Chapter Introduction
Lesson 1 Thermal Energy,
Temperature,
and Heat
Lesson 2 Thermal Energy
Transfers
Lesson 3 Using Thermal
Energy
Chapter Wrap-Up
Do you agree or disagree?
1. Temperature is the same as thermal
energy.
2.
Heat is the movement of thermal energy
from a hotter object to a cooler object.
3. It takes a large amount of energy to
significantly change the temperature of an
object with a low specific heat.
4. The thermal energy of an object can never
be increased or decreased.
Thermal Energy, Temperature,
and Heat
• How are temperature and kinetic
energy related?
• How do heat and thermal energy
differ?
Thermal Energy, Temperature,
and Heat
- in your own words come up
with a definition for each of the words below
• thermal energy
• temperature
• heat
Kinetic and Potential Energy
• Potential energy is stored energy due
to the interaction between two objects.
• The potential energy plus the kinetic
energy of an object is the mechanical
energy of the object.
What is thermal energy?
• Every solid, liquid, and gas is made
up of trillions of tiny particles that are
constantly moving.
• Because particles are in motion, they
have kinetic energy.
• The faster particles move, the more
kinetic energy they have.
What is thermal energy? (cont.)
• The greater the average distance
between particles, the greater the
potential energy of the particles.
• Thermal energy is the sum of the kinetic
energy and the potential energy of the
particles that make up a material.
The potential energy of the soccer ball depends
on the distance between the ball and Earth.
The potential energy of the particles of matter
depends on their distance from one another.
What is thermal energy? (cont.)
• Mechanical energy describes the energy
of one object.
• Thermal energy describes the energy of
the particles that make up a solid, liquid,
or gas.
What is temperature?
• Scientists define temperature in terms
of kinetic energy.
• Temperature represents the average
kinetic energy of the particles that make
up a material.
What is temperature? (cont.)
• The greater the average kinetic energy
of particles, the greater the temperature.
• The particles in warmer air move at a
greater average speed than the particles
in colder air.
What is temperature? (cont.)
• Temperature and thermal energy are
related, but they are not the same.
• The particles that make up liquid and
solid water have different potential
energies and, therefore, different thermal
energies.
What is temperature? (cont.)
• Thermometers are used to measure
temperature.
• Common
temperature
scales are
Celsius (°C),
Kelvin (K),
and Fahrenheit (°F).
What is heat?
• The movement of thermal energy from
a warmer object to a cooler object is
called heat.
• All objects have thermal energy;
however, you heat something when
thermal energy transfers from one
object to another.
• The rate at which heating occurs
depends on the difference in
temperatures between the objects.
• The greater the
distance between
two particles or two
objects, the greater
the potential energy.
• Heat is the movement
of thermal energy from
a warmer object to a cooler object.
• When thermal energy
moves between a
material and its
environment, the
material’s temperature
changes.
Because particles are in motion,
what type of energy do they have?
A. thermal energy
B. potential energy
C. mechanical energy
D. kinetic energy
Particles that make up liquid and
solid water have different potential
energies, and therefore also have
which of the following?
A. different thermal energies
B. different temperatures
C. different kinetic energies
D. the same thermal energy
Which term refers to the average
kinetic energy of the particles that
make up a material?
A. heat
B. temperature
C. potential energy
D. thermal energy
Do you agree or disagree?
1. Temperature is the same as thermal
energy.
2. Heat is the movement of thermal
energy from a hotter object to a cooler
object.
Thermal Energy Transfers
• What is the effect of having a small
specific heat?
• What happens to a material when it is
heated?
• In what ways can thermal energy be
transferred?
Thermal Energy Transfers
• radiation
• conduction
• thermal conductor
• thermal insulator
• specific heat
• thermal
expansion
• thermal
contraction
• convection
• convection
current
How is thermal energy transferred?
• Thermal energy is transferred in three
ways.
• by radiation
• by conduction
• by convection
Radiation
• The transfer of thermal energy from one
material to another by electromagnetic
waves is called radiation.
• Radiation is the only way thermal energy
can travel from the Sun to Earth,
because space is a vacuum.
• Radiation also transfers thermal energy
through solids, liquids, and gases.
Conduction
• When particles with different kinetic
energies collide, the particles with higher
kinetic energy transfer energy to
particles with lower kinetic energy.
• The transfer of thermal energy between
materials by the collisions of particles is
called conduction.
• Conduction continues until the thermal
energy of all particles in contact is equal.
Conduction
(cont.)
• The hot air transfers
thermal energy to,
or heats, the cool
lemonade by
conduction.
• Eventually the kinetic
thermal energy and
temperature of the air
and the lemonade will
be equal.
Conduction
(cont.)
• A thermal conductor is a material
through which thermal energy flows
easily.
• A thermal insulator is a material
through which thermal energy does not
flow easily.
Conduction
(cont.)
• The amount of thermal energy required
to increase the temperature of 1 kg of a
material by 1°C is called specific heat.
