What is Evaporation ? Effects of Evaporation.
What is Evaporation ?
Evaporation is the process by which a liquid changes into vapour at any temperature below its boiling point, mainly from the surface of the liquid.
How Does Evaporation Cause Cooling ?
- During evaporation, high-energy particles at the surface of a liquid escape into the air as vapour.
- These particles take heat energy from the liquid or the surrounding surface.
- As a result, the remaining liquid loses energy and becomes cooler.
This loss of heat causes cooling.
Evaporation and Our Body (Sweating)
- Our body produces sweat during hot weather or exercise.
- When sweat evaporates, it absorbs heat from our skin.
- This lowers body temperature and cools us down.
Everyday Examples of Evaporation Causing Cooling
- Sweating after exercise cools our body.
- Water in an earthen pot (matka) becomes cool in summer due to evaporation through tiny pores.
- We feel cool under a fan because evaporation of sweat increases.
- Alcohol or perfume feels cool when applied to the skin as it evaporates quickly.
Evaporation in Our Daily Life
- Drying of clothes.
- Cooling of water in earthen pots (matka).
- Drying of wet umbrellas.
- Drying of salted fish, vegetables, and fruits.
Importance of Evaporation
- Helps in cooling our body naturally.
- Useful in preserving food.
- Plays an important role in daily activities and weather processes.
In short: Evaporation absorbs heat, causes cooling, and is extremely useful in our everyday life.
Q 1.. What is evaporation ?
A) Change of solid into liquid B) Change of liquid into vapour below its boiling point C) Change of gas into liquid D) Change of solid directly into gas
Ans: B) Change of liquid into vapour below its boiling point
Explanation: Evaporation is a surface process where a liquid changes into vapour at temperatures lower than its boiling point.
Q 2. From where does evaporation mainly occur ?
A) Bottom of the liquid B) Middle of the liquid C) Surface of the liquid D) Inside the container
Ans: C) Surface of the liquid
Explanation: Only the particles at the surface can gain enough energy to escape into the air.
Q 3. Why does evaporation cause cooling ?
A) Liquid gains heat B) Low-energy particles escape C) High-energy particles take heat away D) Temperature increases
Ans: C) High-energy particles take heat away
Explanation: Escaping particles absorb heat energy, making the remaining liquid cooler.
Q 4.How does sweating cool our body ?
A) Sweat increases body heat B) Sweat absorbs heat when it evaporates C) Sweat stops evaporation D) Sweat freezes the skin
Ans: B) Sweat absorbs heat when it evaporates
Explanation: Evaporation of sweat removes heat from the skin and lowers body temperature.
Q 5. Why does water in an earthen pot (matka) become cool in summer ?
A) The pot produces cold air B) Water freezes inside C) Evaporation occurs through tiny pores D) The pot reflects sunlight
Ans: C) Evaporation occurs through tiny pores
Explanation: Water evaporates through the pores, taking heat away and cooling the remaining water.
Q 6. Why do we feel cool under a fan ?
A) Fan lowers room temperature B) Fan increases evaporation of sweat C) Fan adds moisture D) Fan stops sweating
Ans: B) Fan increases evaporation of sweat
Explanation: Faster evaporation removes more heat from our body.
Q 7. Which substance feels cool when applied because it evaporates quickly?
A) Oil B) Honey C) Alcohol or perfume D) Butter
Ans: C) Alcohol or perfume
Explanation: These liquids evaporate rapidly and absorb heat from the skin.
Q 8. Which of the following is NOT an example of evaporation?
A) Drying of clothes B) Drying of wet umbrellas C) Cooling of water in a matka D) Melting of ice
Ans: D) Melting of ice
Explanation: Melting is the change from solid to liquid, not liquid to vapour.
Q 9. Which of the following is an importance of evaporation?
A) Helps in natural cooling B) Preserves food C) Important in weather processes D) All of the above
Ans: D) All of the above
Explanation: Evaporation is essential for cooling, food preservation, and the water cycle.
Q 10. What happens to the remaining liquid after evaporation?
A) It becomes hotter B) It loses energy and becomes cooler C) It turns into solid D) Its volume increases
Ans: B) It loses energy and becomes cooler
Explanation: The escaping particles carry heat away, lowering the temperature of the liquid.