Saturday, March 12, 2011

Paper Towel Experiment

We conducted a neat experiment with the children which explored the idea of absorption and gravity. Using two plastic cups, a paper towel strip, and coloured water, we set up the cups in such a way so that the water would be absorbed slowly by the paper towel and moved from the higher cup to the lower one. (The pictures in this post span two school days as the water moved quite slow.)

At first, we asked the children to predict what they thought might happen to the materials. Many focused on the colour of the water and how the paper towel was turning blue. They hypothesized that the colour of the water had something to do with whatever was going to happen over the course of the experiment. In reality, the water is coloured blue only to help it stand out as it's moved from cup to cup. It would move the exact same way even if it wasn't coloured. 

By the end of the day, the children realized that the paper towel had become totally saturated with water and a few drops of liquid had pooled in the bottom cup. When asked to explain why this happened, a few children realized that the paper towel had "sucked up and spit out" the water. One child compared the paper towel to a vacuum cleaner. Many children agreed and thought more water would materialize in the bottom cup as time went on. 

When we returned to school the next day half the water had been moved from the top cup and the children enthusiastically agreed that the paper towel had sucked the water up. They came up with the word 'absorb' to describe this process.

We left the cups out again over this past weekend and when children returned to school on Monday they found that the water had totally evaporated, leaving a blue strip of paper towel and no water in either cup. They were fascinated!  We are hoping to follow up this experiment with other variations where children can test various strips of materials and see if they absorb the water and move it in the same way as the original paper towel. 

This experiment is very easy to set up at home if you are looking for a March Break activity!

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