Chapter 5: Heat and Heat Transfer
Introduction
 Terminology
 Heat Energy vs. Thermal Energy

These two terms are essentially the same thing. They can be
used interchangeably.
Introduction
 What causes heat?
 Where does it come from and why?
 For over a century, scientists hotly debated the answers
to these questions as they worked to develop modern
heat theory.
 http://www.brainpop.com/science/energy/heat/
Introduction
 In a pre-match society, starting a fire was not the simple
task it is today.
 In many early societies, people who could start fires easily
were admired, often revered. If it was your job to keep the
fire going, letting it go out was considered a grievous
wrong.
5.1 The Nature of Heat
 Friction Theory
 when two surfaces are rubbed together, the parts that
touch resist movement
 This resistance is friction
 Count Rumford used observations about friction to
change the way scientists look at heat
5.1 The Nature of Heat
 Benjamin Thomson was an engineer and scientist who
lived in the Thirteen Colonies at the time of the
American Revolution.
 Because he stayed loyal to Britain, many Americans
considered him a traitor.
 British loyalists, however, considered him a hero.
 Thomson was given the title of Count Rumford to
reward him for his loyalty to Britain.
5.1 The Nature of Heat
 Rumford was an engineer/scientist who was hired to
manufacture cannons in Munich, Germany.
 During this project, one worker carelessly touched a
rod being used to bore a hold through a piece of metal.
His hand was seriously burned.
 In the late 1700s, Count Rumford observed that heat
was created when metal cut metal.
 This heat results from friction!
5.1 The Nature of Heat
 Have you ever watched popcorn popping in an air
popper?
 The random, dancing motion of the kernels is easy to
observe.
 But what causes this motion?
5.1 The Nature of Heat
 A similar type of motion is occurring in a glass of
water.
5.1 The Nature of Heat
 Robert Brown – the first to realize this similarity
 During the 1800s he was using a microscope to observe
pollen grains in a drop of water.
 He noticed that although the microscope was quite still,
the pollen grains bounced around.
 When he increased the temperature of the water, the
motion increased.
 This motion has become known as Brownian Motion
http://www.youtube.com/watch?v=hy-clLi8gHg
5.1 The Nature of Heat
 Making the observation was easy.
 But how can we explain it?
5.1 The Nature of Heat
 At first, Brown thought that the pollen grains were
alive.
 Later he reasoned that water must be composed of tiny
unseen particles. These particles are in constant,
vibrating motion.
 The motion of the pollen grains must be caused by
collisions between the pollen grains and the other
unseen particles. (Brown was unsure of what the
particles were)
 Later, his evidence helped develop the kinetic
molecular theory.
Kinetic Molecular Theory
 http://www.youtube.com/watch?v=_rsqBNhFG1Y
5.1 The Nature of Heat
 The concept of heat is commonplace; what causes heat
is fairly abstract.
 Technically, heat is defined as the transfer of
energy from one substance to another and is
identified by a difference in temperature.
 An object does not possess heat. Rather, an object
possesses thermal energy and can lose that energy in
the process of heat loss.
5.1 The Nature of Heat
 It is a common misconception to think of heat as a
thing rather than a process.
 This probably stems from the original caloric
definition of heat.
 Scientists thought that something measurable left an
object when it got colder.
 Recall that Rumford was able to gain a scientific
understanding of heat through observations of
friction.
5.1 The Nature of Heat
 Before Rumford, scientists thought heat was a fluid
they called caloric.
 Rumford did not replace the caloric theory. Rather,
he demonstrated an inconsistency in the theory.
 Two later British scientists — Sir Humphry Davy and
James Prescott Joule took Rumford’s ideas to the next
step.
5.1 The Nature of Heat
 Davy, an English chemist,
designed demonstrations to
disprove the caloric
theory.
 He rubbed ice and other
solids with low melting
points together to show that
they would melt with heat
from friction.
5.1 The Nature of Heat
 Joule determined the mechanical
equivalent of heat by measuring the
change in temperature produced by
friction.
 Working in imperial measure, he
found that, on average, a weight of 772
pounds falling through a distance of
one foot would raise the temperature
of one pound of water by 1°F.
 In addition, Joule’s investigations
showed that heat is produced by
motion, contradicting the caloric
theory.
5.1 The Nature of Heat
 We can relate this to the calorie, which is related to
food energy.
 The calorie is a unit of energy. One calorie is the
amount of energy needed to raise 1 gram of water by
1°C.
