Question

Why does a beaker of 40.0ºC water placed in a vacuum chamber start to boil as the chamber is evacuated (air is pumped out of the chamber)? At what pressure does the boiling begin? Would food cook any faster in such a beaker?

a) The water boils due to increased pressure; food would cook faster.

b) The water boils due to decreased pressure; food would cook faster.

c) The water freezes due to increased pressure; food would cook slower.

d) The water freezes due to decreased pressure; food would cook slower.

Answer 1

The beaker of 40.0ºC water placed in a vacuum chamber starts to boil as the chamber is evacuated because the pressure inside the chamber decreases.

The boiling point of water decreases at lower pressures. Food would not cook faster in such a beaker because the temperature of the boiling water would be lower.

Step-by-step explanation:

The beaker of 40.0ºC water placed in a vacuum chamber starts to boil as the chamber is evacuated because the pressure inside the chamber decreases.

When the pressure drops, the boiling point of water also decreases. At lower pressures, water can boil at lower temperatures. So, the water in the beaker boils due to decreased pressure, not increased pressure.

Food would not cook faster in such a beaker because the boiling point of water decreases as the pressure decreases. At lower pressures, water boils at lower temperatures, which means the temperature of the boiling water would be lower.

In cooking, higher temperatures are generally required for faster and more efficient cooking, so food would actually cook slower in a beaker with lower boiling temperature.