Entropy

Entropy

Entropy is a measure of randomness or disorder of a system and represents the unavailable energy in a process.

### Formula

$$\Delta S=\frac{Q_{rev}}{T}$$

### For Finite Change

$$\Delta S=S_2-S_1$$

### Terminologies

- S → Entropy.

- Qrev → Reversible heat transfer.

- T → Absolute temperature.

### SI Unit

$$JK^{-1}$$

### Dimensions

$$[S]=[ML^2T^{-2}K^{-1}]$$

### Conditions / Special Cases

For reversible process:

$$\Delta S=\frac{Q}{T}$$

For irreversible process:

$$\Delta S>\frac{Q}{T}$$

### Usage

- Used to determine direction and feasibility of thermodynamic processes.