Physics I Unit Outline: Thermodynamics

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Oct 28, 2013 (3 years and 11 months ago)

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Physics I
Unit Outline:

Thermodynamics


Time Frame:


9

days

Textbook Chapters:

17
-

24

Labs:



Learning
Targets
:


1

I can explain the concepts of heat, pressure, and temperature in terms of the
kinetic model.

2

I can explain the first and second laws of Thermodynamics and use them to
explain the operation of a heat engine.

3

I can describe and identify examples of conduction, convection, and
radiation.

4

I can calculate the amount of heat transferred to or from an object when its
temperature changes.


Important Terms:


Energy

Fahrenheit

Specific heat

Power

Celsius

C
alorimeter

Joule

Kelvin

Phase change

Watt

Absolute zero

Thermal Expansion

Calorie

Thermal equilibrium

Entropy

Heat (thermal energy)

Conduction

Internal Energy

Temperature

Convection

Heat Engine

Kinetic model

Radiation

Refrigerator


2

Unit Calendar


Dates

Day

Topic

Assignment
s

1/31

Th

Thermodynamics Exploration Lab



2/1

F

Heat and
Temperature (scales)

Pressure

Kinetic Model


Thermodynamics 1

2/4

M

1
st

and 2
nd

Laws of Thermodynamics

Heat Engines

Efficiency


Thermodynamics 2

2/5

T

Quiz: Heat & Temperature



2/6

W

Heat Transfer and Thermal Equilibrium


Methods of Heat Transfer


Heat

Transfer I

2/7

Th

Amount of Heat Transferred

Specific Heat



2/8

F

Calculating heat gained and lost


Heat Transfer II

2/11

M

Quiz: Heat Transfer




2/14

T

Review


Thermodynamics Review

2/15

W

Early Release Day


Heat Created in dropping ball lab




Thermodynamics Test




3

Thermodynamics I


Heat and Temperature

Physics I


1
. List the four assumptions we made in developing the kinetic model
. Why do we use the kinetic
model?





2. In terms of the kinetic model (like discussed in class), define
heat. What are the units of heat?





3. What is temperature? What are possible units for temperature? How does the temperature of
an object relate to the amount of heat that object possesses?




4. Describe, in terms of the energies of the individual

molecules, what happens when an object
gains heat.





5. What was the original unit for thermal energy? How was the unit defined and how is it used
today?





6. What is absolute zero?





7. What is the temperature of
empty space
?





8
. Is heat
kinetic energy or potential energy? Explain.





9. Define the term pressure. Explain how a gas exerts pressure on its container using the kinetic
model.





10. A container holds 1 L of an ideal gas. Describe three ways that the pressure of the gas
can
be increased.

4

Thermodynamics II
-

Laws of Thermodynamics

Physics I


1. Describe in general how heat can be used to do work. Draw a simple diagram of a heat
engine.




2. Why must the operating temperature of a heat engine be higher than that of the

cold sink?




3. What is the one factor that affects the ideal efficiency of a heat engine? Why can the efficiency
of a heat engine never
reach

100 %?




4. What factors affect the efficiency of a real heat engine?





5. Describe the 2
nd

Law of Thermo
dynamics and list 4 consequences of it.




6. Why will all of the energy in the universe eventually be heat?




7. Gerald drops a .5 kg basketball from a height of 2 m on to the gym floor. The basketball
bounces, but does not reach a height of 2 m. As
the ball continues to bounce, the ball reaches a
lower height each time until it finally doesn’t bounce anymore.


a) Describe the energy transformations of the ball after it is released and it bounces.




b) According to Conservation of Energy, a warm bask
etball at rest on the floor could have the
thermal energy transformed into kinetic energy and move upwards. Explain why this has never
been observed in real life.




c) How much heat is created in this process?




8. A cylinder holds 1 L of an ideal gas
at room temperature. 800 J of heat is added to the gas.
Calculate how much heat is absorbed by the gas when:


a) the gas does no work on its surroundings


b) the gas does 200 J of work on its surroundings


c)
c
alculate the efficiency of the cylinder if 2
00 J of work is done on the surroundings.

5

Heat Transfer

I


Methods of Heat Transfer

Physics I


1. Using your previous knowledge about heat, why is heat transferred between objects?






2. What is necessary for the net flow of heat between objects to

be zero?






3. Describe how 2 objects in direct contact with each other transfer heat. Draw a diagram
illustrating on the microscopic level.






