Question

Which one of the following statements is false? (a) temperature is a state function (b) work is a state function (c) change in the state depends upon initial and final state (d) work appears at the boundary of the system

Short answer

The false statement is (b) work is a state function.

Step-by-step solution

Understand State Functions

A state function is a property whose value does not depend on the path taken to reach that specific value. Examples of state functions include temperature, pressure, volume, and enthalpy.

Analyze Each Option

Option (a): Temperature is a state function because its value is only determined by the current state of the system. Option (b): Work is not a state function because it depends on the path taken between the initial and final states. Option (c): Change in the state (such as change in enthalpy or temperature) only depends on the initial and final states, characteristics of state functions. Option (d): Work is done on or by the system and it appears at the boundary, which is a correct characteristic of work.

Identify the False Statement

Since work depends on the path taken and is not a state function, statement (b) is false. All other statements are true based on their characteristics.

Key concepts

State properties

State properties, also known as state functions, are essential concepts in thermodynamics, characterized by their dependence solely on the current state of a system, irrespective of the path taken to reach that state. This means that state properties are determined by variables like temperature, pressure, and volume that define the state of the system.
When dealing with processes like heating or compressing a gas, properties such as enthalpy or internal energy are considered state functions. These properties are crucial because they provide valuable information about the system without needing to know how the system arrived there.

• Temperature: Measures the average kinetic energy of particles, a prime example of a state function.
• Pressure: The force exerted per unit area, also a state function.
• Volume: The amount of space occupied by a system.

Understanding state properties helps in predicting how a system will change when subjected to various processes or changes in conditions.

Thermodynamics

Thermodynamics is the branch of physics that deals with the relationships between heat and other forms of energy. It fundamentally explores how energy is transferred within physical systems and the laws governing these processes. Thermodynamics is based on four laws that describe how matter behaves under various conditions.
The laws are:

• First Law: Energy cannot be created or destroyed, only transferred or changed from one form to another. This law emphasizes conservation of energy.
• Second Law: Entropy, a measure of disorder, increases in an isolated system. It implies that energy tends to disperse or spread out if not hindered by external forces.
• Third Law: As temperature approaches absolute zero, the entropy of a system approaches a minimum value.

By understanding these laws, scientists and engineers can harness and manipulate processes such as heating, cooling, and converting energy forms efficiently for various applications.

Path dependence

Path dependence is a concept in contrast to state functions, where the outcome depends on the specific path taken between initial and final states, rather than being determined solely by these states. In thermodynamics, this is crucial for understanding the nature of different processes.
Examples include:

• Work: The amount of work done by or on a system depends on how the process is carried out. For instance, compressing a gas quickly versus slowly results in different work values, because work is path-dependent.
• Heat: Similar to work, the heat exchanged between a system and its surroundings can vary depending on the path, such as during isochoric or isobaric processes.

The distinction between state functions and path-dependent functions is fundamental because it illustrates how certain properties provide information that is independent of history, while others fluctuate with the conditions and methods involved in change.