Difference Between Heavy Water and Normal Water

Main Difference – Heavy Water vs Normal Water

About 71% of earth’s crust is covered with water, but a very little percentage of it is drinkable. Water is an essential component for all living beings in their day to day life. Living beings cannot survive without water. The presence of water is the major reason why there is life on earth. Normal water is composed of H₂O molecules, which are called water molecule. But there is another type of water which is called heavy water. The main difference between heavy water and normal water is that heavy water is composed of d₂o molecules whereas normal water is composed of h₂o molecules.

Key Areas Covered

1. What is Heavy Water
      – Definition, Properties, Uses
2. What is Normal Water
      – Definition, Properties, Uses
3. What are the Similarities Between Heavy Water and Normal Water
      – Outline of Common Features
4. What is the Difference Between Heavy Water and Normal Water
      – Comparison of Key Differences

Key Terms: Deuterium, Heavy Water, Hydrogen, Normal Water, Protium

What is Heavy Water

Heavy water is a form of water that contains D₂O molecules. These D₂O molecules are composed of Deuterium atoms and oxygen atoms. Normally, water is composed of H₂O molecules. The reason for the name “Heavy water” is that Deuterium (D) is heavier than Hydrogen (H) that is present in normal water.

Deuterium is an isotope of Hydrogen. It is composed of a neutron and a proton in its nucleus. Therefore, the atomic mass of Deuterium is 2.014 amu. That is because atomic mass is the sum of the number of neutrons and protons. However, it is composed of one electron, just like the hydrogen atom.

Unlike Hydrogen, Deuterium is less abundant on earth. Its abundance is about 0.015%. The D₂O molecule has an angular geometry. The molar mass of D₂O is about 20 g/mol. The density of heavy water is about 1.107 g/mL. The boiling point of heavy water is 101.4^oC. Heavy water is completely miscible with water.

Figure 1: The chemical structure of D₂O

There can be other types of heavy water and semi-heavy water forms as well. For example, semi heavy water is composed of HDO molecules. This consists of a hydrogen atom, a deuterium atom, and an oxygen atom. If not, there can be heavy oxygen water. That means this heavy water is composed of water molecules that are made out of hydrogen atoms and heavy oxygen isotopes.

There are many applications of heavy water. Heavy water is used as the deuterium source for the production of different organic compounds.

What is Normal Water

Normal water is the most abundant form of water which is composed of H₂O molecules. This type of water is composed of H₂O molecules that are made out of Protium atoms which are the commonest and most stable isotopes of hydrogen.

Figure 2: The Chemical Structure of H₂O

Protium is composed of one proton; there are no neutrons present. It also has a single electron. The abundance of protium on earth is about 99%. The atomic mass of protium is about 1.00794 amu. It is considered as the normal hydrogen since it is the most abundant form on earth.

The molar mass of normal water is about 18 g/mol. Its boiling point is 100^oC. Below 0^oC, normal water exists in solid form as ice. Above its boiling point, water molecules exist in the gaseous phase as steam. There are a number of unique properties of water which makes it an essential component of life. Such properties include surface tension, ability to form strong hydrogen bonds, etc.

Similarities Between Heavy Water and Normal Water

• Both heavy water and normal water are composed of isotopes of hydrogen.
• Both are composed of oxygen atoms.
• Both are liquids at room temperature.
• Both are odorless and colorless liquids.

Difference Between Heavy Water and Normal Water

Definition

Heavy Water: Heavy water is a form of water that contains D₂O molecules.

Normal Water: Normal water is the most abundant form of water which is composed of H₂O molecules.

Molecules

Heavy Water:  Heavy water is composed of D₂O molecules.

Normal Water:  Normal water is composed of H₂O molecules.

Molar Mass

Heavy Water: The molar mass of heavy water is about 20 g/mol.

Normal Water:  The molar mass of normal water is about 18 g/mol.

Boiling Point

Heavy Water:  The boiling point of heavy water is about 101.4^oC.

Normal Water: The boiling point of normal water is 100^oC.

Density

Heavy Water: The density of heavy water is comparatively high.

Normal Water:  The density of normal water is comparatively less.

Ice

Heavy Water:  The ice cubes formed from heavy water will sink in liquid water due to high density.

Normal Water: The ice cubes formed from normal water will float on liquid water due to its low density.

Conclusion

Although heavy water and normal water are two forms of water, normal water is mostly used in day to day needs. This is because the body cannot hold a high amount of heavy water due to its high weight and density. This is a major difference between heavy water and normal water.  Heavy water is used in some synthesis processes where a Deuterium source is needed.

References:

1. “Heavy water.” Wikipedia. Wikimedia Foundation, 01 July 2017. Web. Available here. 24 July 2017. 
2. Helmenstine, Ph.D. Anne Marie. “What Is Heavy Water?” ThoughtCo. N.p., n.d. Web. Available here. 24 July 2017. 

Image Courtesy:

1. “Deuterium-oxide-2D” By Tritium-oxide-2D.png: Benjah-bmm27derivative work: Kronf (talk) – Tritium-oxide-2D.png (Public Domain) via Commons Wikimedia
2. “H2O – 2d” By Crazytonyi – Own work (Public Domain) via Commons Wikimedia