm water to the hot and cold water. Is the difference noticeable?

What’s happening?

Heat is a type of energy. When heat energy is given to something it usually gets hotter. If heat energy is taken away it will become colder. The faster the particles in an object are moving, the more heat energy an object has. The slower the particles are moving,the less heat energy an object has.

In this case, the warm water has more energy than the cold water. When the food dye is added, the particles of water are moving faster, which causes the movement of the food dye and dispersal of the colour to happen more quickly.

It’s important to remember that objects don’t always feel hot when they have heat energy. In this case, the heat energy is present inboth the warm and cold water and this is shown by the food colouring moving throughout the water at both temperatures.