I saw this exploring water surface tension experiment on Instagram and just thought it was incredibly and that we definitely had to try it out. In my mind it is never too early to start doing STEM activities with little ones, and home schooling has been a great way to do this.
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To do this exploring water surface tension experiment you will need:
- Wax paper
- Food colouring
- Different bowls
Choose how many different colours you want, then mix up the food colouring with the water. We went with 5 – red, yellow, green, blue, and purple.
Lay out a piece of wax paper, I taped it down over a piece of white paper. This was only to make the coloured water show up better. At the bottom of the sheet, I drew 5 different bases for the different coloured water to be moved into.
Using the pipette put dots of the water all over the wax paper.
Then using a toothpick get your little one to drag the coloured water into the correct base.
BB was fascinated with what was going on in this exploring water surface tension experiment. Although I didn’t go into the science behind it, we did talk about how this doesn’t happen when you put water onto a normal piece of paper. We put one drop onto the paper underneath and tried to move it. Which, obviously, didn’t work.
The science behind it:
Water drops have what looks like a “skin” holding it together. It is actually more like a net-like pattern on the surface called surface tension. This surface tension is because the water molecules are attracted each other (this is called cohesion).
When you poke the toothpick into the drop of water, rather than breaking the surface tension, the water sticks to the wood. This is called adhesion. The water is then able to be moved around the wax paper. Interestingly there is a sort of attraction between the wax paper and the water drop. If you were to turn the wax paper upside down the droplet will stay in place.
You can break the surface tension by adding a bit of soap to the end of the toothpick before you touch the water drop. The force of the cohesion between molecules has been reduced, so the drop changes shape.
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