What does "vapour pressure" indicate about a chemical?

Vapor pressure is a critical concept in understanding the behavior of chemicals, particularly when assessing their volatility. It is defined as the pressure exerted by a vapor in equilibrium with its liquid form at a given temperature. This means that in a closed system, if you have a liquid, some of it will evaporate and enter the gas phase, and eventually, a dynamic equilibrium will be established where the rate of evaporation equals the rate of condensation.

The importance of vapor pressure lies in its ability to indicate how readily a substance will vaporize, which is a key factor in processes such as evaporation, boiling, and the potential for the chemical to form harmful vapors in the event of a spill or leak. High vapor pressure indicates that the substance will easily transition from liquid to vapor, while low vapor pressure suggests a more stable liquid state. Understanding vapor pressure is essential for safe handling and storage of chemicals, especially those that are volatile or flammable.