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CHAPTER 14 Heat and Thermal Energy Sources Key Ideas • Thermal energy influences temperature, density, pressure, and a substance’s physical state. • Thermal energy can be transferred by conduction, convection, and radiation. • Most of the thermal energy at Earth’s surface comes from the Sun. • Earth’s interior has large quantities of thermal energy. 14.1 Temperature and Thermal Energy • Temperature is an indicator of the average kinetic energy of particles. • Kinetic energy is the energy that a substance has due to its motion. VOCABULARY kinetic molecular theory kinetic energy temperature thermal energy 14.1 Temperature and Thermal Energy • Temperature is commonly measured in degrees Celsius or in Kelvin. VOCABULARY kinetic molecular theory kinetic theory temperature thermal energy • When the temperature of a substance increases, its particles move faster and spread out. This causes the substance to expand and become less dense. 14.1 Temperature and Thermal Energy • Thermal energy includes both kinetic energy and potential energy from the motion of particles and their relative positions and forces of attraction. • thermal energy = (kinetic energy + potential energy) number of particles VOCABULARY kinetic molecular theory kinetic theory temperature thermal energy 14.2 Heat • Heat is defined as the transfer of thermal energy from one object to another because of differences in their temperature. • Thermal energy always moves from warmer to cooler objects. VOCABULARY heat conduction radiation convection insulators specific heat capacity latent heat 14.2 Heat • Thermal energy can be transferred by conduction, convection, and radiation. • Conduction is thermal energy transfer through direct contact of particles. • Convection is a method of thermal energy transfer resulting from the movement of particles in fluids due to density differences. • Radiation is the process by which thermal energy is transferred via electromagnetic waves, without particles touching. VOCABULARY heat conduction radiation convection insulators specific heat capacity latent heat HEAT RAP: http://www.youtube .com/watch?v=7Y3 mfAGVn1c 14.2 Heat • A substance’s specific heat capacity is a measure of the amount of energy (measured in joules) needed to raise the temperature of 1 kg of the substance by 1 °C. VOCABULARY heat conduction radiation convection insulators specific heat capacity latent heat • Latent heat is the energy needed to change a substance from one state to another without changing temperature. • Latent heat is absorbed or released during changes of state. 14.2