🔍 Key Concepts

• Vapor pressure definition in chemistry and hazardous materials handling • Relationship between vapor pressure and evaporation in a closed container • Difference between how fast something evaporates vs. the pressure its vapor creates

💭 Think About

• Ask yourself: When a liquid is in a sealed drum or tank, what are the vapor molecules doing above the liquid surface? • Think about what the word pressure normally means in physics (like air pressure in a tire) and apply it to vapors from a liquid. • Which choice talks about a measurable, physical quantity that can be read with a gauge or expressed in units like mmHg or kPa?

✅ Before You Answer

• Which option clearly refers to pressure (a force per unit area) rather than just speed or amount of evaporation? • Remember that vapor pressure is usually measured in mmHg (millimeters of mercury) or kPa (kilopascals)—which description best matches something that can be expressed in those units? • Distinguish between: how fast something evaporates, how much can evaporate, and the force of the vapor against the walls of a container.