Rainbow in a Glass


Density tells you how heavy a certain volume of a substance is. It decides which materials can float on water and which sink. For example, a rock will sink because its density is higher that the density of water. However, wood floats because its density is lower than that of water.

The same is true for liquids. Liquids with high densities sink, while liquids with lower densities float. We are going to use this to make a rainbow in a glass. Chocolate sauce has a highest density of the four liquids and will stay at the bottom. However, water has the lowest density and will, therefore, float on top.

You will need

  • 1 Glass
  • 1 Spoon
  • Chocolate sauce
  • Honey
  • Washing up liquid
  • Water
  • Red food colouring

What to do

  1. Start by pouring chocolate sauce into your glass until it is one quarter full.
  2. Use the spoon to carefully add the honey until your glass is half full. Do NOT stir!
  3. Now add the washing up liquid slowly and until your glass is three quarters full.
  4. In a separate glass mix water with red food colouring.
  5. Carefully add the water dropwise until your glass is full. Do NOT stir!

You can watch this experiment as a YouTube video:



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