Heterogeneous condensation and evaporation induced by an unsteady rarefaction wave and by the passage of a shock wave in a water‐nitrogen mixture is studied. Time resolved measurements of modal droplet radius, droplets radius, droplet
number density, pressure, and gas density are presented. Condensation on Cr2O3‐particles of about 10 nm starts at a saturation ratio of 3.4. Typical droplet radii and droplet
number densities are 1.5 μm and 1011 m−3. A shock wave with Mach number 1.36 causes full evaporation in 4 ms.