What is all of this about?

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What is all of this about?
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What is all of this about?
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Hang Glider They can catch thermals and rise
up hundreds of feet into the air without a motor
then glide back down to Earth.
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Thermal Physics

• The study of heat energy

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Heat Assignments

• Write down the Key Concepts for 16.1-3
• 477/1,3,5 478/10,11
• 495-7/1-10(with complete statements and answer
  underlined), 28-30 and FCAT prep
• Workbook pages for Ch16 (185-192)
• All of the above MUST be done in order to do lab.

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Objectives for this section

• 1. Know that temperature is directly proportional
  to the kinetic energy of a substance.
• 2. Know the temperature scales (F, C, K), their
  freezing and boiling points, and how to convert
  temperatures from one scale to another.

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Objectives, continued

• 3. F 9/5 C 32
• 4. C 5/9 (F-32)
• 5. K C 273
• 6. Heat energy travels from hot to cold.
• 7. The lower a materials specific heat is, the
  more its temperature rises when a given amount of
  energy is absorbed by a given mass. Q mc D t
  Q units joules or calories

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• 8. Define conduction, convection, and radiation
  and know examples of each
• 9. All objects radiate energy.
• 10. 1st Law of T-D states that energy is
  conserved
• 11. 2nd Law of T-D - thermal energy can flow from
  colder objects to hotter objects only if work is
  done on the system.
• 12. 3rd Law of T-D - absolute zero cannot be
  reached.

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Specific Heat, c

• The amount of heat energy that will raise the
  temperature of 1 kg of a substance by 1 K.

Substance c (J/kg K) Substance c (J/kg K) Substance c (J/kg K) Substance c (J/kg K) Substance c (J/kg K) Substance c (J/kg K) Substance c (J/kg K) Substance c (J/kg K)
Water (liq) 4186 Copper 385
Steam 1870 Iron 449
Aluminum 709 Gold 129
Specific heat is an indicator of how slowly a
substance will heat or cool. Of the above
substances, which heats at the slowest rate?
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Specific Heat formula

• Energy mass x specific heat x temp change
• QmcDt
• How much energy must be absorbed by 420 kg of
  water in a bathtub to raise its temperature from
  300 K to 310 K?
• QmcDt
• Q420kg (4186 J/kg K) (10 K)
• Q 17 581 200 J
• 1.8 x 107J or
• 1.8 x 104 kJ

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477/2 Math Practice

• How much heat (Q) is absorbed by a 750-g iron
  skillet when its temperature rises from 25oC to
  125oC? See p.476 table for specific heat for
  iron.
• m 750 g
• t 100oC
• c iron 0.449 J/goC
• Q ?

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m 750 g t 100oC c iron 0.449 J/goC Q ? Q
mcDt Q (750g) (0.449 J) (100 oC)
goC Q 34,000J Q 34 kJ

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477/4

• A jeweler heats a 10.0 g silver ring by adding
  23.5 J of heat. How much does the temperature of
  the silver increase?
• m 10.0 g Silver
• Q 23.5 J
• c silver 0.235 J/goC
• D t ?

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m 10.0 g Silver Q 23.5 J c silver 0.235
J/goC D t ? Q mcDt (divide both sides Dt
Q by mc) mc Dt 23.5 J g oC
(10.0g)(0.235J) Dt 10.0 oC
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Assignment

• 477/1,3,5

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Temperature

• The temperature of an object or substance is the
  result of the kinetic energy of the particles in
  it.
• The faster the particles are moving, the greater
  the KE, the greater the temperature of the
  substance.
• KE is directly proportional to temperature.

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Temperature scales
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Converting temperature

• From Fahrenheit to Celsius
• From Celsius to F
• From C to Kelvin K C 273
• Add these to your circle sheet

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Practice conversions

• Convert -290.0oC to F and K
• F 9/5 C 32 9/5 (-290.0) 32
• F 9 / 5 x -290 32 -490oF
• Convert -290.0 o C to K
• K C 273
• K -290.0oC 273 -17 K

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2 Metal in running car engine

• 388K
• To C
• C K - 273 388 - 273 115oC
• To F
• F 9/5C 32
• F 9/5(115oC) 32
• F 207 32
• F 239 o F

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2 110oF Air in the Desert

• Temp To C
• C 5/9(F -32)
• C 5/9(110oF-32) 5/9(78) 43.3oC
• To K
• K C 273 43.3oC 273
• K 316.3 K

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Heat Thermodynamics
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Relating heat and temperature

• Heat is thermal energy present in a substance
  that can be transferred to another substance
• Heat travels from hotter substances to colder
  substances
• Temperature is the measure of the average kinetic
  energy of the particles within a substance

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HOT
Cold
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Transfer 1

• Conduction
• Energy is transferred between particles within a
  substance or between 2 objects in contact

Solids conduct heat best. Insulators dont
conduct heat well.
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Transfer 2

• Convection - transfer of heat by movement of
  fluids with different temperatures

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Convection Current
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Transfer 3

• Radiation - transfer of energy by electromagnetic
  waves

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Infrared rays provide thermal energy to humans
for physical therapy
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Laws of Thermodynamics

• 1st Law of T-D states that energy is conserved
  during any change.
• 2nd Law of T-D - thermal energy can flow from
  colder objects to hotter objects only if work is
  done on the system.
• 3rd Law of T-D - absolute zero cannot be reached.

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Assignment

• 477/1,3,5
• 478/10,11
• 495-7/1-10,28-30, FCAT Prep
• Workbook pages 185-192
• All of the above MUST be done in order to do lab.