Walking water
Glasses of coloured water linked by strips of kitchen roll: in a few hours the water climbs, crosses from glass to glass and makes new colours.
Age : age 3+
Materials
- 6 identical clear glasses : Or 5, in a line or circle.
- Kitchen roll : Strips folded lengthwise.
- Red, yellow and blue food colouring
- Water
Steps
Set up
- Arrange the glasses in a circle.
- Every other glass: fill it three quarters with water, with one colour (red, yellow, blue). The others stay empty.
- Fold strips of kitchen roll in two or three lengthwise.
- Lay each strip in an arch: one end in a full glass, the other in the empty glass next to it.
- So each empty glass gets two strips, coming from two different colours.
Watch
- See the water climb the paper in the first few minutes.
- Come back every hour: the empty glasses fill up.
- What colour appears between red and yellow? Between yellow and blue?
- Draw the result before and after.
The water climbs the kitchen roll thanks to capillary action: it creeps into the tiny spaces between the paper fibres, even upwards. That's also how water rises up plant stems.
Test other papers (newspaper, cloth napkin, printer paper) and see which makes the water "walk" fastest.
If it goes wrong
- Water doesn't climb : The end must touch the bottom of the full glass.
- Empty glass doesn't fill : The paper must reach the bottom of the empty glass.
- Brown colours : A few drops are enough.
Safety
- Colourings and glass tumblers: covered table and a grown-up nearby.