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Understanding Heat

Understanding  Heat

 

Heat energy or “heat”, is transferred in 3 different ways:

Conduction: the process by which heat or electricity is directly transmitted through a substance when there is a difference of temperature or of electrical potential between adjoining regions, without movement of the material. Different materials conduct heat at different rates – metals are very good conductors while wood and plastic not so much.

Convection: the movement caused within a fluid by the tendency of hotter and therefore less dense material to rise, and colder, denser material to sink under the influence of gravity, which consequently results in transfer of heat.

Radiant: energy which is transmitted by electromagnetic waves. The sunshine warning you while sunbathing is radiant heat. The heat from a fire is radiant heat.

Heat always goes from higher energy to lower energy. (hot to cold)

Sensible heat: is the name for energy in the form of heat that brings about either the increase or a decrease in temperature of a substance with no phase change.

Latent Heat:  The quantity of heat absorbed or released by a substance undergoing a change of state, such as ice changing to water or water to steam, at constant temperature and pressure. The heat that causes these changes is called latent heat. Latent heat however, does not affect the temperature of a substance – for example water remains at 212° F while boiling. The energy (in the form of heat) added to turn liquid water to water vapor is latent heat. This energy remains in the water vapor until it is removed and is then condensed back into liquid water. Heat that caused causes a change of state with no change of temperature is called latent heat

Some fun physics:

1 Lb. of liquid water @ 32° F takes 180 BTU to get to 212° F liquid water.

1 Lb. of liquid water @ 212° F takes 970 BTU t get to 212° F water vapor.

The water vapor will retain this energy until it is released and the water vapor condenses into  liquid water. This energy is latent heat

 

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