 Other units of energy are the joule — named after
James Prescott Joule and the British Thermal Unit
(BTU).
 The BTU is used in Canada to rate thermal output of
stoves, ovens, and barbecues.
5.1 The Nature of Heat
 Mysterious Motion Lab
 P. 84
 Materials: 2 glasses, food colouring, hot/cold water
5.1 The Nature of Heat
5.1 The Nature of Heat
 Practice!
 Check Your Understanding p. 85 #1-3
5.2 Heat and Temperature
 The modern theory of heat began with Robert Brown
 He was the first to suggest that the energy that came
with heat – thermal energy – was related to the
motion of unseen particles of a substance.
 But, what are these unseen particles? What causes the
motion?
5.2 Heat and Temperature
 Recall the Particle Theory of Matter:
 All matter is composed of tiny, unseen particles
 These unseen particles are in constant, random
motion.
5.2 Heat and Temperature
 Kinetic – means movement
 Kinetic Art – art that moves (i.e. Mobiles)
 Kinetic Energy – a form of energy associated with
motion
 It is a measure of the amount of motion particles have.
 We can use kinetic energy to explain the difference
between heat and temperature
5.2 Heat and Temperature
 A molecule can have three different forms of
movement:
 Vibrational — molecules “vibrate” back and forth
 Rotational — molecules spin and rotate
 Translational — molecules bump and move around
5.2 Heat and Temperature
 The motion of particles can be compared to bumper
cars!
5.2 Heat and Temperature
 Like bumper cars, atoms and molecules collide with
each other at different speeds.
 All particles have different kinetic energies.
5.2 Heat and Temperature
 So what is the difference between heat and
temperature?
 Temperature – the average of ALL kinetic energies
of all particles in an object
 Heat – the sum of all kinetic energies of all
particles in an object
5.2 Heat and Temperature
 Example:
25 mL
Temperature: 30°C
Less kinetic energy
100 mL
Temperature: 30°C
More kinetic energy
5.2 Heat and Temperature
 Because temperature is a measure of how fast
molecules are, and because molecules slow as they get
colder, the coldest possible temperature is finite!
Particles truly stop moving at absolute zero. Absolute
zero is -273.15°C
 The lowest artificial temperature achieved to date is
0.003°K. The highest is estimated at 100 000 000°K and
was from a nuclear blast.
5.2 Heat and Temperature
 There are more temperature scales than Celsius and
Fahrenheit. The Kelvin scale (K) starts at absolute
zero and rises in degrees equal in magnitude to
Celsius degrees.
 Other scales include the Rankine scale and the
International Temperature Scale.
5.2 Heat and Temperature
 Eureka Videos (links on powerschool)
 Practice!
 Check Your Understanding p. 87 #1-4
5.3 Transfer of Heat
 There have been many predictions about when Earth
will end.
 Fear of Y2K computer problems brought excitement to
New Year’s Eve 2000.
 As we study heat transfer, we will learn about another
proposed end to the universe 
5.3 Transfer of Heat
 Forms of Heat Transfer
 Heat flows from hot to cold.
 The flow continues until both objects are at the same
temperature.
 But what is really happening? How does thermal energy
transfer from one object to another?
5.3 Transfer of Heat
 Conduction
 Molecules placed on a hot burner will vibrate quickly.
 They have more kinetic energy than the molecules in a
cooler location (a cool pot).
 Contact between the pot and the burner causes the
molecules of the hot burner to collide with the slower
molecules of the cool pot.
 These collisions result in a transfer of kinetic energy.
5.3 Transfer of Heat
 The molecules of the cooler pot start to vibrate faster,
gaining kinetic energy.
 The molecules of the hot burner vibrate slower,
losing kinetic energy.
 This transfer of heat by contact is called conduction.
5.3 Transfer of Heat
 Thermal conductivity and electrical conductivity are
related.
 Substances that conduct electricity will also tend to be
good thermal conductors.
 Metal is a good example of this. Conversely, glass and
wood are poor thermal and poor electrical conductors.
5.3 Transfer of Heat
 Convection
 If you hold your hand above a hot burner of a stove, you
will feel a warm current of air.
 Why?


Heat is transferred, by conduction, from the hot burner to
the air molecules touching the burner.
These air molecules gain kinetic energy, vibrate faster, and
get farther apart.
5.3 Transfer of Heat
 The warmer molecules are farther apart than the cool
air molecules, so the warm air is less dense than the
cool air around it.
