Hot Water Density Experiment

This simple density science experiment starts with placing two glasses with yellow water on top of two glasses with blue water. When we remove cards that separate coloured water, colours on the right do not mix, but they do mix quickly on the left. Magic secret hides in the temperature of the water. Hot water is less dense than cold water, so it rises to the top as oil would. But in case hot water is already on top, it does not move anywhere, and colours do not mix.