The Grade Six students did Rainbow Milk experiments in Science class today. It was very cool to see the action begin when a drop of soap was added to the milk and food colouring! Here are the instructions for the experiment:
What you need:
Food colouring (4 colours)
"Secret liquid" (Soap - liquid detergent)
What to do:
- Pour milk in pie plate (about half full)
- Put one drop of each colour of food colouring in the milk. Do this very gently with lots of space between the drops.
- Put one drop of "secret liquid" in the milk and see what happens!
- Click on the following link to see a video of the experiment: Rainbow Milk - Cool Science Experiment
Pouring the milk in the pie plate.
Adding the food colouring.
The soap reduces the surface tension of the milk by dissolving the fat molecules. The surface of the milk outside the soap drop has a higher surface tension, so it pulls the surface away from that spot. The food coloring moves with the surface, streaming away from the soap drop.