How to Grow a Rainbow Science Challenge Number Seven

Did you know that you can grow your own rainbow?
You will need a scientific process called the capillary action. This action happens when a liquid moves up through a hollow tube or into a spongy, solid material. It happens when three forces work together: cohesion, adhesion and surface tension.
Water molecules like to stick to each other – this is called cohesion. They also like to stick to solids in a process called adhesion.
In this experiment, you are going to use kitchen roll. The fibres in kitchen roll have lots of little holes. Water is absorbed through the kitchen roll because when the first water molecule adheres to it and begins to move upward, it pulls the next water molecule up with it, like a chain.

You will need:
• Kitchen roll/paper towel
• Felt-tip pens
• Two small bowls of water
• Paperclip
• Thread

What To Do:

  1. Cut the kitchen roll into the shape of a rainbow.
  2. At each end, use the felt-tip pens to colour a rainbow about 2cm up from the bottom. Remember the order of the colours: red, orange, yellow, green, blue, indigo, violet.
  3. Attach the paperclip to the top of the rainbow and tie a piece of thread to it. This will allow you to hold your rainbow.
  4. Add water to the two bowls.
  5. Hold the rainbow with both ends slightly submerged into each bowl of water and watch your rainbow grow.

Words To Learn:
• capillary action
• adhesion
• cohesion
• absorbed

Dwayne sent in this wonderful rainbow – fabulous!

3 Comments

  1. it was a fun, interesting and exciting experiment.I saw the capillary action of the water. when I dipped the paper into the water, I saw the how the water was absorbing by the paper. Then the colours started to move upwards through the adhesion and cohesion.in cohesion water molecules joining together.In adhesion water molecules stick to the paper.

  2. I really want to do that! It sounds awesome! How does the rainbow grow up the paper? I can not wait to find and try out!

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