INTRO TO PHYSICS
THERMAL ENERGY UNIT
(Ch. 21.1-21.7, 22.1-22.4, 23.1-23.4, 23.8, 24.4-24.7)
I.
Key Terms and Concepts
Conduction
Heat
Specific Heat Capacity
Kinetic Theory
Heat Engine
Radiant heat
Insulators
Land and sea breezes
Insolation angle
II.
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Convection
Temperature
Thermal Energy
Condensation
Heating System
Heat Flow
Conductors
Latent Heat
Radiation
Temperature scales
Absolute Zero
Evaporation
Cooling System
2nd law of thermodynamics
Entropy
Electromagnetic radiation
States of Matter
Keys
The total energy of the universe is constant. Energy can be transformed but
never destroyed.
Heat is the manifestation of the random motion and vibrations of atoms,
molecules, and ions.
The universe becomes less orderly and less organized over time (entropy).
III.
Essential Questions
1. How does matter respond to changes in temperature?
2. How does the transfer of thermal energy trend toward entropy?
3. How do heating and cooling systems transfer thermal energy?
IV.
Learning Targets
1. I can explain the difference between heat, temperature and thermal energy.
 Heat is the quantity of thermal energy transferred from a hotter to a
colder substance. Measured in joules.
 Temperature is the average kinetic energy of the particles that compose
matter, and is directly related to the speed of particle vibration
 Thermal energy is the sum of the kinetic and potential energy of the
particles that compose matter.
2. I can explain why a material will expand or contract when the temperature of
the material changes.
 As substances increase in temp., their particles speed up in vibration and
spread out, this causes the substance to expand
 As substances decrease in temperature, their particles slow down and get
closer, this causes the substance to contract.
 Rates of expansion and contraction vary due to the chemical composition
of the substance
3. I can explain how the kinetic theory helps us understand the transfer of
thermal energy.
 All matter is made of particles (molecules, etc.)
 These particles are moving randomly
 The faster they move, the higher the temperature
 When heat is transferred, it will cause the particles to speed up which
increases the temperature of the substance.
4. I can explain why heat flows and why it stops flowing.
 2nd law of thermodynamics
 Hotter substance lowers in temp, cooler substance raises in temp
 Heat flows from hot to colder temperature
 Heat flow continues until both substances reach the same temp. (Thermal
equilibrium)
5. I can explain the difference between a conductor and an insulator
 A conductor is a substance that transfers heat rapidly
 An insulator is a substance that slows down the transfer of heat
 Rates of conductivity are based upon the chemical composition of the
substance
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Metals are good conductors because they have free electrons in the outer
shell (easily moved)
Wood, glass, plastic, rubber and dead air are good insulators, and reduce
or slow down unwanted heat transfer
6. I can explain why and predict in which direction a bimetallic strip will bend.
 Bimetallic strip consists of two metals fused back to back that have
different rates of thermal expansion. Commonly brass and steel or copper
and steel.
 Brass (or copper) expands and contracts more rapidly than steel.
 When placed in a flame or in an area of higher temperature, the brass
expands more quickly, so it causes the steel to bend inward, forming an
arc with brass on the outside of the arc.
 When allowed to cool, the brass contracts more quickly, so it pulls inward,
forming an arc with steel on the outside of the arc.
7. I can explain the difference between a substance with a high specific heat
and a low specific heat capacity.
 Specific heat capacity is the amount of heat that is necessary to raise the
temperature of 1 kg of a substance by 1 degree C or 1 K.
 A substance with a low specific heat requires a relatively small amount of
heat to raise its temperature. Metals and land generally have low specific
heats.
 A substance with a high specific heat requires a large amount of heat to
raise its temperature. These substances are good at storing a large
amount of heat. Water and gases have high specific heats.
8. I can calculate the amount of thermal energy transferred to an object,
calculate the temperature change of the object and determine the
composition of the material using the specific heat equation.
 Q = cm Δ T [heat transferred = specific heat capacity x mass x change in
temp]
 Specific heats capacities are found in tables
 Q (joules), c (j/kg x K) m (kg) Δ T (K or C)
9. I can compare and contrast the three ways can the thermal energy of a
substance be transferred, which are conduction, convection and radiation.
