Pick the correct extensive property of a thermodynamic system from the following options.
Volume
Thermodynamic Properties: Extensive vs. Intensive
In thermodynamics, properties of a system are broadly classified into two main types: extensive and intensive properties. Understanding this distinction is crucial for analyzing thermodynamic systems.
Extensive Properties Defined
Extensive properties are those properties that depend on the amount of matter or the size of the system. If you combine two identical systems, the value of an extensive property for the combined system will be the sum of its values for the individual systems. Simply put, extensive properties are additive.
- Examples: Mass, volume, total energy, number of moles, and entropy are common examples of extensive properties.
Intensive Properties Explained
On the other hand, intensive properties are those properties that do not depend on the amount of matter or the size of the system. They are uniform throughout the system, meaning their value does not change if the system is divided into smaller parts.
- Examples: Temperature, pressure, density, specific volume, and concentration are typical examples of intensive properties.
Analyzing the Given Options for Extensive Property
Let's examine each option provided to determine whether it is an extensive or an intensive property of a thermodynamic system.
| Property | Explanation | Classification |
|---|---|---|
| Temperature | If you have two identical cups of water, both at 25°C, and combine them, the resulting combined water will still be at 25°C. Temperature does not add up with the amount of substance. | Intensive Property |
| Pressure | Consider two identical gas cylinders, each at 5 atmospheres of pressure. If these are connected or combined (assuming the same volume), the pressure of the resulting system remains 5 atmospheres. Pressure does not depend on the system's size. | Intensive Property |
| Density | Density is defined as mass per unit volume ($\rho = \frac{m}{V}$). If you take a large block of a material and cut it into smaller pieces, each piece will have the same density as the original block. Density is an intensive property because it's a ratio of two extensive properties. | Intensive Property |
| Volume | Imagine you have two identical 1-liter bottles filled with water. If you pour the water from both bottles into a larger container, the total volume of water will be 2 liters. The volume has doubled because you combined two systems. This clearly indicates that volume depends on the amount of substance. | Extensive Property |
Conclusion on Extensive Property
Based on the definitions and analysis, Volume is the only property among the given options that is extensive. It directly scales with the amount of matter in the thermodynamic system.
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