Question

Which law of thermodynamics defines entropy?

Answer 1

1. The second law of thermodynamics and entropy are connected.
2. Entropy is a measurement of the system's disorders.
3. The change in entropy of the system $\left(dS\right)$ is defined as if a tiny amount of heat $\left(dQ\right)$ is applied to a system at absolute temperature $\left(T\right)$, $dS=\frac{dQ}{T}$
4. Only reversible systems can achieve this. $dQ$ is positive when the system absorbs the heat.
5. Entropy has therefore increased as a result. $\left(dQ\right)$ is negative when the system releases the heat, The system's entropy falls down.