Question

state the effect of (i) surface area (ii) nature of the liquid on the rate of
evapuration​

Answer 1

✴ Evaporation:

The process of a liquid changing into gas at any temperature( below its boiling point) is called Evaporation.

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⚠️Whatever be the temperature at which Evaporation takes place, the latent heat of evaporation must be supplied whenever a liquid is changed into gas.

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⏹ How Evaporation takes place?

The particles of liquid at the surface collides with surrounding air particles, hence gains kinetic energy. Increase in kinetic energy, increases the rate of motion and the surface liquid molecules vaporise after getting excited. While, eveaportaing it takes away heat from the liquid, hence also causing cooling.

❇ Your Answer:

Factors affecting rate of evaporation:

• Nature of liquid

Different liquids have different rates of Evaporation. A liquid having weaker interparticle attractive force evaporates at a faster rate because less energy is required to overcome the attractive force.

✏ Acetone evaporates faster than water.

• Surface area of liquid ( directly proportional )

The evaporation of liquid depends on surface area. If the surface area is increased, more molecules come to the surface and rate of evaporation increases.

$\large{ \boxed{ \rm{ \red{Surface \: area \: \propto \:Rate \: of \: evaporation}}}}$

✏ a) The rate of evaporation increases when we put kerosene or petrol in an open petri dish than a container which narrow mouth.

✏ b) Clothes dry faster when they are well spread because surface area increases for Evaporation.

⏹ Other factors:

• Temperature (directly proportional)

Rate of Evaporation increases with increase in temperature. This is because with the increase in temperature more number of particles get enough energy to go into the vapour state or gaseous state.

✏ Clothes dry faster in summer than winter.

• Humidity ( Inversely proportional)

When the moisture content in air is more, than less evaporation rate decreases, because less molecules accumulate in air. The air cannot hold more than definite amount of water vapour at a given temperature.

✏ Clothes donot dry eaily during the rainy season because the rate of evaporation is less due to more moisture content.

• Wind speed ( Directly proportional )

The rate of evaporation increases with increase in wind speed because wind will replace air above the air continuously. They help in decreasing the water vapour in air, because of replacement.

✏ Clothes dry faster in windy day.

✏ Desert coolers has an exhaust fan that sucks moist air from the cooler chamber which results in greater rat roof evaporation and hence, greater cooling.

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