Question

Why is deuterium oxide called “heavy water”?

Answer 1

Deuterium oxide (D₂O) is commonly referred to as "heavy water" because it contains a higher atomic mass than regular water (H₂O). In regular water, each hydrogen atom has an atomic mass of approximately 1 (specifically, 1.008 atomic mass units). However, deuterium, a heavier isotope of hydrogen, has an atomic mass of about 2 (specifically, 2.014 atomic mass units).

Since deuterium oxide consists of two deuterium atoms and one oxygen atom, its molecular weight is significantly greater than that of regular water. This increased mass gives it the name "heavy water." The presence of deuterium alters some of the physical and chemical properties of the water, such as its density, boiling point, and melting point, making it distinguishable from ordinary water.