What vapor pressure level is required for vaporization to occur?

• A. Greater than the atmospheric pressure
• B. Less than the atmospheric pressure
• C. Greater than the specific gravity
• D. Depends on the amount of thermal energy being applied

Answer: (A)

Vaporization happens when the liquid’s vapor pressure exceeds the pressure surrounding it. As you heat a liquid, molecules escape into the gas phase and build up vapor pressure. When that pressure becomes greater than the atmospheric pressure, bubbles form within the liquid and boiling begins. If the vapor pressure only reaches the atmospheric pressure, you’ve reached the boiling point; pushing it above that point leads to more vigorous boiling. Specific gravity doesn’t set this threshold, and while applying more heat increases vapor pressure, the key condition for vaporization is surpassing the ambient pressure.