Why do liquids have a vapor pressure? Do all liquids have vapor pressures? Explain. Do solids exhibit vapor pressure? Explain. How does vapor pressure change with changing temperature? Explain.

Vapor pressure is the pressure exerted by a vapor in thermodynamic equilibrium with its condensed phases (solid or liquid) at a given temperature in a closed system. It occurs because molecules within a substance have varying levels of kinetic energy. Molecules on the surface of a liquid that have enough energy can escape the liquid phase and enter the gas phase, creating a vapor.

All liquids have vapor pressures, although they may vary significantly depending on the liquid and its temperature. In a closed container, some of the liquid's molecules will evaporate into the gas phase, while others from the gas phase will condense back into the liquid phase. When the rate of evaporation equals the rate of condensation, the system reaches an equilibrium, and the pressure exerted by the vapor in the gas phase is known as the vapor pressure.

Yes, solids can also exhibit vapor pressure, although it is usually much lower than that of liquids due to the stronger intermolecular forces in solids. This phenomenon is called sublimation, where a solid directly transitions into a gaseous state without going through the liquid phase. This process typically occurs only in specific conditions, such as low pressure or when the solid is heated.

Vapor pressure increases as temperature increases because as the temperature rises, more molecules have enough kinetic energy to escape the condensed phase (liquid or solid) and enter the gas phase. In other words, with rising temperature, the rate of evaporation increases, leading to a higher equilibrium vapor pressure. This relationship between temperature and vapor pressure can be described by the Clausius-Clapeyron equation: \[\ln{ \frac{P_2}{P_1} } = - \frac{\Delta H_{vap}}{R} ( \frac{1}{T_2} - \frac{1}{T_1} )\] Here, \(P_1\) and \(P_2\) are the vapor pressures at temperatures \(T_1\) and \(T_2\), respectively, \(\Delta H_{vap}\) is the heat of vaporization, \(R\) is the gas constant, and \(T_1\) and \(T_2\) are given in Kelvin. In summary, vapor pressure is a property exhibited by liquids and solids, and it is affected by temperature. With increasing temperature, the vapor pressure of a substance increases due to an increase in the number of molecules with enough energy to enter the gas phase.