The second law of thermodynamics stated in terms of entropy

Definition

The second law of thermodynamics states that in any closed system, the total entropy can only increase or remain constant over time. Entropy is a measure of disorder or randomness, and this law implies that energy transformations are not perfectly efficient.

5 Must Know Facts For Your Next Test

1. Entropy, denoted by $S$, tends to increase in isolated systems.
2. The second law of thermodynamics suggests that natural processes have a preferred direction: from order to disorder.
3. In terms of entropy, the second law implies that energy has a tendency to disperse and become less available for doing work.
4. The concept of entropy helps explain why certain processes are irreversible, such as heat flowing spontaneously from hot to cold regions.
5. Mathematically, the change in entropy ($\Delta S$) for a reversible process is given by $\Delta S = \int \frac{dQ_{rev}}{T}$.

Related terms

Entropy:

A measure of disorder or randomness in a system. Higher entropy signifies greater disorder.

Reversible Process:

A hypothetical process that occurs infinitely slowly so that the system remains in thermal equilibrium with its surroundings.

$dQ_{rev}$: $dQ_{rev}$ represents an infinitesimal amount of heat added reversibly to a system at temperature $T$.