Can coloured water really step out of a glass and into another? What forces could be at work in this experiment that let water defy gravity and common sense?
- Get three or more glasses of the same size, and for half of them (rounded up) fill them with water.
- Add a different colour of food colouring to each glass with water in, give it a good mix.
- Now, arrange the glasses in a line so that you have a glass with water, then one without, then one with, then one without and so on.
- For each glasses pair, take a piece of paper kitchen towel and fold it in half lengthways two or three times.
- Place the kitchen towel into the glasses so that there's one bit between each adjacent glass. Now sit back - watch what happens!
Small Science Club results
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So what's happening?
What will happen is the water in the glasses will flow through the kitchen towel and into the empty glasses!
There are two important actions going on here - first of all capillary action wets the kitchen towel and carries the water from one glass and into another. Capillary action is a wicking effect, like in candles and plants. Next, a siphon effect tries to equalise the levels of the water in each glass, so it carries on flowing until each glass' water is at the same level as all the others it's connected by paper towel to. Not everyone knows this: it's gravity that makes the water find its own level, not air pressure.
If you used different food colourings you will see a lovely mixing effect in the glasses that were between two coloured glasses. Can you predict what colours will be made by mixing the differently coloured water?
What would happen if you:
- Raised the glasses with water in above those without?
- Used muddy water in one glass going to an empty one?
- Started with plain water in the empty glasses to the same level as the coloured water?