Heat

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Heat

  1. 1. Kinetic Molecular Theory •All matter is made of molecules •These are always in motion •Their motion is directly related to temperature. •Demo
  2. 2. Heat Defined•Heat is a form of energy•It is caused by the motion ofmolecules•Give credit to: Count Rumford(aka: Benjamin Thompson)•Heat is a kinetic energy
  3. 3. Heat Transfer• Heat moves from hot to cold.• It can do this through: – Conduction – Convection – Radiation
  4. 4. Conduction When there is direct contact between objects and heat is transferred.
  5. 5. Convection When there is transfer of heat in fluids The hot fluid rises, due to its lower density
  6. 6. Convection Cells
  7. 7. Radiation When heat moves as an electromagnetic wave
  8. 8. Temperature Versus Heat•Temp. is a measure of theaverage velocity of themolecules•Heat is a form of energycaused by this motion
  9. 9. ..the higher the temperature, the more energy something has But…… temperature is NOT a direct measure of the amount of heat
  10. 10. Measuring heat• Heat is measured in calories• A calorie is 4.19 joules• A calorie is how much heat is needed to get one gram of water to go up one degree Celsius.
  11. 11. Think about this…• You have a swimming pool that is 10º C• You have a cup of hot cocoa• Which has a higher temperature?• Which has more heat?
  12. 12. Temperature Versus Heat• Heat= total energy• Temperature= average energy
  13. 13. Temperature Scales• Fahrenheit• Celsius• Kelvin• linkAb zeroBases
  14. 14. Specific heat• An indicator of how hard/easy it is to get a substance to go up or down in temperature
  15. 15. Specific Heat• The amount of heat needed to raise 1 gram of a substance by 1° C• Unit= cal / g° C• Water is easy, it is:1 cal / g° C
  16. 16. Calorimeter• A device to measure heat• All you do is measure water and see how much it goes up in temperature
  17. 17. Calorimeter•The heat lost by an object is gained by the water in the calorimeter• Equation for Heat lost or gained: =Mass x ΔT x specific heat

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