 This causes the warm air to rise, creating the warm
current that we feel.
 Cool, denser air rushes to take the place of the warm
air.
5.3 Transfer of Heat
 Because of continuous air flow, all the air in the room
will become warmer.
 This transfer of heat by movement is called
convection.
Convection is why firefighters crawl
on the floor…..
5.3 Transfer of Heat
 Radiation
 Picturing a hand that is close to the side of a burner, but
not above the burner can help us explain radiation.
 The front of the hand is not being heated by
conduction or convection.
 There is no contact with the burner and convection
currents of warm air would rise away from the hand.
Radiation Examples
Heat is
transmitted
through an empty
space.
5.3 Transfer of Heat
 The front the hand is being heated by radiation.
 Radiation is produced by vibrating electrons, which
are tiny particles present in all atoms.
 This vibration makes a wave called an
electromagnetic wave or infrared radiation wave.
 These waves are similar to the waves your hand can
create when it vibrates in calm water.
 Waves or ripples run away from your moving hand.
5.3 Transfer of Heat
 Infrared radiation waves travel from the burner.
 They strike the hand and transfer heat energy to the
molecules in the hand.
 This causes molecules in the hand to vibrate faster.
5.3 Transfer of Heat
 On a sunny day, most of the heat that you feel is the
result of infrared radiation from the Sun.
 Infrared radiation is one form of electromagnetic
radiation. Other forms include ultraviolet radiation,
radio waves, visible light waves, and X rays.
 Electromagnetic radiation travels in waves. Each type
of electromagnetic radiation has a specific
wavelength and moves through the vacuum of space.
5.3 Transfer of Heat
5.3 Transfer of Heat
 Did You Know?
 Hot objects warm cool ones until their temperatures are
the same.
 Some people believe this will happen to the universe.
 According to the theory, the temperature of the entire
universe will eventually be the same.
 When this happens, heat will no longer transfer.
 Without a source of energy, life will be impossible!
 This prediction is called the “Heat Death of the
Universe.”
5.3 Transfer of Heat
 Practice!
 Check Your Understanding p. 91 #1-4
5.4 Heat Transfer in Nature
 Convection causes many weather phenomena, such




as winds.
Many cottages are on the shores of lakes, where
convection currents keep the cottages cool in the
daytime and warmer at night.
In the evening, the air over the water cools more
slowly than the air over the land.
Warm air from over the water rises and moves toward
the land, keeping it warm.
During the day, cool air from the lake moves towards
the warm land.
Convection!!
5.4 Heat Transfer in Nature
 Sea and Land Breezes
 Recall: warm air rises, and cool air sinks
 The circular movement that results is called
convection.
 All winds start with convection currents.
5.4 Heat Transfer in Nature
 Land and sea breezes are convection currents of air
that occur near a shoreline.
 They are both created by differences in temperature
near the surface of the Earth.
5.4 Heat Transfer in Nature
 On a sunny day, radiant heat from the Sun strikes
Earth’s surface.
 Heat is absorbed by land and water. But land and
water heat at different rates.
 Land heats quickly, but also cools quickly.
 Water heats slowly and takes longer to cool.
5.4 Heat Transfer in Nature
Day Time – Sea Breeze
Night Time – Land Breeze
5.4 Heat Transfer in Nature
 How Oceans Help to Moderate Climates
 Oceans are capable of storing large amounts of thermal
energy.
 This prevents the area around them from having
extreme temperature changes.
 Oceans moderate the climate of land areas near them.
 This means they prevent the area from becoming too
hot or too cold.
 But how???
5.4 Heat Transfer in Nature
 In cool weather, an ocean can release great amounts
of heat without cooling much itself.
 Even during very hot or very cold days, and as seasons
change, the temperature of oceans remains constant.
 As the sun warms the air above the ocean, heat flows
from the air into the water, cooling the air.
 When the temperature of the air above the ocean
cools, heat flows from ocean to air and warms the air.
5.4 Heat Transfer in Nature
 We could say that oceans prevent land near them from
getting very warm or very cold.
 Because of this, coastal cities (like Vancouver) have
moderate climates.
Circulation of Ocean Surface Water
Warm currents are noted in the color red and cold currents are noted in the color blue.
Compare the climate in Canada to
the climate in England…..
5.4 Heat Transfer in Nature
Chinooks – Warm West Winds
If hot air rises, why is it cold in the
mountains?
