Question

At high altitudes, water boils at a lower temperature because?
a.) The atmospheric pressure is high at high altitudes.
b.) The viscosity of water is reduced at high altitudes.
c.) The atmospheric pressure is low at high altitudes.
d.) The surface tension of water is reduced at high altitudes.

Answer 1

Hint: You should know that the normal boiling point of a liquid is the temperature at which its vapor is equal to one atmosphere (760 torr). Remember that the boiling point increases as the number of carbons increases.


Complete step by step solution: Generally all liquids have a boiling point which may vary with surrounding and system. The atmospheric pressure of a gas above a liquid affects the boiling point. The greater the pressure, the more energy is required for liquids to boil, and the apparently higher the boiling point.

As we know the evaporation of water at elevated temperatures is the same at high altitude and as well as the low altitude. But: As soon as the vapor pressure of the liquid becomes higher than ambient pressure, bubbles of pure vapor can occur under the liquid surface. So when the liquid boils, it no longer only loses molecules through its top interface. A liquid generally boils when its vapor pressure becomes equal to the atmospheric pressure. So as we can see lower the atmospheric pressure lower will be the boiling point. Hence water boils at a temperature less than 100 Degree C.

In simple words the higher you go, the lower the air pressure. The lower the air pressure, the less energy required to resist the pressure.

Therefore, the boiling point of water depends on the atmospheric pressure at that altitude. At high altitudes, the pressure is lower. Hence, option C is the required answer.

Note: Remember that a gas cannot boil. But it can only condense. Due to which a gas cannot have a boiling point. Because if it’s a gas, then it’s already boiled, for example, steam is a form of water, which boils at 100 Degree C.