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Heat. Defining Heat. Heat and Energy. Heat – the energy transferred between objects because of a difference in their temperature Transferred from high kinetic energy to low kinetic energy Energy is transferred through particle collisions Heat is not the same as temperature
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Heat Defining Heat
Heat and Energy • Heat – the energy transferred between objects because of a difference in their temperature • Transferred from high kinetic energy to low kinetic energy • Energy is transferred through particle collisions • Heat is not the same as temperature • Temperature is the measure of an object’s internal energy
Heat and Energy • Heat and energy are both measured in Joules (J) • Other units for heat include calories (cal), kilocalories, British thermal units (Btu’s), dietary Calorie, and the therm
Heat and Work • Work is the transfer of kinetic energy • Heat is the transfer of internal energy • Friction is one way to increase an objects internal energy • Total energy is still conserved • Change in potential energy + change in kinetic energy + change in internal energy = 0 • ΔPE + ΔKE + ΔU = 0 • Remember ΔKE is the same as work and ΔU is the same as heat
Thermal Conduction • Thermal conduction – the process by which energy is transferred as heat through a material between two points at different temperatures • Particles start vibrating and moving, causing collisions • Energy is transferred through collisions • Thermal conductors – transfer energy as heat rapidly • Most metals • Thermal insulators – transfer energy as heat slowly • Asbestos, cork, ceramic, cardboard, fiberglass, plastic, rubber, gases • Cooking oil is not a good conductor, but it is used to transfer energy evenly
Convection and Radiation • Convection – transfer of energy using the displacement of cold matter by hot matter • Hot air rises, cold air sinks • Radiation – energy transferred as waves • Does not involve the movement of matter • Sun, microwave ovens
Clothing and Climate • Clothing is used to maintain body temperature • Keep heat in in cold weather • Cool the body off in hot weather • Trap cool air close to the body or evaporate sweat to cool the body • Dress in layers • Traps layers of air between layers of clothes and the body • Air is a poor conductor, so energy is not transferred