 Conduction is the particle to particle transfer of heat between to
substance that are in direct contact
 Convection is the transfer of heat by the movement of heated matter due
to density differences (heated matter becomes less dense and rises,
cooler matter is more dense and sinks)
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Radiation is the transfer of heat by electromagnetic radiation (radiant or
light energy). The light energy is radiated and then is transferred to heat
when it is absorbed by the substance.
Conduction and convection require matter to transfer heat
Radiation can be transferred through matter or a vacuum (space)
10. I can explain radiant energy and its source.
Radiant energy is light energy produced by vibrating charged particles. The sun
is an obvious source of radiant energy, but all substances with temperatures
above 0 K (absolute zero) radiate “light” or electromagnetic waves.
11. I can explain why is evaporation a cooling process and condensation a
warming process
 Evaporation occurs when an influx of heat causes a liquid to change state
to a gas
 Evaporation is a cooling process because the heat required to change it to
a gas is drawn away from the surroundings, leaving the surroundings
cooler (particles speed up and take heat from the liquid when
evaporating)
 Condensation occurs when heat is released from a gas causing it to
change state to a liquid (particles slow down and give off heat when they
condense into a liquid)
 Condensation is a warming process because the heat released by the gas
is transferred into the surroundings, leaving the surroundings warmer
12. I can explain how thermal energy flow causes changes in phases of matter
and calculate latent heat using a heating curve.
 A heating curve shows what happens to the temperature of a substance
as it moves from one state of matter to another, solid to liquid to gas.
(heat is added)
 As long as a substance is in one state, heat added or released with cause
an increase or decrease in temperature.
 If the substance is in two states as it changes state, the heat added does
not change the temperature of the substance, but it does cause the
substance to change state (e.g., ice water, solid to liquid)
 A cooling curve shows what happens to temperature of a substance as is
moves from gas to liquid to solid. (heat is released)
13. I can compare and contrast the radiant heating and forced air heating
systems.
• Heating systems function to transfer heat to to a substance to raise the
temperature of the substance.
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Burn a fuel, heat a fluid, circulate a heated fluid, and transfer heat
(conduction, convection and/or radiation).
Radiant heating systems are radiation-dominated, with convection, and
circulate water as the heated substance.
Forced air heating systems are convection-dominated and circulate air as
the heated substance.
14. I can explain how air conditioners and refrigerators use evaporation and
condensation to cause cooling.
15. I can model how a heat engine transfers energy.
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A heat engine is any device that changes thermal energy into
mechanical energy so work can be done.
A steam engine burns fuel to heat water so it evaporates and increases
pressure, causing movement of a wheel or piston.
16. I can explain entropy and how natural systems tend to proceed.
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Entropy is the measure of disorder in a system.
All natural systems tend to proceed from a higher to lower state of
organization, or energy.
17. I can explain how land and sea breezes occur and its significance to specific
heat capacity.
The land raises temperature faster than water because it has a lower specific
heat. So given the same radiant energy from the sun, the land is warmer than
the water. Air above the land becomes heated, expands, gets less dense and
rises. The cooler, more dense air from the sea moves inland to replace the
hotter air that rises above the land. This produces a convection current. At
night, the high specific heat capacity of water allows it to absorb a large amount
of heat, which prevents water from rapidly losing the heat gained during the day
like the land. The air above the sea is now warmer and less dense than the air
over land, so the sea air rises and the land air moves off shore, producing
another convection current.
18. I can explain how an ocean and ocean currents can moderate climate.
 Warm ocean currents move from the equator towards the poles (the
earth’s oceanic mechanism of mixing warmer and cooler water which
prevents the earth from overheating at the equator). Since water has a
high specific heat, it does not transfer heat rapidly, and stores a large
amount of heat as well. In other words, water can keep a higher
temperature longer than the surrounding land masses.
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In the summer, water resists increasing in temperature as much as the
land, and provides cooling breezes for the land.
