Laws, heat and expansion 2013


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Laws, heat and expansion 2013

  1. 1. Laws and Specific Heat February 18, 2014
  2. 2. Objectives 1. State the three law of thermodynamics 2. Describe how Specific Heat capacity affects our earth’s climate 3. Understand Thermal Expansion in terms of how ice and water react
  3. 3. Laws of Thermodynamics 1. First law states: a. When heat flows in or out of a system it is being neither created or destroyed b. It only transfers to a different place
  4. 4. Laws of Thermodynamics 2. Second Law states: a. Heat flows from a hot to a cold substance b. Has to be forced to move the opposite direction
  5. 5. Laws of Thermodynamics 3. Third Law states: a. No system can reach zero absolute What is absolute zero? How do we know where it is at if we can’t reach it?
  6. 6. HEAT 1. Heat is thermal energy in motion 2. Heat is measured = Joules/ Calories
  7. 7. Specific Heat Capacity 3. Different substance = different capacities for storing thermal energy a. Require different amounts of thermal energy to raise temperature
  8. 8. Specific Heat Capacity 4. Specific Heat Capacity: quantity of heat required to change the temperature of a unit mass by 1 degree a. Measure of thermal inertia b. Matters ability to resist a in temperature change
  9. 9. Higher specific heat – stronger ability to resist change Lower specific heat – low ability to resist change
  10. 10. Specific Heat Capacity 5. Which has a higher specific heat capacity, water or sand? In other words which takes longer to warm in sunlight (or longer to cool at night?)
  11. 11. Specific Heat Capacity 6. Waters specific heat capacity: a. Higher capacity for storing energy b. Absorbs a great quantity of heat for small rises in temperature c. Takes much longer to cool, resistant to loosing thermal energy
  12. 12. Specific Heat Capacity d. Water’s specific heat changes the world’s climate i. Currents carry warmer water to Europe’s west coast keeping it warmer than the cool coast’s of Canada ii. Islands and peninsula’s do not have extreme temperatures
  13. 13. 7. Bermuda is close to North Carolina, but unlike North Carolina, it has a tropical climate year round. Why?
  14. 14. Thermal Expansion February 20, 2014
  15. 15. Thermal Expansion 1. Thermal expansion - when a substance expands when heated and contracts when cooled a. Different substances have different abilities to expand and contract
  16. 16. Bimetallic strips
  17. 17. Thermal expansion b. When you can’t loosen a metal lid on a glass jar, why is it that you stick it under hot water to help you out?
  18. 18. Thermal Expansion 2. Water’s Thermal expansion a. Expands when heated b. Between 0 and 4 degrees water particles contracts becoming more dense before freezing
  19. 19. Themal Expansion a. If you heat water at zero degrees it actually contracts as the ice crystals start to collapse before it will expand at 4 degrees
  20. 20. Themal Expansion 3. When solid ice forms volume increases because of the ice crystals
  21. 21. Thermal Expansion a. Since ice is less dense it floats on bodies of water b. Water at zero degrees is less dense as well and stays near the tops c. Water at four degrees is more dense and will settle at the bottom keeping organisms warm all winter