Transcript Chapter 7 Powerpoint - Ms. Griffin

Chapter Introduction
Lesson 1 Forms of
Energy
Lesson 2 Energy
Transformations
Lesson 3 Thermal Energy
on the Move
Chapter Wrap-Up
What is energy, and
what are energy
transformations?
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. A fast-moving baseball has more kinetic
energy than a slow-moving baseball.
2. A large truck and a small car moving at
the same speed have the same kinetic
energy.
Do you agree or disagree?
3. Energy can change from one form to
another.
4. Energy is destroyed when you apply
the brakes on a moving bicycle or a
moving car.
Do you agree or disagree?
5. Warm water sinks below cool water
when they are in the same container.
6. Wearing a coat slows the loss of
thermal energy from your body.
Forms of Energy
• What is energy?
• What are potential and kinetic energy?
• How is energy related to work?
• What are different forms of energy?
Forms of Energy
•
•
•
•
•
energy
kinetic energy
potential energy
work
mechanical
energy
•
•
•
•
•
sound energy
thermal energy
electric energy
radiant energy
nuclear energy
What is energy?
• Energy is the ability to cause change.
• Energy can cause changes in the
motions of objects.
energy
from Greek energeia, means
“activity”
What is energy? (cont.)
What is energy?
Kinetic Energy—Energy of Motion
• Kinetic energy is energy due to motion.
• All moving objects have kinetic energy.
• The faster an object moves, the more
kinetic energy it has.
• If two objects move at the same speed,
the object with more mass has more
kinetic energy.
The kinetic energy (KE) of an object
depends on its speed and its mass. The
vertical bars show the kinetic energy of
each vehicle.
Kinetic Energy—Energy of Motion
(cont.)
What is kinetic energy?
Potential Energy—Stored Energy
• Potential energy is stored energy due
to the interactions between objects or
particles.
• The gravitational potential energy stored
between an object and Earth depends on
the object’s weight and height.
• Elastic potential energy is energy stored
in objects that are compressed or
stretched.
Chemical potential energy is energy stored
in the chemical bonds between atoms.
Potential Energy—Stored Energy (cont.)
In what way are all forms of
potential energy the same?
Energy and Work
• Work is the transfer of energy that
occurs when a force is applied over a
distance.
• Work depends on both force and
distance.
• You only do work on an object if that
object moves.
The girl does work on the box as she lifts it.
The work she does transfers energy to the
box. The colored bars show the work that
the girl does (W) and the box’s potential
energy (PE).
Energy and Work (cont.)
How is energy related to work?
All energy can be measured in joules (J).
Other Forms of Energy
Describe three forms of energy.
• Energy is the
ability to cause
change.
• The gravitational
potential energy between an object
and Earth increases when you lift the
object.
• You do work on an object when you
apply a force to that object over a
distance.
Which type of energy is described
as the total energy of an object or
group of objects due to largescale motions and interactions?
A. electric energy
B. mechanical energy
C. radiant energy
D. thermal energy
What is the transfer of energy that
occurs when a force is applied
over a distance?
A. work
B. electric energy
C. kinetic energy
D. potential energy
Which term refers to energy due
to motion?
A. kinetic energy
B. potential energy
C. sound energy
D. stored energy
Do you agree or disagree?
1. A fast-moving baseball has more
kinetic energy than a slow-moving
baseball.
2. A large truck and a small car moving at
the same speed have the same kinetic
energy.
Energy Transformations
• What is the law of conservation of
energy?
• How does friction affect energy
transformations?
• How are different types of energy
used?
Energy Transformations
• law of conservation of energy
• friction
Changes Between Forms of Energy
The changes from one type of energy to
another type of energy are called energy
transformations.
A microwave oven changes electric energy
into radiant energy.
Changes Between Forms of Energy
(cont.)
radiant
Science Use transmitted by
electromagnetic waves
Common Use bright and shining;
glowing
Changes Between Kinetic
and Potential Energy
Energy changes between
kinetic energy (KE) and
potential energy (PE)
when a ball is thrown and
moves upward and then
downward.
• As the ball moves upward,
its speed and kinetic
energy decrease, but the
potential energy is
increasing because the
ball’s height is increasing.