In the winter, water resists decreasing in temperature as much as the
land, and provides warming breezes for the land.
Water has a moderating effect on climate (not to hot and not to cold!)
19. I can describe the Earth’s external source of energy.
 The earth’s external source of energy is radiant energy from the Sun.
20.
I can explain insolation angle and its significance to climate.
 The insolation angle is the angle at which the sun strikes the Earth’s
surface.
 The higher the angle, the greater the intensity of the sun’s energy
received by the earth.
 The lower the angle, the lesser the intensity, but the greater the area
covered by the less intense sunlight.
What causes heat to flow?
Why do different substances have different capacities to store heat?
Substances with low specific heat don’t store much heat, most of the heat increases translational speed
(KE) of particles
Substances with high specific heat store a large quantity heat as PE first, and then increase in temperature
What happens to the thermal (internal) energy of a substance when it gives off heat?
What is the effect of water’s high specific heat capacity on climate?
The property of water to resist changes in temperature moderates the climate (not to hot, not to cold). A
large absorption of heat means that a large release of heat will occur when the substance decreases in
temperature.
The Gulf stream provides additional heat to Europe which was absorbed in the equatorial regions and is
slowly released as the stream flows north
Edmonton and Cork are cities at the same latitude with vastly different climates—continental climates are
extreme and maritime climates are moderated by the warmer gulf waters flowing in the Atlantic ocean
Ocean breezes keep the land cooler in the summer and warmer in the winter
Thermal expansion – particles that vibrate faster move farther apart
Bimetallic strips have two metals that expand at different rates and to different lengths. Brass or copper
expands and contracts to a longer length compared to steel. When hotter, the strip bends inward towards
steel; when colder the strip bends inward towards brass or copper
Pg. 424: 1,4,5,7,8,12,15,29,31,34-38
Why might a substance at the same temperature as different substance seem colder?
How can one end of a metal rod become warmer without causing it to be near a heat source?
Does cold transfer through materials?
How does a convection current develop?
Archimedes principle- less dense fluid buoyed up by denser surrounding fluid.
Heated fluid- increases in temperature, particles speed up causing expansion and a decrease in density
Good absorbers are also good emitters
Poor absorbers are poor emitters
Pg. 445 2,3,6-10, 12,14,22, 23, 33, 48
Change of phase or state of matter
Does evaporation cool or warm the liquid left behind. Explain
How does wetting the canvas covering a canteen keep the water inside the canteen cooler?
Does condensation cool or warm the area where the liquid forms?
Is energy as heat absorbed or released during boiling? Freezing? Melting? Condensing?
What is the heat of fusion?
What is the heat of vaporization?
What does a heating (or cooling) curve indicate about heat and temperature?
Pg 463 2,4,33
Describe the particles of a substance at absolute zero (0 K)
2nd law of thermodynamics – heat always flows from hot to cold
Heat engines change thermal energy into mechanical work (or mechanical energy)
Steam engine, internal combustion engines approximate heat engines
Systems tend to proceed towards a greater state of disorder
The measure of the disorder in a system is called entropy.
Physical systems trend from higher to lower states of energy
Week 8
Tuesday: Climate, Specific Heat, Moderating Effect of Water on Climate, 2 nd law of thermodynamics,
Heat Engines and Entropy (more review questions for HW)
Wednesday: Specific heat equation, heating curves and latent heat; class questions, lab work, thermal to
mechanical and mechanical to thermal; main points of lab, LTs are due. (more review questions)
Thursday: Review for test
Friday: Test, simple machines review (LTs)
Week 9
Monday: review for simple machines
Tues: Simple machines quiz
Wed: evaporation lab
Thursday: evaporation lab
Friday: Waves—new unit
Week 1
March 17-Fri—waves, sound and seismic
Week 2
March 24 (out)-waves
Week 3
April 7 waves
Week 4
April 14 light
Week 5
April 21 light
Week 6
April 28—light
Week 7
May 5 – elect mag
Week 8
May 12 –elect mag
Week 9
May 19 – nuclear power
Week 10
May 26 –nuclear power/review
Week 11
June 31 – review for exams