Question

Which is an exothermic change?

• A. Salt dissolving in water
• B. Boiling
• C. Condensation
• D. Evaporation

Answer 1

The correct option is C

Condensation

The explanation for the correct options

C. Condensation

• Condensation is a process in which vapors are converted into liquid on cooling.
• Heat is released in this process.
• So, it is an exothermic process, in which heat is released.

The explanation for the incorrect options

A. salt dissolving in water

• Dissolution of salt in water requires absorption of energy, so it will be an endothermic process.

B. Boiling

• The conversion of liquid into a gas at its boiling point is called boiling.
• For example, the Boiling point of water is $100°\mathrm{C}$ at which it changes into a vapor state.
• Hence, energy will be absorbed in this process, so it will be an endothermic process.

D. Evaporation

• The conversion of liquid into gas below its boiling point is called Evaporation.
• For example, Evaporation of water from clothes after washing.
• Evaporation depends on several factors like

1. Wind speed - Higher the wind speed, the higher the evaporation.
2. Temperature - Higher the temperature, the higher the evaporation.
3. Surface area - More the surface area, the higher the evaporation.
4. Humidity - higher the humidity, the lower the evaporation.

• Hence, energy will be absorbed in this process, so it will be an endothermic process.

Hence option (C) is correct, Condensation is a process in which heat is released. So, it is an exothermic process.