• At the ball’s highest point,
the gravitational potential
energy is greatest, and the
ball’s kinetic energy is the
least.
• As the ball moves
downward, potential
energy decreases. At the
same time, the ball’s
kinetic energy increases.
• When the ball reaches the
player’s hand again, its
kinetic energy is at the
maximum value again.
The Law of Conservation of Energy
According to the law of conservation of
energy, energy can be transformed from
one form into another or transferred from
one region to another, but energy cannot
be created or destroyed.
What is the law of conservation
of energy?
The Law of Conservation of Energy
(cont.)
Friction is a force that resists the
sliding of two surfaces that are touching.
friction
from Latin fricare, means “to rub”
Friction and the Law of
Conservation of Energy
• What happens to mechanical energy
when you apply the bicycle brakes and
the bicycle stops?
• A moving bicycle has mechanical energy.
When you apply the brakes, the bicycle’s
mechanical energy is not destroyed.
Friction and the Law of
Conservation of Energy (cont.)
• The mechanical energy is transformed
into thermal energy. Friction between the
brake pad and the moving wheel
transforms mechanical energy into
thermal energy.
• There is always friction between any two
surfaces that are rubbing against each
other.
Using Energy
• When you use energy, you usually
change it from one form into another.
• All forms of energy can be transformed
into thermal energy.
• During photosynthesis, a plant
transforms the Sun’s radiant energy into
chemical energy that it stores in
chemical compounds.
Using Energy (cont.)
What happens to energy when
it is used?
Using Energy (cont.)
• When energy changes form, some
thermal energy is always released.
• Scientists often refer to thermal energy
that cannot be used as waste energy.
• Whenever energy is used, some energy
is transformed into useful energy and
some is transformed into waste energy.
• Energy can change
form, but according
to the law of
conservation of
energy, energy can
never be created or
destroyed.
• Friction transforms mechanical
energy into thermal energy.
• Different forms of energy, such as
sound and radiant energy, are used
when someone talks on a cell phone.
All forms of energy can be
transformed into what form
of energy?
A. electric energy
B. radiant energy
C. sound energy
D. thermal energy
What term refers to the changes
from one type of energy to
another type of energy?
A. friction
B. potential energy
C. energy transformations
D. law of conservation of energy
During photosynthesis, a plant
transforms the Sun’s radiant
energy into what type of energy?
A. chemical energy
B. electric energy
C. kinetic energy
D. thermal energy
Do you agree or disagree?
3. Energy can change from one form to
another.
4. Energy is destroyed when you apply
the brakes on a moving bicycle or a
moving car.
Thermal Energy on the Move
• What is heat?
• How is thermal energy transferred?
Thermal Energy on the Move
• heat
• convection
• conduction
• radiation
• thermal conductor
• thermal insulator
Heat
• Heat is thermal energy moving from
a region of higher temperature to a
region of lower temperature.
• Objects contain thermal energy, not
heat.
Heat (cont.)
How is heat related to
thermal energy?
Heat (cont.)
• The movement of thermal energy
causes changes in temperature.
• Two objects in contact with each other
at the same temperature are said to be
in thermal equilibrium.
Conduction
Conduction is the transfer of thermal
energy due to collisions between
particles in matter.
Conduction (cont.)
• Conduction occurs in solids, liquids,
and gases.
• When faster-moving particles collide
with nearby particles at slower speeds,
thermal energy is transferred.
• A material in which thermal energy
moves quickly is called a thermal
conductor.
Conduction (cont.)
• Solids are better thermal conductors
than liquids and gases.
• Most metals are excellent thermal
conductors.
Conduction (cont.)
• A material in which thermal energy
moves slowly is a thermal insulator.
• A winter coat filled with an air-trapping
material is a good example of a
thermal insulator.
Convection
Convection is the transfer of thermal
energy by the movement of particles
from one part of a material to another.
convection
from Latin convehere, means
“to carry together”
Convection (cont.)
• Convection occurs in liquids and
gases.
• Convection begins when part of a liquid
or gas becomes warmer than the rest
of it.
