Question

Which of the following thermodynamic variables is extensive?
A) Pressure
B) Density
C) Temperature
D) Mass

Answer 1

Hint: According to thermodynamics, the variables were classified into two types. They are extensive variables and intensive variables. Intensive variables do not depend upon the quantity of the substance whereas the extensive variables depend upon the quantity of the substances.

Complete answer:
Thermodynamics is an important branch of science that deals with variables like heat, work, and internal energy. As discussed in the hint, an extensive variable depends upon the quantity of the substances.
Let’s look at the given options and check which variables depend on the quantity.

A) Pressure is the variable that does not depend upon the quantity of substances. Thus, it is an example of extensive variables.

B) Density is constant for every substance. For example, water has a density of $1gm{\left(cm\right)}^{-3}$ . Thus, it is an example of extensive variables.

C) Temperature is also an example of extensive variables as when water is heated, all the water molecules have the same temperature irrespective of quantity or amount.

D) Mass is an example of extensive variables, as the mass of any substance changes with the amount present in it. As it is a quantity that depends upon the amount, it is regarded as an extensive variable.

In the given options, mass is considered an extensive variable. So, Option (D) is correct.

Note:
Most of the variables which are frequently used in thermodynamics like enthalpy, energy, and volume depend upon the mass of the substance. Thus, the quantities or variables that depend upon the mass are known as extensive variables.