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Thermal conductors

Thermal conductors. Thermal Energy. This energy results from the random movement of all the microscopic particles in a substance. Temperature has a direct link to thermal energy: More particles in a substance  more thermal energy

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Thermal conductors

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  1. Thermal conductors

  2. Thermal Energy • This energy results from the random movement of all the microscopic particles in a substance. • Temperature has a direct link to thermal energy: • More particles in a substance  more thermal energy • Higher degree of agitation  more thermal energy, and higher temp. • Definition: energy contained in a substance, which is determined by the number of particles in the substance and their temperature (or agitation) • http://www.youtube.com/watch?v=aLwaPP9cxT4

  3. Heat energy and temperature • Heat: the transfer of thermal energy between two environments with different temperatures. Heat always passes from the warmer to the cooler environment.

  4. Heat and temperature • Temperature: takes into account only the speed of the particles. • Heat: takes into account both the speed of the particles and the number of particles (their collective mass). • This video explains things very well: • http://www.youtube.com/watch?v=f1eAOygDP5s

  5. Which has more thermal energy?

  6. Thermal conductors • When two substances are heated their temperatures increase, but not at the same rate. • How slowly their temperatures increase will determine if they’re good thermal conductors or not. • When insulating a house, would you want a substance that heats and cools fast or a substance that heats and cools slowly?

  7. Specific heat capacity • This corresponds to the amount of thermal energy required to raise the temperature of one gram of a substance by one degree Celsius. Units: J/g•°C • Hot day on a beach: sand vs water.

  8. In nature: http://www.youtube.com/watch?v=NJEBfl_LKno

  9. Coastal cities vs desert

  10. Formula • Calculating the heat absorbed or released by a given substance. This quantity of thermal energy depends on the mass, the specific heat capacity and the change in temperature of the substance. • Q = mc∆T • Q = is the heat (in Joules, J) • M = mass (in grams, g) • ∆T = temperature variation (in °C)  ∆T = Tf – Ti.

  11. How much heat is absorbed when 500. g of water , Cp = 4.184 J/goC, goes from 25.0 oC to 35.0 oC?

  12. ow much heat is absorbed when 500. g of copper, Cp = 0.385 J/goC ,  goes from 25.0 oC to 35.0 oC?

  13. How much heat is released when 150. g of iron cools from 525oC to 100oC?  (Cp = 0.44 J/goC)?

  14.  A 50.0 g block of glass (Cp = 0.50 J/goC) absorbs 333 joules of heat energy.  How much does the temperature of the glass rise?

  15. The temperature of a silver coin (Cp = 0.24 J/goC)  falls by 353 oC as it releases 5,550 Joules of heat.  What is the mass of the coin?

  16. An aluminum can with a mass of 12.5 grams (Cp = .90 J/goC) absorbs 245 Joules of heat.  How much does the temperature rise?

  17. Is mercury (Cp = 0.14 J/goC) or silver (Cp = 0.24 J/goC) a better conductor of heat? Explain.

  18. The specific heat capacity of water is a whopping 4.184 J/goC. What does this really mean? Why did I place the term “whopping” into this statement?

  19. Exam problem • An electric coffeemaker uses 350,000 J of heat energy to heat a certain quantity of water. The temperature of the water rises from 16 °C to 100 °C. • What is the mass of the water in the coffeemaker?

  20. Exam problem • A beaker containing 100g of water is heated from 20 °C to 44 °C. How much heat is needed?

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