Homemade Lava Lamp!
You will need:
Alka Seltzer tablet
Add the food colouring to 120ml (1/2 cup) of water.
Pour the oil into the bottle/glass until about 3/4 full.
Add the coloured water to the bottle/glass being sure to leave a few centimetres of space at top.
Break up the Alka Seltzer tablet (do not put them in your mouth) into a few pieces then drop in a small piece. More can be added for a bigger reaction or when the bubbling starts to slow down.