Question

At high altitudes, the boiling point of water lowers because:
A)The atmospheric pressure is low
B)The temperature is low
C)The atmospheric pressure is high
D)None of these

Answer 1

To answer this question, you should recall the concept of colligative properties. Boiling point is a colligative property. With the increase in altitude, the atmosphere becomes much drier. The air has decreased levels of oxygen and atmospheric pressure, so cooking takes longer. Moisture quickly evaporates from everything.

Complete Step by step solution:
We know how boiling takes place. For boiling of water, you need to apply energy in the form of heat. As energy is transferred to the water molecules, they begin to break the bonds holding them together. The water will ultimately boil and turn into vapour when the internal vapour pressure equals the pressure exerted on it by the atmosphere. High altitudes have lower atmospheric pressure.
As you get higher up into the atmosphere the air pressure gets lower therefore, the boiling point of water will generally be at a lower temperature due to decrease in concentration of oxygen particles in air. Now as the water boils at a lower temperature at higher elevations, foods that are prepared by boiling will cook at a lower temperature, and it will take longer to cook. In cooking any material, it is required heating food to a certain temperature for a certain length of time. If the temperature is lowered because of altitude, cooking time will have to be extended to complete the cooking process.
Therefore, we can conclude that the correct answer to this question is option A.

Note: As altitude increases and atmospheric pressure decreases, the boiling point of water decreases. It is important to compensate for the lower boiling point of water, thus, the cooking time must be increased. Actually, turning up the heat will not help cook food faster. It does not matter how high the cooking temperature is, water will not exceed its boiling point – unless using a pressure cooker.