Unit 28 - Heat And Temperature

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Heat and Temperature

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Unit 28 - Heat And Temperature

  1. 1. Heat and Temperature<br />Unit 28<br />
  2. 2. Temperature<br />Temperature is a measure of the average Kinetic Energy of the particles in a substance.<br />Remember KE is the energy of motion.<br />The higher the average Kinetic Energy, the faster the particles move<br />Temperature and Heat are NOT the same thing<br />View these sites for more on temperature<br />Temperature and Temperature Scales<br />Temperature<br />
  3. 3. Temperature Scales<br />There are 3 Types of Temperature Scales<br />Fahrenheit<br />Celsius<br />Kelvin<br />Celsius Fahrenheit<br />
  4. 4. Fahrenheit Scale<br />Most commonly used in United States. (originated in Great Britain)<br />Non-metric system scale<br />Not usually used in science<br />Visit these “cool” web sites<br />Converting between oF and oC<br />Fahrenheit and Celsius Scales<br />History of Fahrenheit Scale<br />
  5. 5. How Fahrenheit Works<br />Water freezes at 32°F<br />Water boils at 212°F<br />Zero was based on the lowest they could get water to stay liquid at the time <br /> (with salt in it).<br />100° was based on the highest it was believed humans could survive at the time<br />
  6. 6. Celsius Scale<br />Based on Metric System Scale<br />Most used in the world, including Canada, Europe, and Asia<br />Visit these “cool” web sites<br />History of Celsius Scale<br />Converting between oF and oC<br />Anders Celsius<br />
  7. 7. How Celsius Works<br />Water freezes at 0°C<br />Water boils at 100°F<br />Absolute zero is -273°C<br />
  8. 8. Kelvin Scale<br />Actual Metric System scale.<br />Most often used in Laboratory settings for calculation purposes.<br />There are no negative temperatures.<br />A change (Δ) of 1oC = 1 K.<br />Converting from oC to K<br />William Thomson<br />Baron of Kelvin<br />
  9. 9. Absolute Zero<br />Defined as 0 Kelvin.<br />Average temperature of space is 2.7K<br />Scientists have gotten within fractions of absolute zero, but it is impossible to ever completely stop the movement of an atom, since that means it has zero energy.<br />Boomerang Nebula contains the coldest known temperature in the universe at 1K<br />Helium can only become a gas at below 5K<br />
  10. 10. Temperature Scale Comparisons<br />373 K = 100°C<br />37°C = 99°F<br />298 K = 25°C<br />273 K = 0°C<br />-40°C = -40°F<br />0 K = -273°C<br />
  11. 11. Heat Transfer<br />Conduction, Convection, and Radiation<br />
  12. 12. Types of Heat Transfer<br />
  13. 13. Conduction<br />Takes place between solids or solids with liquids<br />Particles vibrating or moving faster transfer some of their energy to nearby atoms<br />
  14. 14. Conduction<br />When particles collide and the faster ones pass some of their energy on to the cooler ones.<br />This results in a change in energy for each particle<br />This causes the faster ones to slow down and cool <br />The slower ones speed up and heat up<br />
  15. 15. Examples of Conduction<br />Conduction requires direct contact<br />
  16. 16. Convection<br />Occurs in Fluids (liquids and gases)<br />Caused by a change in density due to a change in temperature.<br />
  17. 17. Convection con’t<br />The warmer fluid expands, becomes less dense and rises.<br />The cooler fluid contracts, becomes more dense and sinks.<br />
  18. 18. Convection con’t<br />Lava Lamps are an example of convection that you have probably seen before.<br />
  19. 19. Importance of Convection<br />Convection causes warm water vapor to rise, condense into clouds when it cools, <br />and then falls back as rain<br />Without convection, there would be no rainfall and thus no plants<br />
  20. 20. Examples of Convection<br />Magma in the mantle rises due to convection.<br />The heat from the core heats it and then it rises to form volcanoes on the surface<br />
  21. 21. Radiation<br />The transfer of energy due to Infrared and other electromagnetic rays.<br />Radiation can travel through space.<br />All things radiate heat.<br />
  22. 22. Why are light bulbs hot?<br />They produce infrared radiation in addition to visible light<br />Infrared transfers energy to the molecules that makes them vibrate faster (thus hotter)<br />
  23. 23. Thermal Expansion<br />When objects heat up their particles move faster, hit others harder, and bounce further, creating more empty space between the particles.<br />As a result, the entire substance expands.<br />This is known as thermal expansion<br />
  24. 24. Examples of Thermal Expansion<br />Roads crack as they expand in the heat<br />On bridges and other sensitive sections, expansion panels allow it to flex.<br />
  25. 25. Thermal Expansion continued<br />The liquid in a thermometer expands as it warms.<br />This causes it to head up the tube and tell you the temperature<br />
  26. 26. Heat Transfer<br />Heat Conductors<br />Good thermal conductors transfer heat rapidly<br />Metals are good thermal conductors<br />Radiators are metals that transfer the heat in the water to the air<br />Frying pans transfer heat from the stove to the food<br />
  27. 27. Heat Transfer<br />Thermal Insulators<br />Poor thermal conductors of heat.<br />Asbestos, cork, ceramic, cardboard, and fiberglass are examples of thermal insulators<br />

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