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  • St Pauls NS

Science Week in 3rd + 4th Class

The children in 3rd and 4th class were very busy during Science Week (November 8th - 15th). They carried out a variety of experiments and had great fun predicting what the results of the experiments would be.

Colour Change Walking Water Experiment

The children used cups, tissue paper, food colouring and water to complete this experiment. They laid out the cups as in the picture and put water and food colouring in every other cup with a folded piece of tissue in each cup moving into the next cup. The result of the experiment wasn't clear straight away but after leaving the cups as they were overnight, the children were quite surprised in the morning when they saw how things had changed.

The water has moved from the original cups to the empty cups through a process called capillary action - Water is able to move against the force of gravity because water molecules stick to each other and they stick to the fibers of the tissue paper. As water molecules are attracted to the fibers of the paper towel, they pull other water molecules with them. The adhesive forces between the water and the fibers of the paper towel are stronger than the cohesive forces between the water molecules. This allows water to travel from one cup to another.

Water, Oil and Food Colouring Experiment

The children used two cups, water in one and oil in the other and added a few drops of food colouring to the oil. They mixed the oil together with the food colouring and then poured it into the cup with the water. This is what happened:

This experiment is all about density. Density is a measure of how much something weighs (it’s mass) by how much space it takes up (it’s volume). Oil and water don’t mix because the water molecules are more attracted to each other than the oil. Oil is also less dense than water, which causes the oil to float on top of the water, creating two distinct layers. Liquid food colouring is water-based, which is why it doesn’t mix with the oil even when you stir it. Instead the food colouring breaks up into small droplets which become temporarily suspended (floating) within the oil. These droplets are denser than the oil and so they gradually fall though the oil and enter the water. (

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