Which of the following process/ processes release heat ?
(i) Condensation (ii) Vaporisation (iii) Freezing (iv) Melting
Correct option is :

Question

Accepted Answer

Option 4, which states that both (i) Condensation and (iii) Freezing release heat, is the correct answer. Let's explore why this is the case and why the other options are incorrect.

1. **Condensation (i)**: This process involves the transformation of a gas into a liquid. During condensation, the molecules in the gas lose energy and slow down, releasing heat in the process. This release of heat is why condensation is considered an exothermic process.

2. **Freezing (iii)**: Freezing is the process where a liquid turns into a solid. As the liquid cools and solidifies, it releases heat to the surroundings. This release of heat is characteristic of exothermic processes, making freezing a process that releases heat.

Now, let's examine why the other options are incorrect:

- **Option 1: Only (i)** - This option is incorrect because it ignores the fact that freezing (iii) also releases heat. Both condensation and freezing are exothermic processes, so this option does not fully capture the processes that release heat.

- **Option 2: Only (iv)** - Melting (iv) is the process where a solid turns into a liquid. This process requires the absorption of heat to break the bonds holding the solid together, making it an endothermic process. Therefore, melting does not release heat, making this option incorrect.

- **Option 3: (ii) and (iii)** - Vaporisation (ii) is the process where a liquid turns into a gas. This process requires the absorption of heat to overcome the intermolecular forces in the liquid, making it an endothermic process. Since vaporisation absorbs heat rather than releases it, this option is incorrect.

In conclusion, Option 4 is correct because both condensation and freezing are processes that release heat, aligning with the characteristics of exothermic reactions.