3. There are 3 methods of heat transfer. Name each one, describe how it works, where it works,
and draw

a sketch showing how it works. Then describe a specific example for each.


a) __________________________









b) __________________________










c) __________________________



6

4. For each example, determine the heat transfer method being used


a) You heat your bacon by setting it in a hot skillet



b) The hood of your car heats up while sitting under the sun



c) The hood of your car heats up while in the garage because the car’s engine is hot



d) Heat from an underwater volcano causes the
water at the surface to boil



e) a pot gets hot while sitting on a stove



f
)
Broccoli floating in a
pot

of water

on an electric stove is heated



g
) Rising hot air causes turbulence in an airplane



h
) A thermometer placed in the sun reads 100 °F



i
) A
thermometer in the shade reads 85 °F



j) The ground heats up during the day



k) A fireman touches a door knob to see if there is fire on the other side.



l) A steak is cooked underneath a broiler



m
) A pig is roasted over an open flame



n) A snake c
an sense a warm mouse against the cold ground



5. Using your knowledge of heat transfer, explain how a greenhouse lets heat in to warm plants
but doesn’t allow it out.








6. Which method of heat transfer to you think is most efficient? Explain why.

7

Heat Transfer

II


Amount of Heat Transfered

Physics I


1. 2500 J of heat is added to a .5 kg metal sample. The metal has a specific heat of 250 J∙kg/°C.
By how much will the temperature change?








2. 75000 J of heat is added to a 2 kg metal samp
le. The metal has a specific heat of 250
J∙kg/°C. If the initial temperature of the metal is 15 °C, what will its final temperature be?








3. A student heats a 2.5 kg sample of a new alloy from an initial temperature of 12 °C to a final
temperature of 30 °C. During this time, the alloy absorbs 54,000 J of heat. Calculate the specific
heat of the new alloy.








4. An engine made of 12
.8 kg of aluminum is heated from 15 °C to its operating temperature of
100 °C. How much heat did it absorb?








5. A student wishes to melt some copper to create a new statue of her physics teacher. She has
a butane tank that is capable of releasing
850,000 J of heat. What is the maximum mass of
copper she can heat from 8 °C to 1085 °C?








8

6. A hot tub holds 480 kg of water. On a cold day, the initial temperature of the water is 4 °C.
Before getting in, the hot tub water needs to reach a temp
erature of 50.0 °C.


a) How much heat is needed to warm up the hot tub water?







b) The hot tub is heated by a propane heater. When burned, propane releases 4.65 x 10
7

Joules
of heat energy per kilogram of propane. How much propane must be burned to heat the hot tub
water?







c) Taking the price of propane to be $0.81 per kilogram, how much will it cost to heat the hot tub?







7. A race car engineer is studying
the heat absorbing properties of a new ceramic alloy he
intends to use in race car manufacturing. He
heats a 0.5 kg sample of the alloy to a temperature
of 500 °C and places it in a thermally sealed container holding 2.0 kg of water at an initial
temperat
ure of 20 °C. The water and the ceramic sample reach an equilibrium temperature of 30
°C.


a) How much heat was gained by the water?







b) How much heat was lost by the ceramic?







c) Calculate the specific heat of the ceramic.

9

Thermodynamics
Review

Physics I


1. In terms of the kinetic model, define the terms heat, temperature, and pressure. List the unit
for each.






2. List three ways in which the pressure of a gas in a container can be increased.






3. List and describe the differen
ces between the three temperature scales. Which one is the SI
temperature scale? What is absolute zero?






4. Define the 1
st

Law of Thermodynamics. What does it tell us about heat engines?






5. Write the equation for efficiency. Why can the
efficiency of any machine never be greater than
100 %? Your answer has nothing to do with friction or other resistive forces.






6. Define the 2
nd

Law of Thermodynamics and define the term
entropy
. List four consequences
of the law.







7. What fac
tors affect the efficiency of a heat engine? Why can the efficiency of a heat engine
never reach 100 %?

Your answer has nothing to do with friction or other resistive forces.






10

8. When do two objects transfer heat between them? What is the condition

called when they do
not transfer heat?







9. List and describe the three methods of heat transfer. Give a common example of each.







10. What does the term specific heat mean? What common material has the highest specific
heat?







11. List
the three factors that determine how much heat is transferred between two objects.
Write an equation for finding the amount of heat transferred between two objects.







12. A fork lift takes in 5000 J of energy from a gasoline engine when it lifts a 25

kg pallet of
shrimp from the dock floor to a storage shelf 4.0 m above the dock floor.


a) How much work is done on the pallet of shrimp?






b) How much heat does the fork lift produce?







c) What is the efficiency of the forklift?







d) How much
energy would the fork lift take in to lift a 40 kg pallet of red snapper to the same
height?






11

13. The efficiency of a gasoline engine is approximately 28 %.

a) How much
work

does the motor
do

if it burns
2800 Joules of
gasoline?






b) How m
uch heat

does the motor produce?






14. Mary uses silver to make new pieces of art for her art class. She has a sample of silver
whose mass is 1.8 kg.

a) How much energy must Mary add to raise the temperature of the silver from 12 °C to 28 °C?






b) If Mary
adds exactly 6210 J of heat to the silver, what will its temperature change be?







15. Jimmy places a 2.0 kg sample of an unknown metal in an oven to heat it to 100 °C. He
places this sample into a calorimeter containing 5.0 kg of liquid water at a te
mperature of 15 °C.
A few minutes later, he measures the equilibrium temperature of the water to be 30 °C.


a) How much heat did the water gain?






b) What is the specific heat of the metal?