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No electronic devices or accessories!!!

No electronic devices or accessories!!! If I see it, hear it, or even SUSPECT you are using it, I will take it and turn it in to the office. Heat Transfer. Heat Transfer. What happens when you pick up a hot skillet from the stove?. Heat Transfer. IT BURNS!. Heat Transfer.

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  1. No electronic devices or accessories!!! • If I see it, hear it, or even SUSPECT you are using it, I will take it and turn it in to the office

  2. Heat Transfer

  3. Heat Transfer What happens when you pick up a hot skillet from the stove?

  4. Heat Transfer IT BURNS!

  5. Heat Transfer Why does it “feel” hot, what is really happening?

  6. Heat Transfer Heat flows from the pan into your skin causing your skin temperature to rise uncomfortably fast.

  7. Heat Transfer Why does heat flow from the pan to your hand?

  8. Heat Transfer Heat flows naturally from the warmer object (higher energy) to the cooler one (lower energy).

  9. Heat Transfer The science of how heat flows is called heat transfer.

  10. Heat Transfer Heat flow happens whenever there is a difference in temperature.

  11. Heat Transfer Thermal equilibrium -when two objects have the same temperature

  12. Heat Transfer Thermal equilibrium -NO heat flows because the temperatures are the same

  13. Heat Transfer

  14. Heat Transfer What is Heat? (it’s not the police, remember thermal energy)

  15. Heat Transfer Heat is the flow or transfer of thermal energy

  16. Heat Transfer What is Thermal Energy?

  17. Heat Transfer Thermal Energy – the sum of all kinetic energy of the molecules of a substance

  18. Heat Transfer What two things does Thermal Energy depend on?

  19. Heat Transfer Mass and Temperature

  20. Heat Transfer There are 3 ways heat transfer takes place Conduction Convection Radiation

  21. Heat Transfer Conduction

  22. Heat Transfer Conduction is the transfer of heat through materials by the direct contact of matter.

  23. Heat Transfer If you have ever burned yourself on a hot pan, you have experienced conduction. (ouch)

  24. Heat Transfer Thermal Conductor – materials that conduct heat easily

  25. Heat Transfer The thermal conductivity of a material describes how well it conducts heat.

  26. Heat Transfer High Low

  27. Heat Transfer

  28. Heat Transfer Heat conduction works: -in solids and liquids by transferring energy through bonds between atoms or molecules. -in gasses through collisions of atoms -better in solids due to the high density of atoms and stronger bonds

  29. Heat Transfer Heat Conduction can not happen in a vacuum Conduction happens only if there are particles available to collide with one another.

  30. Heat Transfer Thermal Insulator – materials that conduct heat poorly

  31. Heat Transfer

  32. Heat Transfer Because air is a poor conductor of heat, a down jacket keeps you warm in the cold.

  33. Heat Transfer Convection

  34. Heat Transfer Convection is the transfer of heat by the motion of liquids and gases

  35. Heat Transfer

  36. Heat Transfer Convection in a gas occurs because gas expands when heated. When a gas expands, the mass is spread out over a larger volume so the density decreases. Hot gas with lower density is lighter than surrounding cooler gas and floats upward.

  37. Heat Transfer Convection in liquids also occurs because of differences in density. Hot liquid is less dense than cold liquid. If you watch the surface of a pot of boiling water, you can see the convection currents.

  38. Heat Transfer http://www.youtube.com/watch?v=WEDUtS0IMws

  39. Heat Transfer Radiation

  40. Heat Transfer Radiation is heat transfer by electromagnetic waves, including light

  41. Heat Transfer If you stand in the sun on a cold, calm day, you will feel warmth from the sun. Heat from the sun is transferred to Earth by thermal radiation.

  42. Heat Transfer Radiation can travel through a vacuum

  43. Heat Transfer All objects with a temperature above absolute zero (-273 °C) emit thermal radiation.

  44. Heat Transfer Your own body gives off thermal radiation and that is why you and all other living things “glow” when viewed with an infrared night-vision camera.

  45. Heat Transfer

  46. Heat Transfer Thermal radiation is absorbed by objects, as well as emitted.

  47. Heat Transfer

  48. Entropy • Entropy is a measure of the random activity in a system. 

  49. Affecting Entropy • Several factors affect the amount of entropy in a system • More energy put into a system excites the molecules and the amount of random activity. • As a material expands in a system, entropy increases. • More ‘party time mosh pit’ for the molecules, more entropy.

  50. Entropy tends to increase over time… Just like the entropy in your… • Bedroom • Car • Kitchen • Backpack • Closet

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