Page 627 - College Physics For AP Courses

Chapter 14 | Heat and Heat Transfer Methods 615
convection: heat transfer by the macroscopic movement of fluid
emissivity: measure of how well an object radiates
greenhouse effect: warming of the Earth that is due to gases such as carbon dioxide and methane that absorb infrared radiation from the Earth’s surface and reradiate it in all directions, thus sending a fraction of it back toward the surface of the Earth
heat: the spontaneous transfer of energy due to a temperature difference
heat of sublimation: the energy required to change a substance from the solid phase to the vapor phase
kilocalorie:
latent heat coefficient: a physical constant equal to the amount of heat transferred for every 1 kg of a substance during the change in phase of the substance
mechanical equivalent of heat: the work needed to produce the same effects as heat transfer net rate of heat transfer by radiation: is

R factor: the ratio of thickness to the conductivity of a material
radiation: heat transfer which occurs when microwaves, infrared radiation, visible light, or other electromagnetic radiation is
emitted or absorbed
radiation: energy transferred by electromagnetic waves directly as a result of a temperature difference
rate of conductive heat transfer: rate of heat transfer from one material to another
specific heat: the amount of heat necessary to change the temperature of 1.00 kg of a substance by 1.00 oC
Stefan-Boltzmann law of radiation: where is the Stefan-Boltzmann constant, is the surface area of the object, is the absolute temperature, and is the emissivity
sublimation: the transition from the solid phase to the vapor phase thermal conductivity: the property of a material’s ability to conduct heat
Section Summary
14.1 Heat
• Heat and work are the two distinct methods of energy transfer.
• Heat is energy transferred solely due to a temperature difference.
• Any energy unit can be used for heat transfer, and the most common are kilocalorie (kcal) and joule (J).
• Kilocalorie is defined to be the energy needed to change the temperature of 1.00 kg of water between and
.
• The mechanical equivalent of this heat transfer is
14.2 Temperature Change and Heat Capacity
• The transfer of heat that leads to a change in the temperature of a body with mass is , where is the specific heat of the material. This relationship can also be considered as the definition of specific heat.
14.3 Phase Change and Latent Heat
• Most substances can exist either in solid, liquid, and gas forms, which are referred to as “phases.”
• Phase changes occur at fixed temperatures for a given substance at a given pressure, and these temperatures are called
boiling and freezing (or melting) points.
• During phase changes, heat absorbed or released is given by:
where is the latent heat coefficient.