How fun is this chemical traffic light experiment!? Liquid changes colour from green to red and later to yellow. The best part is it is repeatable. Just shake the bottle to start again. For this experiment you would need: - Dye called indigo carmine 0.05g - Caustic soda (Sodium hydroxide) 2.5g - Glucose (dextrose) 1.5g - Water 125 ml If the colours stop changing, just open the bottle for more oxygen to get inside and add a bit more of indigo carmine.