Isothermal Expansion

Definition

Isothermal expansion is a thermodynamic process in which a system, such as a gas, expands while maintaining a constant temperature. This means that the system exchanges heat with its surroundings in order to keep the temperature constant during the expansion.

5 Must Know Facts For Your Next Test

1. During an isothermal expansion, the system does work on the surroundings, which results in a decrease in the internal energy of the system.
2. The change in entropy during an isothermal expansion is positive, indicating an increase in disorder or randomness within the system.
3. Isothermal expansion is a reversible process, meaning that it can be reversed without leaving any trace on the system or its surroundings.
4. The work done during an isothermal expansion is equal to the negative of the change in Helmholtz free energy, which is a measure of the maximum amount of useful work that can be extracted from a system at constant temperature.
5. Isothermal expansion is an important concept in the study of the Second Law of Thermodynamics, as it helps to explain the spontaneous nature of certain processes and the direction of heat flow in a system.

Review Questions

• Explain how the change in entropy during an isothermal expansion is related to the Second Law of Thermodynamics.
  • The Second Law of Thermodynamics states that the entropy of an isolated system not in equilibrium will tend to increase over time, approaching a maximum value at equilibrium. During an isothermal expansion, the system exchanges heat with its surroundings in order to maintain a constant temperature. This exchange of heat results in an increase in the entropy of the system, which is consistent with the Second Law. The positive change in entropy during an isothermal expansion indicates an increase in the disorder or randomness within the system, which is a spontaneous process that occurs naturally.
• Describe the relationship between the work done during an isothermal expansion and the change in Helmholtz free energy.
  • The work done during an isothermal expansion is equal to the negative of the change in Helmholtz free energy, which is a measure of the maximum amount of useful work that can be extracted from a system at constant temperature. Helmholtz free energy is defined as the difference between the internal energy of a system and the product of its temperature and entropy. During an isothermal expansion, the system does work on the surroundings, which results in a decrease in the internal energy of the system. This decrease in internal energy is directly related to the change in Helmholtz free energy, and the work done can be calculated as the negative of this change.
• Analyze how the reversibility of an isothermal expansion process is related to the Second Law of Thermodynamics.
  • The reversibility of an isothermal expansion process is an important concept in the context of the Second Law of Thermodynamics. A reversible process is one that can be reversed without leaving any trace on the system or its surroundings. During an isothermal expansion, the system exchanges heat with its surroundings in order to maintain a constant temperature. This exchange of heat is a reversible process, meaning that the system can be returned to its initial state without any net change in the system or its surroundings. The reversibility of an isothermal expansion is a key feature that allows it to be used in the study of the Second Law of Thermodynamics, as it helps to explain the spontaneous nature of certain processes and the direction of heat flow in a system.

Related terms

Adiabatic Expansion: A thermodynamic process in which a system expands without exchanging heat with its surroundings, resulting in a decrease in temperature.

Entropy: A measure of the disorder or randomness in a system, which increases during spontaneous processes and is related to the Second Law of Thermodynamics.

Reversible Process: A thermodynamic process that can be reversed without leaving any trace on the system or its surroundings.