STEM Rainbow science: Exploring the concept of absorption

Wednesday 13th June 2018

Today our science experience explored the concept of absorption. Our planting experiences have led us to explore capillary action, that is how water can travel through the stem of a plant upwards to the leaves. Our aim was to visually demonstrate the action of water absorbing and travelling against gravity. Here, we presented the children with a travelling waters experiment to see how paper towels absorb water and travel from a series of plastic cups to create a rainbow of colours.

The supplies we used included: 

+ Small plastic cups or glasses

+ Paper towels

+ Food colouring in primary colours

+ Water 

First we took the paper towels and fold them up into strips. We then put one end in the coloured water and one end into the empty cup. As the water soaks up the paper towel, it brought all of the colours with it making a wonderful rainbow. We were completely mesmerised with process as we watched what was occurring. The coloured water begin to crawl up the paper towel quite rapidly and the colours began to meet and merge together.  

We asked the children:

+ What do you think will happen to the water?

+ What is happening now?

+ Why do you think the colours are changing?

+ When you loo at the stem, where does the water go? 

Finnley predicted "The paper change colour." Milo said, “The water is moving…there….there.” As Milo pointed and observed the colours moving in an upward direction. Penelope added “The colours touch and it turns into a new colour.”  How it works is that the water moves up the paper towels through a process called capillary action. The paper towel is made from fibers and the water is able to travel through the gaps in the fibers. The gaps in the paper towel act like capillary tubes and pull the water upward.

This is what helps water climb from a plant’s roots to the leaves at the top of the plant or tree. The water is able to move upward against gravity because of the attractive forces between the water and the fibers in the paper towel. The water is able to move upward against gravity because of the attractive forces between the water and the fibers in the paper towel. After we watched the colours mix together, we then removed the paper towel and observed how the paper towels had changed, looking at the variations in colour. We then took the cups and began mixing these together in a tub to see what would happen if they combined. We found that we could make brown by mixing all the water together.  

We will extend on this experience with food colouring flowers to understand how the capillary action occurs with plants and the function of the stem. We want to demonstrate how the plant takes water from the ground into the stem for the leaves and flowers to be nourished.