• The cooler, denser liquid or gas falls,
pushing the warmer, less dense liquid
or gas to the top.
Radiation
• Radiation is the transfer of thermal
energy from one object to another by
electromagnetic waves.
• Radiation transfers thermal energy
through matter or through space,
where no matter exists.
• Radiation occurs between objects that
are not in contact.
Radiation (cont.)
• All objects give off electromagnetic
waves, but most are not visible.
• Extremely hot objects emit visible light.
• Electromagnetic waves carry energy
and radiation transfers this thermal
energy from objects at higher
temperatures to objects at lower
temperatures.
Radiation (cont.)
• This hat, coat, and scarf are thermal
insulators because thermal energy
moves slowly through them.
• The transfer of thermal energy by the
movement of particles from one part of
a material to another
is convection.
• The transfer of
thermal energy by
electromagnetic
waves is radiation.
Which term describes the transfer
of thermal energy due to collisions
between particles in matter?
A. conduction
B. convection
C. insulation
D. radiation
Which term describes a material
in which thermal energy moves
quickly?
A. particle
B. convection current
C. thermal conductor
D. electromagnetic conductor
Radiation is the movement
of energy by which of these?
A. conduction
B. convection
C. electromagnetic waves
D. particles in motion
Do you agree or disagree?
5. Warm water sinks below cool water
when they are in the same container.
6. Wearing a coat slows the loss of
thermal energy from your body.
Key Concept Summary
Interactive Concept Map
Chapter Review
Standardized Test Practice
Energy is the ability to
cause change. Energy
transformations occur
when one form of
energy changes into
another form of energy.
Energy is conserved
during energy
transformations.
Lesson 1: Forms of Energy
• Energy is the ability to
cause change.
• Kinetic energy is the energy
a body has because it is
moving. Potential energy
is stored energy.
• Work is the transfer of energy that occurs when a
force makes an object move in the direction of the
force while the force is acting on the object.
• Different forms of energy include thermal energy
and radiant energy.
Lesson 2: Energy Transformations
• According to the law of
conservation of energy, energy
can be transformed from one
form into another or transferred
from one region to another,
but energy cannot be created
or destroyed.
• Friction transforms mechanical energy into thermal
energy.
• Different types of energy are used in many ways
including providing energy to move your body, to
light a room, and to make and to receive cell phone
calls.
Lesson 3: Thermal Energy on the Move
• Heat is thermal energy that moves from matter at a
higher temperature to matter at a lower temperature.
• A material through which thermal energy moves
quickly is a thermal conductor.
• There are three ways in
which thermal energy is
transferred—conduction,
convection, and radiation.
Which term describes the ability
to cause change?
A. energy
B. friction
C. motion
D. work
Which type of energy is due to
the motion of particles that make
up an object?
A. thermal energy
B. sound energy
C. radiant energy
D. kinetic energy
What is a force that resists the
sliding of two surfaces that are
touching?
A. friction
B. work
C. kinetic energy
D. waste energy
Most of the chemical energy
used in cars ends up as what kind
of energy?
A. waste energy
B. thermal energy
C. radiant energy
D. electric energy
Which term describes a material
in which thermal energy moves
slowly?
A. particle
B. thermal conductor
C. thermal insulator
D. electromagnetic wave
What term refers to the transfer of
thermal energy by the movement
of particles from one part of a
material to another?
A. conduction
B. convection
C. heat
D. radiation
What is another term for light
energy carried by
electromagnetic waves?
A. electric energy
B. mechanical energy
C. radiant energy
D. thermal energy
Work depends on what two
factors?
A. force and mass
B. mass and distance
C. force and distance
D. speed and mass
Which is true according to the law of
conservation of energy?
A. Energy can be created and destroyed.
B. Energy can be created, but not
destroyed.
C. Energy cannot be created or destroyed.
D. Energy cannot be created, but can be
destroyed.
Friction between a bicycle’s brake
pads and the moving wheels
transforms mechanical energy
into what kind of energy?
A. chemical energy
B. electric energy
C. potential energy
D. thermal energy
What describes thermal energy
moving from a region of higher
temperature to a region of lower
temperature?
A.
B.
C.
D.
conduction
convection
friction
heat