Question

Given, ${D_2}O$ is known as _____________

Answer 1

First we have to know that the chemical name of ${D_2}O$ is deuterium oxide. It is basically water composed of deuterium, where deuterium is the hydrogen isotope with a mass double that of ordinary hydrogen.

Complete answer:
${D_2}O$ is known as heavy water. Because, it is a compound which is made up of oxygen and deuterium, a heavier isotope of hydrogen which is represented by ${}^2H$ or $D$.
Heavy water is colourless, odourless and tasteless but heavier than normal water and it has a molecular weight of about $20$ amu, whereas ordinary water has a molecular weight of about $18$ amu. The ordinary water is represented by ${H_2}O$. The molecular mass of heavy water is higher than ordinary water. Ionic compounds are less soluble in heavy water because its dielectric constant is lower than that of H₂O. Active hydrogen atoms are exchanged either partially or fully, when compounds are treated with heavy water.
Heavy water is harmful to human beings, plants and animals and also it retards the growth of living organisms.

Note:
The molar mass of heavy water is greater than normal water, because atomic mass of deuterium is more than that of protium. Also, there is a small difference in the boiling points of normal and heavy water. The boiling point of normal water is $373\;K$ whereas that of heavy water is $374.42\,K$ at normal atmospheric pressure.