Why does condensation release energy

Authors Authors and affiliations Prem Datt. Reference work entry First Online: 26 August How to cite. Armstrong, R. Cambridge: Cambridge University Press. ISBN Google Scholar. As temperature decreases, the kinetic energy is dissipated in heat. Eventually, the intermolecular bonds are strong enough to change the state of the water vapor to liquid. When a substance transforms from liquid to gas, it requires energy equal to the enthalpy of vaporization. In order to reverse this process, the system will give off that much energy.

Water's enthalpy of vaporization is roughly 44 kilojoules per mole at 25 degrees Celsius. This means that each mole of water requires 44 kilojoules in order to convert to vapor at 25 degrees Celsius.

This is also the amount of energy that water will give off when it condenses at that temperature. Water vapor needs a physical site for condensation to occur. Individual molecules of water vapor will not condense without sufficiently large particles to which they can attach. In order to provide a site for condensation, the air must be saturated with water vapor and it must have larger particles in it. Make sure that you understand that evaporation of water results in cooling of the surrounding environment and that condensation of water results in warming the surrounding environment.

The last several points are made again in this WORD document on phase changes of water in the atmosphere. I suggest that you read that document.

This is so important that it is worth repeating again! Please do not leave this page and miss these important points! Water must absorb energy to move from a lower to higher energy phase, i. In each case, the energy absorbed by water is used to change its internal molecular bonding structure.

The water must absorb this energy from outside, which often results in a cooling of the surrounding environment since it must supply the energy to the water. Water must release energy to move from a higher to lower energy phase, i. In each case, the energy released by the water results in a change in the internal molecular bonding structure. This released energy is taken up or absorbed by the surrounding environment, which typically results in a warming of the surrounding environment since it has to absorb the energy.

The water cycle refers the continuous movement of water on, above, and below the surface of the Earth. Water can change phase among liquid, gas water vapor , and solid ice at various places in the cycle. The importance of the water cycle for life on land cannot be overstated You should be familar with the basics of the water cycle and the use of the terms evaporation, condensation, precipitation, and evapotranspiration as described in the next paragraph.

Energy from the sun drives the water cycle. Remember energy must be added to liquid water absorbed by liquid water to cause it to evaporate. Liquid water on or slightly below the Earth's surface evaporates into the air, becoming the gas water vapor. Water is also evaporated from the land surface out of soils or transpired by plants. These processes on land are often lumped together and called evapotranspiration.

Thus, the dominant process near the Earth's surface is evaporation liquid to gas , acts to remove energy from the Earth's surface. This energy does not just disappear, though. The energy is now contained or stored in the water vapor molecules, which have more internal energy than liquid water molecules. Rising air currents carry water vapor up into the atmosphere, which cools the air, causing the water vapor to condense into tiny droplets of liquid water or tiny ice crystals , forming clouds.

Once at this temperature, the ice begins to melt until all the entire sample has melted, absorbing a total of Once all the ice has melted, the temperature of the liquid water rises, absorbing heat at a new constant rate of 1. When all the liquid has become steam, the temperature rises again, absorbing heat at a rate of 0.

Heating and Phase Changes of Water : A graph of temperature versus energy added. The system is constructed so that no vapor evaporates while ice warms to become liquid water, and so that, when vaporization occurs, the vapor remains in of the system. A phase change we have neglected to mention thus far is sublimation, the transition of solid directly into vapor. The opposite case, where vapor transitions directly into a solid, is called deposition.

Sublimation has its own latent heat L s and can be used in the same way as L v and L f. Privacy Policy. Skip to main content. Heat and Heat Transfer.