What happens to the boiling point of water as the pressure decreases?

• A. The boiling point increases
• B. The boiling point remains the same
• C. The boiling point decreases
• D. The boiling point fluctuates

Answer: (C)

As pressure decreases, the boiling point of water decreases as well. This phenomenon occurs due to the relationship between vapor pressure and boiling point; when the pressure surrounding a liquid is lowered, the vapor pressure needed for the liquid to boil is achieved at a lower temperature.

In practical terms, at high altitudes, for instance, where atmospheric pressure is lower, water boils at temperatures below the standard 100 degrees Celsius (at sea level). This is why cooking times may increase or recipes may require adjustments at higher elevations, as boiling water will not reach the same temperature as it does at sea level.

Thus, given the principles of thermodynamics and the behavior of liquids under varying pressures, it's clear that the boiling point of water decreases when the pressure is reduced, confirming why this option is the correct choice.