Today you are going to investigate how to grow your own rainbow. To complete this task, you will need:
Kitchen roll / paper towel
Felt tip pens
Two small bowls of water
Before you read your instructions, talk to your adult about what you think you need to do in order to grow a rainbow? After you have read the instructions, make a prediction about what you think will happen.
1. Cut your kitchen roll into the shape of a rainbow.
2. Colour a rainbow with felt tip pens about 2cm up on both sides.
3. Attach your paper clip to the top and tie a piece of thread to it. This will give you something to hold your rainbow with.
4. Fill each bowl/container with water.
5. Hold your rainbow with the ends slightly submerged in water then watch your rainbow grow!
Write an explanation about what you think has happened and why you think it has happened.
It hopefully looked like this when you were done...
A brief introduction to 'capillary action'! Water molecules like to stick to things - including themselves. Sticking to things is called adhesion and sticking to itself is called cohesion. The fibres in the kitchen roll make lots of little holes. Water is 'sucked' through the holds because of adhesion (liking to stick to other things) and cohesion (liking to stick to itself) means the rest of the water follows. The water pressure will eventually slow down and the pressure of gravity means it stops moving.