Intensive and Extensive Property
The properties of matter can be divided into physical and chemical properties. The physical properties are further of two types that include intensive and extensive properties. These terms were first used by Richard C. Tolman in 1917. To measure the physical properties, we don't need to change the chemical identity of a substance.
Intensive property refers to a physical property that does not change with the change in the amount of matter, which means it does not depend on the size or mass of the substance, e.g., the boiling point of water is 100 degrees centigrade and it remains the same for 100 ml or 500 ml water. So, the boiling point is an intensive property.
On the other hand, an extensive property is a physical property of matter that depends on the size or mass of a substance. We can say that it depends on the amount of substance present, such as mass, size and volume. However, the ratio of two extensive properties is an intensive property such as the ratio of mass and volume (mass/ volume) is density (intensive property).
The term extensive is derived from the Latin word extensivus. Some other common examples of intensive properties are hardness, density, boiling point, pressure, color, refractive index, concentration, and more.
As per IUPAC, the definition of extensive property is that it is a property whose magnitude is additive for subsystems. It means it changes (increases or decreases) as the substance grow large or small. So, it is directly proportional to the size or mass of the substance.
The definition of intensive property as per IUPAC; it is a property whose magnitude is independent of the size of the system. It is the local physical property that does not change with a change in the amount or size of a substance.
A simple example of understanding intensive property is the temperature of a system in thermal equilibrium where the temperature of all parts of the system remains the same. Similarly, if a homogenous system is divided into two equal parts, the density remains the same but the volume and mass are divided in half.
How to identify Intensive or Extensive property
The easy way to identify an intensive or extensive property is that take two identical samples of a substance and combine them. If the value of physical property gets doubled, it is an extensive property, e.g. 3m long + 3m long = 6m long or 5 gm + 5 gm = 10 gm mass; so the length and mass of a substance are extensive properties. On the contrary, if the property remains unchanged by changing the size, it is an intensive property, e.g., the density of 50 gm iron with be same as the density of 100 gm iron, and so density is an extensive property as it remains the same even if the mass of iron is doubled.
Note: When an extensive property is divided by volume or mass, it becomes an intensive property.
Weight / volume = specific weight (intensive property) Volume / mass = specific volume (intensive property) Mass / volume = specific mass or density (intensive property)
Difference between Intensive and Extensive property