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Thermochemistry

Thermochemistry. q= mc D T. Specific Heat. is the amount of heat required to raise the temperature of one gram of a substance by one degree Celsius. Represented by a “ C ” Because different substances have different compositions, each substance has its own specific heat.

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Thermochemistry

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  1. Thermochemistry q=mcDT

  2. Specific Heat • is the amount of heat required to raise the temperature of one gram of a substance by one degree Celsius. • Represented by a “C” • Because different substances have different compositions, each substance has its own specific heat

  3. A low specific heat is matter that loses or gains heat quickly • Examples: • tiles on the space shuttle • concrete that we walk on

  4. A high specific heat is matter that loses or gains heat slowly • Examples: • water - has a uniquely high specific heat compared to other substances.

  5. How do we calculate the amount of heat a substance loses or gains? We use the mass, known specific heat and the change in temperature.

  6. Heat Curve Diagram Liquid boiling (vaporizing) Gas warming Temperature (°C) Solid melting Liquid warming Solid warming

  7. q = (m)(C)(DT) q = the heat absorbed or released C = specific heat of the substance m = mass of the sample in grams DT = the change in temperature DT = Tfinal – Tinitial

  8. Suppose that the temperature of a 5.00 x 103 g block of concrete sidewalk increased by 6.0 °C. How much heat did the concrete absorb? q = m = C = DT =

  9. In the construction of bridges and skyscrapers, gaps must be left between adjoining steel beams to allow for the expansion and contraction of the metal due to heating and cooling. The temperature of a sample of iron with a mass of 10.0 g is changed from 50.4 °C to 25.0 °C with the release of 114 J. What is the specific heat of iron? q = m = C = DT =

  10. If it takes 3590 calories to heat up a sample of water by 12.2 oC, what is the mass of the water? q = m = C = DT =

  11. If 5750 J of energy are added to a 455 g piece of glass at 24.0 oC, what is the final temperature of the glass? q = m = C = DT =

  12. How do food chemists obtain Calorie information that appears on our packaged food? • They use combustion reactions that they carry out in calorimeters. • Calorimeter – an insulated device used for measuring the amount of heat absorbed or released during a chemical or physical process

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