Successfully reported this slideshow.
We use your LinkedIn profile and activity data to personalize ads and to show you more relevant ads. You can change your ad preferences anytime.

2.1.ppt

551 views

Published on

  • Be the first to comment

  • Be the first to like this

2.1.ppt

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

×