Bath Bombs

Last term in Room 1 we did a class experiment called "bath bombs". I enjoyed watching the bath bombs fizz. I found it hard to mix the oil and food colouring evenly into the dry ingredients.
Have you ever wondered how bath bombs fizz?
Mix in 10 tablespoons baking soda  4 tablespoons of cornstarch, 3 tablespoons citric acid, and 3 tablespoons of epsom salts, all in a glass bowl. With a pipette, suck up and squeeze 15- 20 drops of oil and food colouring into the dry ingredients, mixing well. Once everything is mixed and has the consistency of damp sand, pack it into a small mould. Wait overnight. In the morning it should be quite hard. Pour water in the mould with the bath bomb. As you pour in the water, it will start to fizz. The citric acid makes it feel foamy. When the reaction takes place, it makes carbon dioxide which causes the fizzing. This is a chemical reaction.