Walking Water

What you need

• Seven clear plastic cups
• Food colouring
• Water
• Paper towels
• Scissors

Instructions

1. Line up the cups and fill every odd one with water. Stir various food colourings into the water-filled cups – e.g. red in the 1st and 7th, yellow in the 3rd, blue in the 5th.
2. Fold some paper towels to make upside-down V-shaped arches. Trim them so that they can link every cup with its neighbour, with the ends touching the bottom of the cups.
3. Wait for several hours. Water will end up in all of the cups and the colours will be mixed!

Results and Explanation

Water overcomes gravity and rises up the arches as it is attracted to the cellulose in them and to the water already absorbed. Once the arches are saturated, the water seeps out again and mixes with coloured water from the next arch to make new colours.

These experiments have not been specifically safety tested for home use but we believe them to be safe if the instructions are followed. Adult supervision or direction is recommended as appropriate. All experiments are carried out at your own risk.