Evaporation from the surface of a given liquid takes place more rapidly when

Q: What is the answer to NDA (I) 2022 GAT Q53?

A. Correct — A, the temperature is high and the surface area of the liquid is large. Evaporation is a surface phenomenon in which the faster-moving molecules escape from the liquid's surface. Raising the temperature gives more molecules enough energy to escape, and a larger exposed surface area lets more molecules leave in a given time. Both factors speed up evaporation, so high temperature together with a large surface area gives the fastest rate.

(a)the temperature is high and the surface area of the liquid is large
(b)the temperature is low and the surface area of the liquid is large
(c)the temperature is low and the surface area of the liquid is small
(d)the temperature is high and the surface area of the liquid is small

Answer

Why

Correct — A, the temperature is high and the surface area of the liquid is large. Evaporation is a surface phenomenon in which the faster-moving molecules escape from the liquid's surface. Raising the temperature gives more molecules enough energy to escape, and a larger exposed surface area lets more molecules leave in a given time. Both factors speed up evaporation, so high temperature together with a large surface area gives the fastest rate.

Why the others are wrong

(b)
the temperature is low and the surface area of the liquid is large — A large surface area does help, but a low temperature slows evaporation because fewer molecules have enough energy to escape.
(c)
the temperature is low and the surface area of the liquid is small — Both conditions slow evaporation, so this gives the slowest rate — the opposite of what is asked.
(d)
the temperature is high and the surface area of the liquid is small — High temperature helps, but a small surface area limits how many molecules can escape, so the rate is slower than with a large surface area.

Concept

Evaporation is the change of a liquid to vapour at its surface, and it occurs at all temperatures (unlike boiling). Its rate rises with higher temperature, larger surface area, lower humidity and faster air movement (wind). Because the most energetic molecules leave, evaporation cools the remaining liquid.

Each option pairs two conditions. Pick the pair that both make it easier for surface molecules to escape — a high temperature (more energetic molecules) and a large surface area (more molecules exposed).

Key facts

Evaporation happens only at the surface and at any temperature, unlike boiling which occurs throughout at the boiling point.
It speeds up with higher temperature, larger surface area, lower humidity and faster wind.
Evaporation is a cooling process because it removes the fastest-moving molecules.
Wet clothes dry faster when spread out (large area) on a hot, windy day.

Wide shallow coastal salt-evaporation pans where seawater is dried in the sun to harvest salt — Salt is made by letting seawater evaporate in wide, shallow pans under the sun — deliberately maximising surface area and temperature, the very factors that speed up evaporation.Image: Bernard Spragg. NZ · Wikimedia Commons (CC0)

Study next

Evaporation versus boilingFactors affecting the rate of evaporationEvaporation causes coolingHumidity and the water cycleLatent heat of vaporization

Common traps

Confusing evaporation (surface, any temperature) with boiling (throughout, at the boiling point).
Forgetting that low humidity and faster wind also speed up evaporation.

Pairs two variables per option; choose the pair that both increase the escape of surface molecules — high temperature and large surface area.

Related PYQs

NDA_GAT_2025_I_Q1052025Open & attempt →

Condensation of water vapour into water is influenced by which of the following factor/factors? 1. Volume of air 2. Humidity 3. Temperature Select the answer using the code given below:

(a) 1 only
(b) 1 and 2 only
(c) 2 and 3 only
(d) 1, 2 and 3

Answer(d) 1, 2 and 3

Same area — the factors that control a change of state of water. That NDA item lists what influences condensation (the reverse of evaporation, involving humidity and temperature); this one asks what speeds up evaporation.

Practice

practice — not a real PYQ
Evaporation of a liquid generally causes
- (a)heating of the surroundings
- (b)cooling of the surroundings
- (c)no change in temperature
- (d)an increase in the liquid's temperature
Answer(b) cooling of the surroundings — the fastest molecules leave, lowering the average energy.
practice — not a real PYQ
Which condition makes wet clothes dry the fastest?
- (a)humid, still air
- (b)hot, dry, windy air
- (c)cold, still air
- (d)cold, humid air
Answer(b) hot, dry, windy air — high temperature, low humidity and wind all speed up evaporation.