5.4 Heat Transfer in Nature
 Ocean Currents and Climate
https://www.youtube.com/watch?v=HgoANl_97kM
 Bill Nye - Currents
https://www.youtube.com/watch?v=KuSB6HNRT2s
 Practice!
 Check Your Understanding p. 97 #1-3
5.5 Heat Transfer and Technologies
 Many household technologies either transfer or
prevent the transfer of heat through conduction,
convection or radiation.
 That is why metal cooking pots have hard plastic or
wooden handles.
 What other techniques are used to handle hot
food?
5.5 Heat Transfer and Technologies
 Stoves
 Most cooks want to control how food is heated.
 Consider the following: heating soup on a stove top.
 The pot is heated by conduction through contact with
the burner.
 The soup at the bottom of the pot heats up first
through conduction.
5.5 Heat Transfer and Technologies
 Heated soup rises to the top, because it is less dense.
 Colder soup near the top of the pot flows to the bottom
because it is more dense.
 This causes a circular motion (aka convection
currents) and allows the entire pot of soup to heat to a
uniform temperature.
5.5 Heat Transfer and Technologies
 Ovens
 When an oven is turned on, convection currents
move heat inside the oven.
 Air at the bottom of the oven is heated by burning gas
or an electric element.
 The heated air becomes less dense and rises to the
top of the oven.
 The cooler air sinks to the bottom.
5.5 Heat Transfer and Technologies
 The hot air heats the oven walls.
 These walls then radiate heat in all directions.
 Food in an oven then becomes cooked by both
convection and radiation.
 There is also conduction if a baking pan is used.
5.5 Heat Transfer and Technologies
 Did you know?
 Light-coloured surfaces
reflect more heat than dark
surfaces.
 This is why people in hot
countries often wear lightcoloured clothing.
5.5 Heat Transfer and Technologies
 Getting Rid of the Heat
 Combustion of fuel inside an engine produces a large
quantity of thermal energy.
 If this energy were not removed, the engine would
overheat and be damaged.
 How is it protected?
5.5 Heat Transfer and Technologies
 The engine’s cooling system contains a liquid coolant
(most likely antifreeze).
 The coolant is pumped through the engine block to
the radiator. A radiator is a honeycomb made of a
metal alloy. The metal alloy is a good conductor.
Heat from the coolant is conducted through this alloy
to air.
5.5 Heat Transfer and Technologies
 Either a fan or the motion of the vehicle forces this
air through the radiator. Heat is transferred to the air
that rushes through the radiator.
 These three techniques use conduction to protect
engines from heat damage.
5.5 Heat Transfer and Technologies
 Keeping it Cool
 When you put a little water on the back of your hand,
your hand becomes cool.
 That is because thermal energy transfers from your
hand to the water through conduction.
 Water absorbs heat from your hand and evaporates.
 Evaporation removes thermal energy as the water
molecules leave the water droplets and move into the
air.
 Your hand feels cooler.
5.5 Heat Transfer and Technologies
 This form of cooling is usually called cooling by
evaporation.
 The evaporation caused the cooling, but the cooling
action started with conduction of heat away from
your hand.
5.5 Heat Transfer and Technologies
 Heat Transfer in a Refrigerator
 A. A fluid called a coolant circulates through the pipes.
 B. Heat from the food transfers to the cooler air
surrounding it. Thermal energy then transfers from the air
to the coolant.
 C. The coolant evaporates as it gets warmer. It is pumped to
the compressor.
 D. When it reaches the compressor, pressure is applied to
change it back into a liquid.
 E. The liquid coolant is pumped to these coils. Thermal
energy is released into the room. The cycle starts again.
5.5 Heat Transfer and Technologies
 Air conditioners work in a similar manner. In this case,
the back of the unit is outside the room or house. To
keep the inside of the room cool, heat is dispersed to
the outside air.
 Although useful, coolant technology has an
environmental cost. For the past 50 years, the liquid
coolant used in refrigerators and air conditioners has
been liquid chlorofluorocarbons, or CFCs. CFCs are
responsible for atmospheric ozone depletion. As of
January 2000, worldwide production of the most
dangerous CFCs was to be replaced by alternative
liquid coolants. Research is underway to produce
environmentally safer but effective coolants.
CFC Cycle
5.5 Heat Transfer and Technologies
 Practice!
 Check Your Understanding p. 101 #1-4
REVIEW
 Chapter 5 Review p. 102 #1 – 12
 Hand-in Assignment #5
Review
 Complete review questions on pg. 126
 Hand-in Assignment #6