Relative humidity indicates water vapor content compared to maximum saturation. Dew point is temperature at which air reaches 100% relative humidity. High humidity makes it feel hotter, low humidity causes respiratory issues
Originally derived by Sadi Carnot in 1824. Rediscovered by Clausius, Clapeyron, and Kelvin decades later. Kelvin and Thomson confirmed it experimentally in 1849-50
Vapor pressure is the pressure exerted by vapor in equilibrium with condensed phases. Measured in pascals (Pa) between 1 and 200 kPa. Most accurate near boiling point, less accurate below 1kPa
Raoult's law states that vapor pressure of ideal mixture equals pure component's vapor pressure multiplied by mole fraction. Law applies to ideal solutions where intermolecular forces between unlike and similar molecules are equal. More similar components approach Raoult's law more closely
Each gas in a mixture has a partial pressure as if occupying its own volume. Total pressure of ideal gas mixture equals sum of partial pressures (Dalton's Law). Partial pressure measures thermodynamic activity of gas molecules. Gases dissolve and react according to partial pressures, not concentrations
Intensive properties don't depend on system size, extensive properties do. Mass is actual mass, molar mass is mass per mole. Specific gravity is ratio of fluid density to water density at 4°C. Specific weight is intensive property, not extensive