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Chp 12

Chp 12. Temperature – measures avg. kinetic energy Fahrenheit – mostly in the U.S. 32 freezing 212 boiling for water Celcius (centrigrad) – everywhere Lord Celcius used 0 as water freezing and 100 as it boiling then divided into 100 parts. Conversions o F = 9/5 o C + 32

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Chp 12

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  1. Chp 12

  2. Temperature – measures avg. kinetic energy • Fahrenheit – mostly in the U.S. • 32 freezing 212 boiling for water • Celcius (centrigrad) – everywhere • Lord Celcius used 0 as water freezing and 100 as it boiling then divided into 100 parts.

  3. Conversions • oF = 9/5 oC + 32 • Graph? Line equation?

  4. What is the celcius temperature of the room if the thermostat reads 71 oF?

  5. oF = 9/5 oC + 32 • 71 oF = 9/5( oC ) + 32 • oC =

  6. Kelvin - based on absolute zero • K = oC + 273.15 • Thermocouples and thermometers

  7. Thermal Expansion • Linear • ∆L = αLo∆T α has units of 1/Co

  8. Stress caused by expansion • Use of stress • Bimetallic strips • Holes?????

  9. Volume Expansion • ∆V = βVo∆T β has units of 1/Co • Coefficients are located on page 342

  10. If you take a 1.0 m rod of iron as well as one of aluminum and heat them up from 22oC to 100oC, how much longer will the aluminum be? • Does the density of either rod change? Why?

  11. ∆L = αLo∆T • = (12x10-6 1/oC)(1.0m)(78oC) = • =( 23x10-6 1/oC)(1.0m)(78oC) = • Density of both decrease since volume increases and mass is the same

  12. Heat – the energy that is transferred between objects at different temperatures • Internal Energy – gives rise to the heat based on the molecules KE and PE

  13. Specific Heat – heat needed to raise the temperature of a mass of a specific material • Q=cm∆T or q = sm∆T • Joule vs calorie vs food Calorie • 4.186 J = 1 cal = 1000 Cal

  14. Calorimetry • Using temperature change and the fact that the heat lost by the hot object has to equal the heat gained by the cold object. • -Qhot = Qcold

  15. Why does the temperature remain constant during a phase change?

  16. Thus the heat needed to change the phase depends on the mass of the substance as well as the specific substance. • Q=mL or q=m∆H • m is the mass and L is the latent heat (J/g or KJ/kg)

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