Does water condense at 1 atmosphere and 100 degc? Can heat vaporization be equated with the heat of condensation?
Is this right? Is there a need to look at the fundamentals of intermolecular forces that control vaporization and condensation?
Background
Condensation of vapor
Condensation is the process where water vapor becomes liquid. Water vapor will only condense onto another surface when that surface is cooler than the dew point temperature. The change in density is accompanied by a release of energy when the molecules move closer together, and gas becomes a liquid. The energy released when gaseous water vapor condenses to form liquid water droplets is called latent heat. When water is in a vapor state it does not have significant intermolecular forces. Until there are enough intermolecular forces between water molecules to force them to join together, condensation does not take place.
Therefore, it is clearly emerging before water can condense, they must come closer. This can be achieved only in two ways [1] increase pressure and or [2] reduce the kinetic energy of water vapor molecules by lowering vapor temperature. If I just leave saturated water vapor at 1 atmospheric pressure at 100 degc it will not condense until either the pressure is increased or vapor temperature is reduced.
Can anyone predict how many molecules are coming close enough at every moment to condense?
How intermolecular forces work in condensation?
In the case of water as a molecule there are two types of physical forces are working
Dipole-Dipole attraction: In water H has a positive charge and O has a negative charge. These two charge centers constitute two poles on the molecule. The positive charge attracts a negative charge and this is called dipole-dipole interactions. A typical example: hydrogen bond, the attraction between a partially positively charged hydrogen in one molecule and a partially negatively charged oxygen.
London forces: The London dispersion force is a temporary attractive force that results when the electrons in two adjacent atoms occupy positions that make the atoms form temporary dipoles. This force is sometimes called an induced dipole-induced dipole attraction.
In every moment these physical bonds are breaking and forming in an unpredictable manner. Every time bonds form there is a gain in potential energy and every time these physical bonds break potential energy converts to kinetic energy. There is no law that keeps an account of many bonds are forming and breaking at every moment.
So, two things are emerging: Saturated water vapor cannot condense at 1 atmospheric pressure at 100 degc. Either you have to increase pressure or reduce vapor temperature. The second point is that even if water molecules are brought together how many molecules of water will condense and how much latent heat will be released is absolutely unknown.
Let us take a quick look at the straightforward case of water vaporization. Here at 100 degc at 1 atmospheric pressure potential energy converts to kinetic energy. Water becomes vapor. There is no ambiguity. Temperature and pressure both are measurable.
Question: Can heat vaporization be equated with the heat of condensation?