involve a transfer of heat, even though the temperature of the substance undergoing the phase change stays constant. The heat flow from one object to another can change either the average
supplied goes into breaking the bonds between the molecules, while the kinetic energy of the molecules remains unchanged. Gradually, more and more molecules gain sufficient energy to overcome the inter molecular forces binding the molecules one to the other. A similar phenomenon occurs when ice melts.
Heat added or subtracted for a phase change = Latent heat x Mass
If liquid water at 100 o C is changed into steam, the heat added (the latent heat of vaporization) is 540 calories for every gram of water. If steam at 100 o C is changed into water at 100 o C, 540 calories for every gram of steam must be subtracted. If ice at 0 o C is changed into liquid water at 0 o C, the heat added (the latent heat of melting) is 80 calories for every gram of ice. If liquid water at 0 o C is change into ice at 0 o C, 80 calories for every gram of liquid water must be subtracted.
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