Adiabatic expansion

Definition

Adiabatic expansion is a process in which a gas expands without exchanging heat with its surroundings. During this expansion, the internal energy of the gas decreases, resulting in a drop in temperature.

5 Must Know Facts For Your Next Test

1. The first law of thermodynamics for adiabatic processes is given by the equation $\Delta U = -W$, where $\Delta U$ is the change in internal energy and $W$ is the work done by the gas.
2. For an ideal gas undergoing adiabatic expansion, the relationship between pressure and volume can be expressed as $PV^\gamma = \text{constant}$, where $\gamma = \frac{C_p}{C_v}$ (the heat capacity ratio).
3. In an adiabatic process, there is no heat transfer ($Q = 0$), meaning all changes in internal energy are due to work done.
4. The temperature of an ideal gas decreases during adiabatic expansion because its internal energy drops.
5. An adiabatic process can be either reversible or irreversible; however, for ideal gases, reversible adiabatic processes are often considered due to their simplicity.

Review Questions

• What happens to the temperature of an ideal gas during adiabatic expansion?
• How does the first law of thermodynamics apply to adiabatic processes?
• What is the relationship between pressure and volume in an ideal gas undergoing adiabatic expansion?

Related terms

Isothermal Process: A thermodynamic process that occurs at a constant temperature.

Heat Capacity Ratio (\gamma): The ratio of the specific heat at constant pressure ($C_p$) to the specific heat at constant volume ($C_v$), denoted as $\gamma = \frac{C_p}{C_v}$.

Internal Energy: The total energy contained within a system due to molecular motion and interactions.