Relationship between sensible heat and latent heat.

Figure 2-9.—Relationship between sensible heat and latent heat. sensible heat and latent heat, we are talking about The energy price is repaid, so to speak, when the two different kinds of effects that can be produced by heat, but not about two different types of heat. As previously discussed, the three basic physical states of all matter are solid, liquid, and gas (or vapor). The physical state of a substance is closely related to the distance between molecules. As a general rule, the molecules are closest together in solids, farther apart in liquids, and farthest apart in gases. When heat flow to a substance is not reflected in a temperature increase in that substance, the energy is being used to increase the distance between the molecules of the substance and to change it from a solid to a liquid or from a liquid to a gas. You might say that latent heat is the energy price that must be paid for a change of state from solid to liquid or from liquid to gas. The energy is not lost. It is stored in the substance as internal energy. substance changes back from gas to liquid or from liquid to solid, since heat flows from the substance during these changes of state. Figure 2-9 shows the relationship between sensible heat and latent heat for water at atmospheric pressure. The same kind of chart could be drawn for other substances; however, different amounts of thermal energy would be involved in the changes of state for each substance. If we start with 1 pound of ice at 0°F, we must add 16 Btu to raise the temperature of the ice to 32°F. We call this adding sensible heat. To change the pound of ice at 32°F to a pound of water at 32°F, we must add 144 Btu (the LATENT HEAT OF FUSION). No change in temperature will occur while the ice is melting. After all the ice has 2-13