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A liquid begins to boil when…

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A liquid begins to boil when…

A. its vapor pressure is equal to the vapor pressure of its solid at the given temperature

B. molecules start escaping its surface

C. its vapor pressure equals the atmospheric pressure

D. its volume is slightly increased.




When heat is applied to water, its temperature begins to increase, and by implication, it’s vapor pressure also increases steadily until a point is reached where this vapor pressure is exactly equal to atmospheric pressure. Water begins to boil when its vapor pressure becomes equal to atmospheric pressure.

Now for the right answer to the above question:

  1. Option A is incorrect. nothing like vapor pressure of solid.
  2. Option B is incorrect. evaporation can occur at any temperature, molecules of water can leave the surface even before the boiling point is attained.
  3. C is correct. When vapor pressure equals atmospheric pressure, boiling begins.
  4. D is not the correct answer. Increase in volume of water does not translate into boiling.


You may please note these/this:

  • Evaporation can occur even before boiling point is attained, this is because water molecules on the immediate surface could gain sufficient energy to escape.
  • Please note that evaporation is simply the escape of water vapor from the surface of water at any temperature.
  • While evaporation can occur at any temperature, boiling on the other hand occurs at a specific temperature called BOILING POINT.

Use the questions and answers session to raise further questions and deal more on this topic…

/ culled from 2017 JAMB-UTME Chemistry question 8 /

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