Question

An example of an extensive property is:
A. temperature
B. internal energy
C. viscosity
D. molar heat capacity

Answer 1

Hint: Think about the definitions of both intensive and extensive properties. Extensive properties depend on the amount of mass present. Intensive properties are inherent and will stay the same even if the amount of mass is changed.

Complete step by step answer:
First let us look at the definition of intensive and extensive properties and some of their examples.
- An intensive property of a substance will not depend on the mass of the substance present. Examples include, melting point, boiling point, density, etc.
- An extensive property of a substance will change as per the changes in the amount of substance or mass of the substance. Examples include, volume, mass, energy, etc.
Now let us look at each of the given options.
- Temperature
If we measure the temperature of 1 gram of any substance and 1 kilogram of the same substance in the same conditions, we will see that there will be no change in temperature in both these masses. This intuitively means that temperature does not depend on mass and is an intensive property.
- Internal energy
It is the energy that is associated with each individual molecule and its motion at the microscopic level. It is the energy of a system that is the summation of the individual energies of each molecule. Thus, if the number of molecules in a system increases, its mass, along with its internal energy, will increase. This means that internal energy depends on mass and is an extensive property.
- Viscosity
It is defined as the resistance experienced by two layers of molecules against the uniform flow of the fluid. This property too, is associated with sheets of molecules. But adding numerous sheets or layers of molecules on top of each other will not affect the resistance between two layers, it will remain constant. Thus, viscosity is an intensive property.
- Molar heat capacity
This is a value that is defined as the amount of heat required to increase the temperature of 1 mole of a substance by one unit. Even if the amount of substance is increased, the heat required per mole will be the same. Thus, this is an extensive property.

Hence, the correct answer is ‘B. Internal Energy’.

Note: The term in option ‘D. Molar heat capacity’ contains the word ‘molar’. This can be misleading as molar indicates a relation to the amount of substance. But it is a property that is defined per amount of substance. Thus, it is an intensive property and not extensive.
The term ‘heat capacity’ on the other hand is an extensive property. Since, the amount of heat required to increase the temperature of an arbitrary volume of substance by one unit of temperature will vary according to the mass.