• Water’s high specific heat helps
prevent your body from overheating.
• Changing the temperature of a material
with a low specific heat is easier than to
change the temperature of a material
with a high specific heat.
In a hot car, the temperature of thermal
conductors, such as the safety-belt buckles,
increases more
quickly than the
temperature of
thermal insulators,
such as the
seat material.
Units of heat and
thermal energy
• The metric unit for
measuring heat is
the joule.
• This is the same
joule used to
measure all forms
of energy, not just
heat.
Heat and thermal energy
• Thermal energy is often measured in calories.
• One calorie is the amount of energy it takes to
raise the temperature of one milliliter of water by
one degree Celsius.
Specific Heat
• The specific heat is
a property of a
substance that tells
us how much heat
is needed to raise
the temperature of
one kilogram of a
material by one
degree Celsius.
Knowing the specific heat of a material tells you how
quickly the temperature will change as it gains or loses
energy.
Why is specific heat different for
different materials?
• Temperature measures the average kinetic energy
per particle.
• Energy that is divided between fewer particles
means more energy per particle, and therefore
more temperature change.
• In general, materials made up of heavy atoms or
molecules have low specific heat compared with
materials made up of lighter ones.
Conduction
(cont.)
What does it mean if a material
has a low specific heat?
The heat equation
Solving Problems
•
How much heat is needed to raise the
temperature of a 250-liter hot tub from
20°C to 40°C?
Solving Problems
1. Looking for:
–
…amount of heat in joules
2. Given:
–
V = 250 L, 1 L of water = 1 kg
–
Temp changes from 20°C to 40°C
–
Table specific heat water = 4, 184 J/kg°C
3. Relationships:
–
E = mCp(T2 – T1)
4. Solution:
 E = (250L × 1kg/L) × 4,184 J/kg°C (40°C - 20°C) =
20,920,000 J
Sig. fig./Sci. not. 20,920,000 J = 2.1 x 107 J
Thermal Expansion and Contraction
• Thermal contraction is a decrease in a
material’s volume when its temperature
decreases.
• Thermal expansion is an increase in a
material’s volume when its temperature
increases.
• Thermal expansion and contraction are
most noticeable in gases, less noticeable
in liquids, and the least noticeable in
solids.
Thermal Expansion and Contraction
(cont.)
What happens to the volume of
a gas when it is heated?
Convection
• Convection is the transfer of thermal
energy by the movement of particles
from one part of a material to another.
• Convection only occurs in fluids.
convection
from Greek convectionem,
means “the act of carrying”
This cycle of cooler water sinking and
forcing warmer water upward is an example
of convection.
Convection (cont.)
What are the three processes that
transfer thermal energy?
Convection (cont.)
• The movement of fluids in a cycle
because of convection is a convection
current.
• Convection currents circulate the water
in Earth’s oceans and other bodies of
water.
Convection Currents in Earth’s Atmosphere
• When a material has a low specific
heat, transferring a small amount of
energy to the material increases its
temperature
significantly.
• Thermal energy can be transferred
through radiation, conduction, or
convection.
• When a material is heated, the
thermal energy of the material
increases and the material expands.
Which term refers to a material
through which thermal energy
flows easily?
A. convection current
B. specific heat
C. thermal conductor
D. thermal insulator
Which describes an increase in
a material’s volume when its
temperature increases?
A. conduction
B. thermal expansion
C. thermal conductor
D. thermal contraction
What term describes the transfer
of thermal energy by the
movement of particles from one
part of a material to another?
A. convection
B. conduction
C. thermal contraction
D. thermal expansion
Do you agree or disagree?
3. It takes a large amount of energy to
significantly change the temperature of
an object with a low specific heat.
4. The thermal energy of an object can
never be increased or decreased.
Using Thermal Energy
• How does a thermostat work?
• How does a refrigerator keep food
cold?
• What are the energy transformations
in a car engine?
Using Thermal Energy
• heating appliance
• thermostat
• refrigerator
• heat engine
Do you agree or disagree?
5. Car engines create energy.
6. Refrigerators cool food by moving
thermal energy from inside the
refrigerator to the outside.
Thermal Energy Transformations
• Thermostats transform thermal energy
into mechanical energy that switch
heaters on and off.
• Even though many devices transform
energy from one form to another or
transfer energy from one place to
another, the total amount of energy does
not change.
Heating Appliances
• A device that converts electric energy
into thermal energy is a heating
appliance.
• Curling irons, coffeemakers, and clothes
irons are some examples of heating
appliances.
Thermostats
A thermostat is a device that regulates
the temperature of a system.
thermostat
from Greek therme, meaning “heat”;
and statos, meaning “a standing”
Thermostats (cont.)
• Most thermostats contain a bimetallic coil
made of two types of metal joined
together and bent into a coil.
• The metal on the inside of the coil
expands and contracts more than the
metal on the outside of the coil.
