Download Thermal energy - geraldinescience

Chapter Introduction
Lesson 1 Thermal Energy,
Temperature,
and Heat
Lesson 2 Thermal Energy
Transfers
Lesson 3 Using Thermal
Energy
Chapter Wrap-Up
How can thermal energy
be used?
What do you think?
Before you begin, decide if you agree or
disagree with each of these statements.
As you view this presentation, see if you
change your mind about any of the
statements.
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.
Do you agree or disagree?
4. The thermal energy of an object can
never be increased or decreased.
5. Car engines create energy.
6. Refrigerators cool food by moving
thermal energy from inside the
refrigerator to the outside.
Thermal Energy, Temperature,
and Heat
• How are temperature and kinetic
energy related?
• How do heat and thermal energy
differ?
Thermal Energy, Temperature,
and Heat
• 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 *.
• 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 *.
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 *
What is temperature? (cont.)
temperature
from Latin temperatura, means
“moderating, tempering”
What is temperature? (cont.)
• The greater the average kinetic energy
of particles, the *.
• The particles in warmer air move at a
greater average speed than the particles
in colder air.
What is temperature? (cont.)
How are temperature and
kinetic energy related?
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 *.
What is temperature? (cont.)
• Thermometers are used to measure
temperature.
• Common
temperature
scales are
Celsius (°C),
Kelvin (K),
and Fahrenheit (°F).
What is heat?
• * 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.
What is heat? (cont.)
How do heat and thermal
energy differ?
• 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.
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.
•*
•*
•*
Radiation
• * 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.
Radiation (cont.)
vacuum
Science Use a space that contains
little or no matter
Common Use a device for cleaning
carpets and rugs that uses suction
Conduction
• When particles with different kinetic
energies collide, the particles with higher
kinetic energy transfer energy to
particles with lower kinetic energy.
• * 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 *
• A thermal insulator is a *
Conduction
(cont.)
• * 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.
Conduction
(cont.)
What does it mean if a material
has a low specific heat?
Thermal Expansion and Contraction
• Thermal contraction is a *
• Thermal expansion is an *
• 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 *.
• 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.)
• * 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.
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
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
• * is a heating appliance.
• Curling irons, coffeemakers, and clothes
irons are some examples of heating
appliances.
Thermostats
A thermostat is a *.
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.
Thermostats (cont.)
How does the bimetallic coil
in a thermostat respond to
heating and cooling?
Refrigerators
• * 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.
Refrigerators (cont.)
How does a refrigerator keep
food cold?
Heat Engines
• A heat engine is a *
• 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.
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.