Isothermal process

Definition

An isothermal process is a thermodynamic process in which the temperature of the system remains constant. This implies that any heat added to the system is used to do work.

5 Must Know Facts For Your Next Test

1. In an isothermal process, the internal energy of an ideal gas remains constant because internal energy is a function of temperature.
2. The first law of thermodynamics, $\Delta U = Q - W$, simplifies to $Q = W$ for an isothermal process.
3. Isothermal processes are often represented on a P-V diagram as hyperbolic curves.
4. For an ideal gas undergoing an isothermal process, the product of pressure and volume (PV) remains constant ($PV = nRT$).
5. Isothermal expansion or compression requires a slow process allowing the system to exchange heat with its surroundings.

Review Questions

• What happens to the internal energy of an ideal gas during an isothermal process?
• How does the first law of thermodynamics simplify for an isothermal process?
• What shape does an isothermal process form on a P-V diagram?

Related terms

Adiabatic Process:

A thermodynamic process in which no heat is exchanged with the surroundings, implying $Q = 0$.

Isochoric Process:

A thermodynamic process at constant volume, meaning that no work is done ($W = 0$).

Cyclic Process:

A series of processes that return a system to its initial state, implying that net change in internal energy over one cycle is zero.