What are the processes of evaporation and condensation?

Answer 1

Condensation is the process by which a gas changes its state to become a liquid. Evaporation is process by which a substance changes from its liquid state to its gas state by random particle movement.

Answer 2

The same question might be asked of any number of elements, but as for 'water':

1) The "conversion of different forms of water..." should be restated as "changes of state of water".

2) When water in it's 'gaseous or Vapor state' changes to liquid, it has changed it's 'state' from a 'vapor' to a 'liquid' through the process of 'condensation' via removal of 'HEAT' or 'increase' of 'ambient' pressure, or both. The key is the relationship between temperature and pressure. Temperature may be defined as the degree of heat content or a lack thereof, of a body or environment. This concept is related to the flow of heat from one object or region of space to another. Heat is said to "flow" or transfer from a warmer 'body' to a 'colder' one, or put another way, heat always flows from hot to cold. It is also said in thermodynamics that 'cold' is an absense of 'heat'. i.e; HOT >>>> COLD, never COLD >>>> HOT. Therefore, 'cold' is a relative term denoting an objects lack of heat as referenced by some scale. 'Heat' is a term that refers directly to the state of energy of the molecules within the body under discussion. When the molecules within a substance are energetic, that substance is said to be hot, and as that substance releases it's heat energy to another substance or body, it 'loses' heat energy and it's molecules 'slow down' or become less energetic, and the body or substance is said to be getting 'colder'.

So ...

As water 'vapor' loses energy (or cools), it 'condenses' to a 'liquid', and has thus changed 'state'. It must first reduce it's temperature through the loss of sensible heat, which will affect it's temperature (downward), then it must give up it's latent heat, which does not affect it's temperature, but instead causes it to change it's 'state' to a liquid. This loss of heat (both sensible and latent), is measured in 'BTU' (british thermal units). 1 btu is the amount of heat required to raise or lower the temperature of 1 pound of water 1 degree Fahrenheit. (Water vapor can also gain energy in the form of heat and become a 'superheated vapor'). Evaporation of course is simply the opposite of condensation, in that water gains sensible heat through some process, until it's temperature becomes 212 degrees Fahrenheit at atmosphetic pressure (called 1 atmosphere). If it continues to gain heat it's temperature will remain the same until it gains sufficient btu's (in latent heat) and then it changes state to a vapor. We generally refer to this as a boil, but a boil is simply a rapid evaporation due to the quantity of heat gained over a specific period of time.

So...

As liquid water loses heat quantity, it first loses sensible heat and it's temperature decreases (it cools), until it's temperature reaches 32 degrees at 1 atmosphere, it then must give up additional heat called latent heat where it's temperature remains constant as it continues to lose heat quantity, measured in btu's (the amount of heat in btu's that it must lose is determined by how many pounds of water there are). Above we discussed 1 btu = heat required to raise or lower 1 pound of water 1 degree Fahrenheit. When that water has lost sufficient heat energy it will 'freeze' or become a solid. It has again changed it's state. This time from a liquid to a solid. That which we call ice.

And when 'ice' gains sufficient heat energy, it 'melts', or changes state through the process of gaining sufficient sensible and latent heat energy, and once again becomes water.

Keep in mind that in this discussion we assume that we are at the surface of the earth under a pressure of 1 atmosphere, or 1 psia = 0 psig. When the pressure acting upon a substance or body changes, it has a direct and fundamental affect on the temperature at which these processes take place.

There is one more process called 'sublimation', where the change of state occurs very rapidly due to the quantity of heat gain or loss, and the change of state essentially skips a step, or two. It is in fact possible for water to change state from 'ice' to 'vapor' without becoming a liquid. That discussion however would take much too long for this forum, and so must wait until another time.

Answer 3

Condensation and evaporation involve losing or gaining liquid. freezing and melting involve turning the substance into a solid or into a liquid.