Question

The process of evaporation causes :

• A. Heating
• B. Cooling
• C. Dryness
• D. None of the above

Hint:

Evaporation is when liquid turns to gas from the surface.
This process needs energy (heat) for the molecules to escape.
The liquid takes this heat energy from itself and its surroundings.
When heat is removed, things get cooler. So, evaporation causes a {cooling effect}. Examples: Sweating cools you down; water in an earthen pot cools.

Answer 1

The Correct Option is B

Concept: Evaporation is the process by which a liquid changes into its vapor (gas) phase at its surface, at a temperature below its boiling point. This phase change requires energy. Step 1: Energy Requirement for Evaporation For liquid molecules to escape from the surface and enter the gas phase, they need to overcome the intermolecular attractive forces holding them in the liquid. This requires energy. This energy is known as the latent heat of vaporization. Step 2: Source of Energy for Evaporation The energy required for evaporation is absorbed from the surroundings. This includes:
The liquid itself.
The surface from which the liquid is evaporating.
The immediate surrounding air. Step 3: The Cooling Effect During evaporation, the molecules with higher kinetic energy are more likely to escape from the liquid surface. When these higher-energy molecules leave, the average kinetic energy of the remaining molecules in the liquid decreases. Since temperature is a measure of the average kinetic energy of the particles, a decrease in average kinetic energy results in a decrease in the temperature of the liquid. Thus, the liquid (and its immediate surroundings from which heat is absorbed) cools down. This is why sweating cools the body: as sweat evaporates from the skin, it takes heat from the body, leading to a cooling sensation. Similarly, water in an earthen pot stays cool due to evaporation from its porous surface. Step 4: Analyzing the options
(1) Heating: Incorrect. Evaporation absorbs heat, leading to cooling.
(2) Cooling: Correct. Evaporation is a cooling process because the escaping molecules take energy (latent heat of vaporization) away from the remaining liquid and its surroundings.
(3) Dryness: While evaporation leads to the removal of liquid and can cause something to become dry, "dryness" itself is a state or condition, not a direct thermal effect like heating or cooling. The question asks what the *process* of evaporation causes in terms of thermal effect.
(4) None of the above: Incorrect, as cooling is the correct effect. Therefore, the process of evaporation causes cooling.