Topic: Thermal Physics PHYSICS 231schatz/PHY231/Lectures/lecture_thermal2_post.pdfunderstood the concepts and can derive equations that apply to a specific problem • Thermal energy

PHYSICS 231 Topic: Thermal Physics

Current Assignments •  Homework Set 8 open - due Thursday, Mar

24, 11pm •  Next week Thursday, March 31, midterm

exam 2. – Topics: Momentum, Circular motion, rotation,

gravity, solids and fluids – As usual:

•  No homework due during exam week •  Review lecture Tuesday before exam

– Did you start your equation sheet?

4/4/11 Physics 231 Spring 2011 2

Key Concepts – Temperature (atomic picture, kinetic energy,

scales)

– Mole, atomic mass number

– Thermal expansion of solids (linear expansion of volume and length)

–  Ideal gas law

– PV diagrams for constant V, P, or T

– Work done on gas (what does it do, calculation, and extraction from PV diagram)

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Key Equations •  Note that these are only useful once you

understood the concepts and can derive equations that apply to a specific problem

•  Thermal energy

•  Temperature (K)-energy:

•  T (in K) = TC (in 0C) + 273

•  TC=5/9 (TF – 320)

•  Be able to convert grams in moles …

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€

Eth = NKavg = N 12mvrms

2

€

Kavg =32kBT

Key Equations •  Note that these are only useful once you

understood the concepts and can derive equations that apply to a specific problem

•  Volume thermal expansion

•  Linear thermal expansion

•  Ideal gas law

•  Work done on gas (or area under P(V) curve)

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€

ΔV = βViΔT

€

ΔL = αLiΔT

€

PV = NkBT

€

W = PΔV

Simulation

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http://www.google.com/url?sa=t&source=web&cd=1&sqi=2&ved=0CBgQFjAA&url=http%3A%2F%2Fwww.colorado.edu%2Fphysics%2Fphet%2Fprojects2%2Fidealgas%2Fidealgas.jnlp&rct=j&q=ideal%20gas%20law%20demonstration&ei=D3GLTaD2EKGG0QHAu_SIDg&usg=AFQjCNEiwoEr9sbr_PbikTM9SCTMwdgZXA&sig2=jZ0U8mV-eBYYB6ZOnNrnAw

Speed and Kinetic Energy of Gas Molecules

Slide 12-17

Two containers of the same gas (ideal) have these masses and temperatures: •  Which gas has

atoms with the largest average thermal energy?

•  Which container of gas has the largest thermal energy? A.  P, Q B.  P, P C.  Q, P D.  Q, Q

Checking Understanding

Slide 11-21

Two containers of the same gas (ideal) have these masses and temperatures: •  Which gas has

atoms with the largest average thermal energy?

•  Which container of gas has the largest thermal energy? A.  P, Q B.  P, P C.  Q, P D.  Q, Q

Answer

Slide 11-22

Volume check

•  1 m3 equals:

A: 100 cm2

B: 1000 cm2

C: 10,000 cm2

D: 100,000 cm2

E: 1,000,000 cm2

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Phases of Matter

Slide 12-16

Thermal expansion

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Clicker question

•  To fit the ball through the hole does one have to: – A: Heat the ball

– B: Cool the ball

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Clicker question

•  To fit the ball through the hole one must: – A: Heat the plate with the hole

– B: Cool the plate with the hole

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Clicker question

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2 materials bonded (glued) together

Aluminum

Steel

What happens to the stick when heated: A: Stays straight, gets longer B: Stays straight, gets shorter C: Bends upward D: Bends downward E: remains unchanged

Water is different

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Quiz

•  When increasing the number of particles in the box

A: Pressure increases B: Pressure decreases

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Quiz

•  When increasing the temperature of the gas in the box

A: Pressure increases B: Pressure decreases

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Quiz

•  When increasing the volume (size) of the box while leaving the same amount of gas inside

A: Pressure increases B: Pressure decreases

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Quiz

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m

Gas

Gas pressure is A: same as outside pressure B: higher than outside pressure C: lower than outside pressure

Quiz

4/4/11 Physics 231 Spring 2011 21

m

Gas

When heated, gas pressure will A: stay the same B: increase C: decrease