Abstract: The chemical thermodynamic properties of the salt, organic, and acid mixtures present in soluble aerosol particles govern the particles’ phase state, water uptake, and gas-particle partitioning, as functions of temperature and relative humidity. In this course, we will cover fundamental thermodynamic properties used to describe atmospheric aerosol particles, such as hygroscopicity and water uptake; activity coefficients and deviation from ideal behavior; solid-liquid-gas chemical partitioning; phase transitions including deliquescence, efflorescence and liquid-liquid separation; and thermodynamics of surfaces, including Kelvin effect, surface tension, surfactants and surface-bulk partitioning.  Bulk and single particle thermodynamic measurement techniques will be reviewed, including isopiestic measurement techniques, electrodynamic balances, optical tweezers, and hydrodynamic traps. Attention will be given to typical sources of error and uncertainty in the measurements, in order to improve the user’s understanding and interpretation of thermodynamic properties. Available modeling approaches and predictive calculators for thermodynamic properties of activity, surface tension, density, phase partitioning, and mixing state will be discussed.