Question

We are able to sip hot tea faster in a saucer rather than a cup because- (a) Saucer has more surface area and rate of evaporation increases. (b) Saucer has less surface area and rate of evaporation increases. (c) Saucer has more surface area and rate of evaporation decreases. (d) Saucer has less surface area and rate of evaporation decreases.

Answer 1

☕ We are advised to drink tea from a saucer rather than cup, because tea cools faster in saucer because of larger surface area. Evaporation takes place faster in larger surface area, because they are directly proportional to each other.

$\sf{ \large{ \cdot \: \purple{ \: Evaporation \: \propto \: Surface \: area}}}$

☕ Reason Why?

Evaporation is the conversion of liquid state of any substance to gaseous temperature without supplying external heat from our side.

• The liquid molecules have kinetic energy and hence, they are continuously moving.
• The molecules on the surface hits with gas molecules, and gains energy. Because of excitation, they escape taking away heat from the liquid.
• So, If surface area increases, more and more molecules will get evaporate, as a result taking away heat from the body.
• As Evaporation is directly proportional to Surface area, the rate of cooling also increases. Therefore, we are advised to drink from saucer$.$

☕ Other factors:

Like Surface area, Evaporation is also affected by other factors like Wind speed, Temperature, Humidity, Nature of the liquid.

• The rate of evaporation increases with increase in temperature.
• The rate of evaporation increases with increase in wind speed. More molecules get displaced.
• Liquid with less interparticular force of attraction will evaporate faster. Acetone evaporates faster than water.
• But, Rate of Evaporation decreases with increase in humidity, because water vapour is already in the air.

✒ So, correct answer is (A)

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