Which one of the following is an intensive property of a thermodynamic system?

The correct option is Density.

To understand why density is the correct answer, we need to distinguish between intensive and extensive properties in thermodynamics:

1. Intensive Property: A physical property of a system that does not depend on the system size or the amount of material in the system. It remains constant regardless of how much matter is present. Examples include temperature, pressure, and density.
2. Extensive Property: A physical property that is directly proportional to the system size or the amount of material in the system. If the system is divided, the value of the property changes for each part. Examples include mass, volume, and total energy.

Let's analyze the given options:

* Mass: It depends directly on the quantity of matter. If you double the amount of substance, the mass doubles. Thus, mass is an extensive property.
* Volume: Like mass, the space occupied by a system depends on the amount of substance. Doubling the substance doubles the volume. Thus, volume is an extensive property.
* Energy: The total thermodynamic energy (such as internal energy, enthalpy, etc.) of a system scale with the size of the system. Therefore, energy is an extensive property.
* Density: Density is defined as mass per unit volume:
$$\mathrm{Density}=\frac{\mathrm{Mass}}{\mathrm{Volume}}$$
Since both mass and volume are extensive properties, their ratio (mass divided by volume) eliminates the dependence on the size of the system. For example, a small glass of water and a large bucket of water at the same temperature have different masses and volumes, but they share the exact same density. Therefore, density is an intensive property.