Heat

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Heat

  1. 1. Temperature• The measure of how hot or cold something is• Specifically – how fast the particles are moving, average kinetic energy• Matter is made of atoms that are always moving, or they have kinetic energy• The more kinetic energy, the higher the temperature
  2. 2. • Measuring temperature measures the average kinetic energy of an object• Temperature is measured with a thermometer• Thermal expansion – increase in the size of a substance in response to an increase in temp (as temp increases, particles move faster, spreading out)• Because of thermal expansion, all materials can expand and shrink when temperature changes
  3. 3. • Mercury and alcohol are used in thermometers because they increase in size (expand) by constant amounts, stay liquid at high and low temperatures• Fahrenheit – Boiling pt 212° – Freezing pt 32°
  4. 4. • Celsius – Boiling pt 100° – Freezing pt 0°• Kelvin – Boiling pt 373 – Freezing pt 273• Lowest temp on Kelvin scale is 0 or absolute zero (-459°F), the temperature at which all molecules stop moving
  5. 5. • Heat – the energy transferred between objects that are at different temperatures• Thermal energy – kinetic energy of a substances atoms• Thermal energy is transferred from areas warmer to areas that are cooler until both are equal
  6. 6. Conduction – the transfer of energy, as heat, through a material (touching)
  7. 7. Conductors and Insulators• Materials that transfer heat are called thermal conductors• Materials that do not transfer heat are called thermal insulators• Examples: – Insulators: feathers, blankets, plastics – Conductors: metals• Thermal conductivity is the rate at which a material conducts heat
  8. 8. Radiation – the transfer of energy as electromagnetic waves (sun)
  9. 9. • Radiant energy from the sun heats earth• Examples: – Fire – Radiator – Electric Oven – Electric stove
  10. 10. Convection is the transfer of thermal energyby the circulation or movement of a liquid or a gas
  11. 11. • Energy transfer can not be measured directly, instead it must be calculated• Heat = joules (J)• Specific heat = (J/Kg x ° C)• Mass = Kg• Temperature = ° C• Formula to calculate heat: J = (J/Kg x ° C) x Kg x ° C
  12. 12. Review

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