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Thermal Energy Transfers
Chapter 6 Lessons 1 and 2
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Thermal Energy and Temperature
Sum of the kinetic energy and the potential energy of the particles that make up a material Temperature Average kinetic energy of the particles that make up a material
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Thermal Energy and Temperature continued
Temperature and thermal energy are not the same! Similar kinetic energy (ice melting) Different potential energy (distance between particles)
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Heat Movement of thermal energy from a warmer object to a cooler object Heat and thermal energy are not the same. All objects have thermal energy. When you heat an object, thermal energy is transferred.
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How is thermal energy transferred?
Radiation, Conduction, Convection
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Radiation The transfer of thermal energy from one material to another by electromagnetic waves Warm objects: more radiation Can be transferred through solids, liquids, and gases Only way thermal energy can travel from Sun to Earth Space is a vacuum.
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Radiation continued How does the Sun heat the inside of a car?
Jumping Penny Demo
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Conduction Transfer of thermal energy between materials by the collision of particles (contact) Continues until all particles in contact are equal Thermal conductors A material through which thermal energy flows easily Metals Thermal insulators Material through which thermal energy does not flow easily
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Conduction continued Specific Heat
The amount of thermal energy required to increase the temperature of 1 kg of material by 1C Thermal conductors have a lower specific heat Thermal insulators have a higher specific heat Water has a high specific heat Prevents body from overheating Used to cool machinery Pools, oceans, lakes cool in summer
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Thermal Expansion and Contraction
An increase in a material’s volume when its temperature increases Particles speed up and move farther apart Thermal Contraction A decrease in a material’s volume when its temperature decreases Particles slow down and move closer together Most noticeable in gases, less in liquids, and least in solids
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Thermal Expansion and Contraction continued
Sidewalk Gaps Too much expansion causes cracks Control joints cut for cracks Hot Air Balloons Thermal Expansion – to rise Thermal Contraction – to land Ovenproof Glass Expands less than ordinary glass
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Convection Warm liquid moves from one place to another, which transfers thermal energy Only occurs in fluids (water, air, magma, syrup)
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Density, Thermal Expansion, Thermal Contraction
Heating water: Burner transfers thermal energy to the container Thermal expansion in water in the bottom makes it less dense Water surface transfers thermal energy to air Water on surface cools and contracts Dense water sinks to the bottom Less dense water rises Cycle continues
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Convection Currents in Earth’s Atmosphere
Convection Current: movement of fluids in a cycle because of convection Circulates water on Earth, air in a room, materials in Earth’s interior, Moves matter and thermal energy from inside the Sun to its surface Move air between the equator and latitudes 30N and 30S Earth’s climates Sun’s thermal energy is concentrated in this area Heat moves from warmer objects to cooler objects
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