Thermodynamics!

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Thermodynamics!
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Heat

• Heat is the transfer of energy between two
  objects.
• It is an electromagnetic wave when in the radiant
  form otherwise the vibrations of the atoms and
  molecules transfer heat as internal energy.

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Movement of Heat

• First thing you need to remember is that there is
  NO such thing as COLD, only a lack of heat
• Temperature is the measurement of the average
  kinetic energy of the molecules of a substance
• Heat always moves from warm to cold meaning
  from something with a higher temperature to
  something with a lower temperature

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Units of Heat

• The official SI unit is the Joule (J)
• Heat calorie (cal) 4.186 J
• Kilocalorie (kcal) 4186 J
• Food Calorie (C) 4186 J
• British thermal unit (btu) 1055 J
• Therm 105,500,000 J

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Temperature and Energy

• When objects receive or lose heat their
  temperature changes and the internal energy
  changes.
• Types of Internal Energy
• A) Translational
• B) Rotational
• C) Vibrational

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Conduction

• The transfer of heat through touch (direct
  contact)

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Conduction
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Convection

• The transfer of heat through the movement of
  liquids and gases
• Ex turbulence, climate changes, wind, boiling
  water

Hot water rises, cools, and falls.
Heated air rises, cools, then falls. Air near
heater is replaced by cooler air, and the cycle
repeats.
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Convection
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Ocean Convection CurrentsThermal Image
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Ocean Convection Currents
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Radiation

• The transfer of heat through electromagnetic waves

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Calculating the Sun's Temperature What is the
Sun's temperature? (Assume the Sun's emissivity
(e) is 1.) Distance from Sun to Earth R
1.5 x 1011 m Area of sphere of radius R
4pR2 H 1000 x 4pR2 2.83 x 1026 J/s Radius
of the Sun r 6.9 x 108 m Surface area of the
Sun A 4pr2 5.98 x 1018 m2 esAT4 H s
5.67 x 10-8 SI units T H/(esA)1/4 5375
K http//sol.sci.uop.edu/jfalward/heattransfer/he
attransfer.html
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Temperature Conversions

• There are three equations for temperature
  conversions that are important to know in this
  section.
• TF 9/5 Tc 32.0
• Tc 5/9(TF - 32.0)
• TK TC 273.15

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Independent Practice

• F to C
• 50 F
• 25 F
• 88 F
• -5 F
• 0 F

• C or F to K
• 10 C
• 10 F
• 25 F
• 50 C
• 75 C

• C to F
• 27 C
• 87 C
• 2 C
• -10 C
• 12 C

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Answers

• C to F
• 27 C 80.6 F
• 87 C 188.6 F
• 2 C 35.6 F
• -10 C 14 F
• 12 C 53.6 F

• F to C
• 50 F 10 C
• 25 F -3.89 C
• 88 F 31.1 C
• -5 F -20.6 C
• 0 F -17.8 C

• C or F to K
• 10 C 283.15 K
• 10 F 260.9 K
• 25 F 269.3K
• 50 C 323.15K
• 75 C 348.15 K