Usually when we think of condensation, we think of the droplets of water that form on a cold glass on a humid day, or perhaps we think of dew making the grass wet on a summer morning, or maybe the fog that forms on the bathroom mirror after you have a hot shower. In those familiar cases of condensation, the water vapor is mixed in with dry air in a very dilute mixture. For example, at 75 deg F, 60% relative humidity, the water vapor comprises only about 1.1% of the total moist air, by mass. Even at 75 deg F, 100% relative humidity, (at which point the vapor is about to start condensing to liquid) the water vapor is only about 1.8% of the mixture. So, we’re accustomed to condensation of water from a very dilute mixture of water vapor in air. In this blog, we’ll consider the condensation of pure water vapor, and see some surprising forces.
