Tag: evaporation

Questions Related to evaporation

If the temperature is high then what is the rate of evaporation?

physics the kinetic model of matter evaporation heat, internal energy and work phase change

  1. Higher

  2. Lower

  3. Same

  4. None

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Correct Option: A
Explanation:

If temperature is high then kinetic energy of the molecules will be high and rate of evaporation is higher.

What happens to the rate of evaporation when there is more exposed surface area of liquid?

physics the kinetic model of matter evaporation heat, internal energy and work phase change

  1. It decreases gradually

  2. It increases

  3. Remains same

  4. It decreases rapidly

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Correct Option: B
Explanation:

Evaporation is a process in which some molecules of a liquid, which have greater kinetic energy, escape from the liquid and enter the atmosphere.

When the surface area exposed is more, the molecules get greater opportunity to escape. Hence more molecules escape and rate of evaporation increases.

Which of the following does not affect the rate of evaporation?

physics the kinetic model of matter evaporation heat, internal energy and work phase change

  1. Pressure on evaporating substance

  2. Exposed surface area of the evaporating substance

  3. Shape of the evaporating substance

  4. Temperature

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Correct Option: C
Explanation:

Evaporation is a process in which some molecules of a liquid, which have greater kinetic energy, escape from the liquid and enter the atmosphere.

If pressure is greater, the molecules need greater energy to overcome the pressure and hence evaporation decreases with increase in pressure.
Due to more surface area, more molecules get a chance to escape, hence faster is the evaporation.
At higher temperature, molecules have greater kinetic energy, hence can easily escape the liquid.
But shape of the surface of the liquid doesn't affect evaporation.

Why skin feels dry in an air-conditioned room?

physics the kinetic model of matter evaporation heat, internal energy and work phase change

  1. Because the rate of evaporation decreases with lower humidity.

  2. Because the rate of evaporation increases with lower humidity.

  3. Because the rate of evaporation remains same with lower humidity.

  4. Because the rate of evaporation increases with higher humidity.

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Correct Option: B
Explanation:

Evaporation is a process in which some molecules of a liquid, which have greater kinetic energy, escape from the liquid and enter the atmosphere.

When the humidity is lower, the air's capacity to absorb vapour is greater. The adhesive force of attraction between liquid molecules increases and more molecules escape into the atmosphere. Hence evaporation is greater in dry air.

The moving air from the hair dryer removes the molecules of liquids as soon as they escape from the surface of your  hair.
Which factor of evaporation is responsible for the above example?

physics the kinetic model of matter evaporation heat, internal energy and work phase change

  1. Temperature

  2. Motion of air

  3. Nature of liquid

  4. Humidity of surrounding

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Correct Option: B
Explanation:

Evaporation is a process in which some molecules of a liquid, which have greater kinetic energy, escape from the liquid and enter the atmosphere.

Evaporation occurs faster at a higher temperature.
The wind of the hairdryer being hotter than room temperature, speeds up the evaporation process.

Choose the correct statements from the following

physics the kinetic model of matter evaporation heat, internal energy and work phase change

  1. Evaporation takes place from the surface of a liquid at all temperatures.

  2. The rate of evaporation depends upon the area of the exposed surface of the liquid, nature of the liquid and its temperature.

  3. The rate of evaporation depends on the pressure to which the liquid is subjected.

  4. The cooling produced in evaporation is a consequence of the fact that a liquid has latent heat.

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Correct Option: A,B,C,D
Explanation:

Evaporation is a type of vaporization of a liquid that occurs from the surface of a liquid into a gaseous phase. So there is loss of energy due to latent heat of the liquid.

For molecules of a liquid to evaporate, they must be located near the surface, they have to be moving in the proper direction, and have sufficient kinetic energy to overcome liquid-phase inter-molecular forces. When only a small proportion of the molecules meet these criteria, the rate of evaporation is low. Since the kinetic energy of a molecule is proportional to its temperature, evaporation proceeds more quickly at higher temperatures and high surface area.
Evaporation happens faster if there is less exertion on the surface keeping the molecules from launching themselves.
So all the options are correct.

Water evaporates under atmospheric pressure. Without changing the temperature, the same water is placed in a partial vacuum. The rate of evaporation will

physics the kinetic model of matter evaporation heat, internal energy and work phase change

  1. increase

  2. drop to zero

  3. decrease

  4. remain unaffected

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Correct Option: A
Explanation:
In partial vacuum, the pressure is very less.
According to Le-chatelier's principle on decreasing pressure, volume increases so more water converts into gas (vapour).

Soda bottles are made of thick glass so that they can withstand an increase in :

physics the kinetic model of matter evaporation heat, internal energy and work phase change

  1. pressure during summer

  2. temperature during summer

  3. viscosity

  4. potential energy

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Correct Option: A
Explanation:
Gas, liquid and solid expand on heating.
Gas expands the max. due to free of gas molecules or almost zero force of attraction between them. On heating they gain K.E. and move up to any place. This gives expansion of gases.
The pressure of gas inside closed container increases upon heating. This is seen that soda bottle explodes in summer. So the air made up of thick glass so that they can withstand pressure.

A fan produces a feeling of comfort because:

physics the kinetic model of matter evaporation heat, internal energy and work phase change

  1. A fan supplies cool air

  2. Of the evaporation of sweat

  3. Fan increase the humidity in air

  4. Fan decrease the humidity in air

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Correct Option: B
Explanation:

A fan produces a feeling of comfort because of evaporation of sweat because on hot day, our body sweats to loose heat through the evaporation of moisture.In still air evaporation is slow. A fan or breeze helps by replacing hot humid air with cooler dries air that allow for more evaporation


When the temperature of water rises, the rate of evaporation decreases. State whether true or false.

physics the kinetic model of matter evaporation heat, internal energy and work phase change

  1. True

  2. False

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Correct Option: B
Explanation:
The statement if False.
Actually, rate of evaporation of a liquid decreases as the temperature decreases. As intermolecular force increase rate of evaporation decreases. This happens because intermolecular force make it less likely for the molecules on the surface to escape from liquid and become vapour gas. As temperature increases rate of evaporation increases.