** Mass vs Volume **

Mass and volume are fundamental properties of matter, and these two properties are related to each other. Mass will be proportional to volume when the density is a constant. If anything possesses a volume, it also has a mass.

**Mass**

Mass is a property of matter which is a measure of inertia. It also gives an idea of how much matter is there in the object. It is one of the three fundamental dimensions (M) of mechanics (time – T and length – L are the other two fundamental dimensions). SI unit (International System of Units) for mass is ‘kilogram’. However, the units such as gram, milligram and metric ton are used in appropriate situations. Imperial units system (also known as British units) uses units like pound, grain and stone to measure the mass.

Usually we take the mass as an unchanging property. Mass of an object is the same at earth, moon or at any place. However, mass can be changed at higher velocities according to the theory of relativity proposed by Albert Einstein. According to another theory of him mass can be converted into energy. This principle is used in nuclear power generation.

**Volume**

Volume measures the amount of three dimensional space occupied by an object. SI unit for measuring volume is ‘cubic meter’. However, ‘litre’, which is equal to a thousandth of a cubic meter (or a cubic decimeter), is the most popular measuring unit for volume. Ounce, pint, and gallon are the units in the imperial system for volume. One millilitre is equal to a cubic centimeter. Volume has dimensions of L^{3} (length x length x length).

Unlike the mass, volume changes according to the external conditions. As an example, volume of a sample of gas depends on the air pressure. Volume of a solid can be changed when it is melted.

There are mathematical expressions to calculate the volume of general shapes (length x height x width for a cuboid and 4/3 x πr^{3} for a sphere). For objects with complicated shapes, measuring the amount of displaced liquid is the best option.

1. Although mass of an object is independent of its phase (solid, liquid or gas) or external conditions, volume changes with those parameters. 2. Mass is a fundamental dimension in mechanics and volume is not. It is derived from another fundamental dimension- length (L). 3. Mass is measured in kilograms and volume is in cubic meters. 4. Although mass can be converted into energy, it is not possible for volume. 5. According to relativity, mass increases at higher velocities where volume is decreased. 6. Although there is conservation of mass in a chemical reaction, there is no volume conservation. |