Which of the following is correct about the process of evaporation?

Correct option is B

The correct answer is (b) It increases as the surface area increases.

Explanation:

• Evaporation is a surface phenomenon where liquid changes into vapour at any temperature below its boiling point.

• Since it takes place at the surface, an increase in surface area allows more particles to escape from the liquid phase into the gaseous phase simultaneously, thereby increasing the rate of evaporation.

• This is why we spread out wet clothes to dry them faster; increasing the area exposed to air speeds up the drying process.

• According to NCERT Class 9 Science, the rate of evaporation is influenced by four main factors: surface area, temperature, humidity, and wind speed.

• Evaporation leads to a cooling effect because the liquid particles absorb energy from the surroundings to compensate for the energy lost during the process.

Information Booster:

• In an earthen pot (matka), water evaporates through small pores in the clay, which absorbs heat from the water inside, keeping it cool.

• High humidity (the amount of water vapour in the air) slows down evaporation because the air is already saturated and cannot easily take in more moisture.

Additional Knowledge:

It does not depend on the level of moisture (Option a)

• This is incorrect. The rate of evaporation is inversely proportional to humidity. If the air is humid (high moisture), the rate of evaporation decreases significantly.

It decreases with increase in wind speed (Option c)

• This is incorrect. With an increase in wind speed, the particles of water vapour move away with the wind, decreasing the amount of water vapour in the surrounding area and thus increasing the rate of evaporation.

It decreases as the temperature increases (Option d)

• This is incorrect. With an increase in temperature, more particles get enough kinetic energy to go into the vapour state, thus increasing the rate of evaporation.