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2.1.ppt Presentation Transcript

  • 1. Energy
    • 2.1
  • 2. Energy and Change
    • Energy is the capacity to do work.
    • Energy is always involved when there is a change in matter.
  • 3. All physical and chemical changes involve a change in energy.
    • Sometimes energy must be supplied for the change in matter to occur.
    • For ice to melt, energy must be supplied so that the particles can move past one another.
    • Some changes in matter release energy.
    • The explosion that occurs when hydrogen and oxygen react to form water is a release of energy.
  • 4. Endothermic Processes
    • Any change in matter in which energy is absorbed is endothermic process.
    • “ feels cold”
  • 5. Exothermic Processes
    • Any change in matter in which energy is released is exothermic .
    • “ feels hot”
  • 6.
    • The law of conservation of energy states that during any physical or chemical change, the total quantity of energy remains constant.
    • You may have heard it like this: Energy cannot be created or destroyed.
    • Energy is often transferred back and forth.
    • The total energy of the systems remains the same.
    Law of Conservation of Energy
  • 7. Energy Can Be Transferred in Different Forms
    • Energy exists in different forms:
    • chemical
    • mechanical
    • light
    • heat
    • electrical
    • sound
  • 8. Heat
    • Heat is the energy transferred between objects that are at different temperatures.
    • Heat energy is always transferred from a warmer object to a cooler object.
  • 9. Heat Is Different from Temperature
    • Temperature indicates how hot or cold something is.
    • Scientists define temperature as a measurement of the average kinetic energy of particles in a substance.
    • The transfer of energy as heat can be measured by calculating changes in temperature.
  • 10. Temperature Is Expressed Using Different Scales
    • Thermometers are usually marked with the Fahrenheit or Celsius.
    • A third temperature scale, uses the unit Kelvin, K.
    • Zero on the Celsius scale is the freezing point of water.
    • Zero on the Kelvin scale is absolute zero, the temperature at which the minimum average kinetic energies of all particles occur.
    • Everything stops moving, even electrons.
  • 11. C to K & K to C
    • Use the following equations to convert between Celsius and Kelvin:
    • °C = K − 273
    • K = °C + 273
  • 12. Temperature Scales
  • 13. Heating Curve for Water SEE PAGE 44
  • 14. Heat
    • The SI unit for energy is the joule (J).
    • Specific heat is expressed in joules per gram kelvin (J/g•K).
    • Metals tend to have low specific heats.
    • Water has an extremely high specific heat.