Rainbow activities to try at home

These science experiments can be carried out at home, with a few easily accessible materials. Gather your friends, and give them a try.

Underwater fireworks

Materials needed

Tall clear glass

Water

2 tbsp vegetable oil

Food colouring

Plastic cup

Fork

Method

Fill a tall clear glass to the top with warm water.

In a plastic cup, pour two tablespoons of vegetable oil. Next, add a few drops of food colouring of your choice. Give it a mix with a fork. You will see the coloured liquid break up into smaller drops.

Pour the oil and food colouring mix into the tall glass of water.

Now, watch the food colouring slowly sink in the glass, with each droplet expanding outward as it falls, resembling fireworks falling into the water. You can try the same experiment with two-three colours.

Science behind it

Food colouring dissolves in water, but not in oil. When you stir it in oil, it ends up breaking the coloured droplets. Oil is less dense in water, so when the oil mixture is poured into the water, oil floats on top. But the food colour sinks past the oil and mixes with the water, dropping to the bottom.

Rainbow oobleck

Materials needed

4 cups cornstarch

2 cups water

Food colouring (7 colours)

7 bowls

Tray

Spoon

Method

Divide the cornstarch equally into seven bowls.

Next slowly and carefully add water to the bowls. It should be in the ratio 2 parts cornstarch to ½ part water. Do not mix.

Add two drops of different food colours in each bowl. Thoroughly give each bowl a good mix. The mixture should be mildly tacky.

Once you have all the colours mixed together, start pouring the oobleck in different parts of the tray to form a rainbow. Now, you can play around with different colours and textures!

Science behind it

Oobleck is a non-Newtonian liquid. It acts as a liquid when at rest and solid when pressure is applied. When cornstarch mixes with water, it doesn’t fully dissolve. The starch remains suspended in the water. So when you move the mixture around quickly and squeeze it, the mixture hardens.

(Parental supervision advised.)