Science Experiment: Hot and Cold Water

The science will amaze you if you just look close enough to things that surround you. What do you think would happen if you put hot and cold water in one container without mixing? Would "hot-air-balloon" principle work underwater where we heat water instead of air? We have done two cool experiments to answer those questions.
Water changes density depending on the temperature. So much so that cold water would not mix with hot water if you place it carefully in one container. The molecules in hot water are excited by the energy, and they move faster. So when they bump into one another, they bounce further away, leaving big gaps. This means that now the same volume of water has fewer molecules and weights less. The opposite happens with cold water making its density a bit higher.
Although the density difference is not that great, we can still see how hot water floats at the top while cold water stays at the bottom in our experiments. And this slight density difference has a significant impact on natural phenomena such as ocean currents.