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JAMB Chemistry 1997 Question 8

Question 8

Kinetic Theory and States of Matter

The temperature of a body decreases when drops of liquid placed on it evaporate because

  1. A.the atmospheric vapour pressure has a cooling effect on the body
  2. B.a temperature gradient exists between the drops of liquid and the body causing the latter to evaporate
  3. C.the heat of vaporization is drawn from the body causing it to cool
  4. D.the random motion of the liquid molecules causes a cooling effect on the body.
Show the answer and explanation

Answer: C (the heat of vaporization is drawn from the body causing it to cool)

Explanation

Evaporating molecules need energy (latent heat of vaporization). They take this heat from the body they are on, so the body cools.