Q. What do you mean by ‘Heavy water’?
Ans. Heavy water is the oxide of heavier isotope of hydrogen, i.e. deuterium and is having the chemical formula D2O. It can be prepared from ordinary water by carrying out its prolonged electrolysis. Heavy water retards the growth of many plants and animals. For example, tobacco seeds do not germinate in heavy water. Some small fish and tadpoles also can’t survive in this water. But the water finds its usefulness in nuclear reactors where it is used as a moderator as well as a coolant.