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Heat

Heat. Chapter 9 Thermal Energy. Kinetic and Potential Energy. Kinetic energy- energy of motion potential energy – Is the certain amount of energy that Molecules have that is ABLE to be changed to kinetic energy. *Thermal Energy.

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Heat

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  1. Heat Chapter 9 Thermal Energy

  2. Kinetic and Potential Energy • Kinetic energy- energy of motion • potential energy –Is the certain amount of energy that Molecules have that is ABLE to be changed to kinetic energy

  3. *Thermal Energy • Both the potential energy + the kinetic energy of all the molecules in an object is: Thermal Energy.

  4. What is Temperature? • Temperature-is a measure of the average movement of molecules(kinetic energy) • (You know it as “How hot or cold something is”) • Higher temperatures mean faster moving molecules in a substance

  5. Temperature Scales • Three Common Temperature Scales (units) • Fahrenheit is used mainly in the United States • Celsius is based on water’s freezing and boiling points • Kelvin, uses zero as absolute zero, the lowest temperature an object can have.

  6. Converting Temperatures • Convert Fahrenheit to Celsius C = 5/9 ( Temperature in Fahrenheit - 32) • Convert Celsius to Fahrenheit F = 9/5 ( Temperature in Celsius) + 32 • Convert Celsius to Kelvin K= Temperature in Celsius + 273 PEMDAS DOES COUNT!!!!!

  7. Thermal Expansion • When most substances are heated they expand, The amount they expand depends on the material and temperature • That means the molecules speed up and tend to move farther apart *This means things that are cooled slow down their particles, which get closer….causing it to contract or shrink

  8. Heat Transfer Chapter 9

  9. What is Heat? • Heat-A form of energy (thermal) made by the motion of molecules. • The more movement of molecules the more heat energy • Heat energy has the ability to do work

  10. Finishing Heat’s Definition • Heat: is thermal energy that is TRANSFERRED from one object to another when the objects are at different temperatures. • So there must be a difference in temperatures for heat to transfer!

  11. DO NOT WRITEHeat & States of Matter • Solids have vibrating particles, not moving freely, • add heat and the solids melt, to liquids • Liquids have less restricted moving particles • Add heat and the liquid evaporates • To the most freely moving particles of a gas • The opposite is true when you remove heat, from gas to liquid to solid *Thermometers

  12. Transferring Heat • Heat ONLY flows from warmer objects to cooler objects • Heat NEVER flows from colder objects to warmer objects • Heat transfer occurs in three ways • Conduction • Radiation • Convection

  13. Conduction • Conduction-This is the transfer of heat by direct contact… • …This is done by the contact between particles of high kinetic (moving) energy to particles of low kinetic energy • Transfer will continue until all particles have the same kinetic energy and are the same temperature • Occurs more easily in solids and liquids • Example: • Attempting to eat a hot pocket and you burn your mouth

  14. Radiation • Radiation-Transfer of energy by electromagnetic waves. • This can occur in space or through matter since it does not require particles to transfer the energy • This is how the sun’s energy reaches Earth

  15. Convection • Convection-Heat transfer that occurs in moving fluids (liquids and gases), the movement of molecules from one part of a material to another. • Hot liquids & gases rise while cold ones fall. This creates currents that carry the heat energy • Wind is caused by convection

  16. Good and Poor Conductors Conductors: material that easily transfers heat • Poor Heat Conductors • Wood • Plastic • Glass • Gases • Good Heat Conductors -Most metals

  17. Insulation • Insulation: is used to reduce the amount of heat loss by conduction • Poor Conductors are good insulators • Materials that trap air are good insulators

  18. DO NOT WRITEHeat Transfer • Used in heating systems of homes and other buildings • Used in Cooling Systems too • Heating • Fireplace-Radiation • Steam Heating-Uses all 3 • Hot Water Heating-Uses all 3 • Electrical • Solar • Cooling • *Uses evaporation to absorb heat • Air Conditioners • Refrigerators

  19. Heating an Object • Specific Heat: This is the amount of heat needed to raise the temperature of 1 kg of a substance by 1 Degree Celsius (depends on the material) • Thermal Equilibrium: This is when there is no heat movement between two things, because both objects have reached an equal amount of thermal energy.

  20. Three Laws of Thermodynamics • First Law of Thermodynamics: Aka> The Law of Conservation of Energy. The amount of energy in the universe remains constant. • Second Law of Thermodynamics: Any process will tend to increase the amount of entropy (chaos) in the universe!!!! • Third Law of Thermodynamics: As the temperature approaches absolute zero, the entropy of a system approaches its minimum.

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