• When a room warms or cools, the
thermal energy causes the bimetallic coil
to uncurl slightly or tighten, which turns
the furnace off or on.
Refrigerators
• A device that uses electric energy to
transfer thermal energy from a cooler
location to a warmer location is called a
refrigerator.
• In a refrigerator, a coolant is pumped
through pipes on the inside and the
outside of the refrigerator.
Coolant in a
refrigerator
moves thermal
energy from
inside to outside
the refrigerator.
The coolant,
which begins as
a liquid, passes
through an
expansion valve
and cools.
As the cold gas
flows through
pipes inside the
refrigerator, it
absorbs thermal
energy from
the refrigerator
compartment
and vaporizes.
Heat Engines
• A heat engine is a machine that
converts thermal energy into mechanical
energy.
• When a heat engine converts thermal
energy into mechanical energy, the
mechanical energy moves the vehicle.
• Most cars, buses, boats, trucks, and
lawn mowers use a type of heat engine
called an internal combustion engine.
Internal Combustion Engine
Internal Combustion Engine
Heat Engines (cont.)
What is one form of energy that
is output from a heat engine?
• A bimetallic coil inside a thermostat
controls a switch that turns a heating
or cooling device on or off.
• A refrigerator keeps
food cold by moving
thermal energy from
the inside of the
refrigerator out to the
refrigerator’s
surroundings.
• In a car engine,
chemical energy in
fuel is transformed into
thermal energy. Some
of this thermal energy
is then transformed
into mechanical
energy.
Curling irons, coffeemakers, and
clothes irons are some examples
of what?
A. thermostats
B. refrigerators
C. heat engines
D. heating appliances
Which is pumped through pipes
on the inside and the outside of
a refrigerator?
A. water
B. ice
C. coolant
D. bimetallic coil
Which term refers to a device
that regulates the temperature
of a system?
A. heat engine
B. heating appliance
C. refrigerator
D. thermostat
Do you agree or disagree?
5. Car engines create energy.
6. Refrigerators cool food by moving
thermal energy from inside the
refrigerator to the outside.
Key Concept Summary
Interactive Concept Map
Chapter Review
Standardized Test Practice
Thermal energy can be
transferred by
conduction, radiation,
and convection.
Thermal energy also
can be transformed
into other forms of
energy and used in
devices such as
thermostats,
refrigerators, and
automobile engines.
Lesson 1: Thermal Energy, Temperature,
and Heat
• The temperature of a material is the average kinetic
energy of the particles that make up the material.
• Heat is the movement of thermal energy from a
material or area with a higher temperature to a
material or area with a lower temperature.
• When a material is heated, the material’s
temperature changes.
Lesson 2: Thermal Energy Transfers
• When a material has a low specific heat, transferring
a small amount of energy to the material increases
its temperature significantly.
• When a material is heated, the thermal
energy of the material increases and
the material expands.
• Thermal energy can be transferred
by conduction, radiation, or convection.
Lesson 3: Using Thermal Energy
• The two different metals in a bimetallic coil inside a
thermostat expand and contract at different rates.
The bimetallic coil curs and uncurls, depending on
the thermal energy of the air, pushing a switch that
turns a heating or cooling device on or off.
• A refrigerator keeps food cold by moving
thermal energy from inside the refrigerator
out to the refrigerator’s surroundings.
• In a car engine, chemical energy in fuel
is transformed into thermal energy.
Some of this thermal energy is then
transformed into mechanical energy.
Which describes the sum of the
kinetic energy and the potential
energy of the particles that make
up a material?
A. heat
B. temperature
C. thermal energy
D. mechanical energy
The transfer of thermal energy
from one material to another by
electromagnetic waves is called
what?
A. conduction
B. radiation
C. specific heat
D. thermal expansion
Which refers to a decrease in
a material’s volume when its
temperature decreases?
A. conduction
B. radiation
C. thermal contraction
D. thermal expansion
Which describes the amount
of thermal energy required to
increase the temperature of 1 kg
of a material by 1°C?
A. thermal expansion
B. specific heat
C. convection
D. conduction
What term refers to the part of
a thermostat that expands and
contracts to turn a furnace on and
off?
A. coolant
B. piston
C. bimetallic coil
D. heat engine
What term refers to the movement
of thermal energy from a warmer
object to a cooler object?
A. temperature
B. heat
C. potential energy
D. kinetic energy
Which term refers to a material
through which thermal energy
does not flow easily?
A. convection current
B. thermal contraction
C. thermal conductor
D. thermal insulator
Which is the movement of fluids
in a cycle because of convection?
A. convection current
B. thermal contraction
C. thermal expansion
D. thermal conductor
Which term describes the transfer
of thermal energy between
materials by the collisions
of particles?
A. convection
B. conduction
C. thermal expansion
D. thermal contraction
Which describes a machine that
converts thermal energy into
mechanical energy?
A. piston
B. thermostat
C. heat engine
D. heating appliance