INTENSIVE AND EXTENSIVE PROPERTIES
THERMODYNAMIC PROPERTIES
- The macroscopic or bulk properties of a system can be divided into two parts :-
(a) Extensive properties
(b) Intensive properties
(a) Extensive properties
The properties of a system whose value depends on the quantity or size of matter are called extensive properties.
( i.e., extensive properties depends on the amount of substance or substances present in the system )
For example – mass, volume, number of moles, internal energy, Gibbs free energy, enthalpy, entropy etc.
(b) Intensive properties
The property of a system that are independent of the quantity or size of matter present in the system are called as extensive properties.
(i.e., intensive properties don’t depend on the amount of substance present in the system )
For example – temperature, pressure, density, concentration, viscosity, refractive index, surface tension, specific heat, boiling point, freezing point etc.
Note:-
- Extensive properties of a single (pure) substance will depend on the number of moles (n) of the substance present and also on any two of three variables pressure, volume and temperature ( P, V & T called independent variables )
- If number of moles (n) is kept constant, the extensive properties of the system will depend only on the two independent variables.
- Molar properties of a system are Intensive properties. For example – molar volume (Vm), molar heat capacity (Cm) etc.
Molar property, (\(\mathcal X_m\)) is the value of an extensive property \(\mathcal X\) of the system for 1 mole of the substance.
If n = amount of matter, then $$\mathcal X_m = \frac{\mathcal X}{n}$$ ,viz., independent of the amount of matter.
Distinction between Extensive and Intensive properties :
Consider a gas enclosed in a container of volume V & temperature T.
Let us make a partition of the container such that the volume is halved (V/2) in each part. Now on measuring the temperature, it will still remains T for each part.
Hence volume is an extensive property and temperature is an intensive property.