TRANSFORMATION OF ENERGY
Unit Readings and Assignments
Name _______________________
Table of Contents
Part 1 : The Flow of Energy
Pages 2-9
Homework Assignment 1
Page 4
Homework Assignment 2
Page 7
Homework Assignment 3
Page 9
Part 2 : Heat Energy
Pages 10-14
Homework Assignment 4
Page 12
Homework Assignment 5
Page 14
Part 3 : Waves
Pages 15-25
Homework Assignment 6
Page 16
Homework Assignment 7
Page 18
Homework Assignment 8
Page 21
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Part 1: The Flow of Energy
Energy is the most central concept in all of science. It is the thread that
ties the physical, life, and earth sciences together. Matter and energy make up
the universe. We commonly say that objects have energy, but we can’t really see
this energy. We recognize energy mainly through
the effects it has on objects. We see things
happen and changes occur when an object or
substance has energy and shares that energy with
other objects.
Energy is not easily defined. So scientists study energy by looking at the
effects it had on other things. A definition that is often used for energy is “the
ability to bring about some sort of change.” If something has energy, then it can
cause a change in itself or in its surroundings. By designing experiments to study
these changes, scientists learn more about energy.
As an object’s speed increased, so does its ability to create change. Also,
the mass of the object is important in determining how much change it can
produce. The ability of a moving object to cause change is important. We have
found that both the speed and mass determine this ability.
In science, we define a quantity that describes how
much change an object can produce as its ‘energy of
motion’, more commonly called the kinetic energy.
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Every moving object such as cars, soccer balls, basketball players, river
water, and even clouds has kinetic energy. If the object has mass and is moving, it
has kinetic energy. Our experiments will show that as the speed and/or mass of
the object increases, its kinetic energy increases too.
We will discover that the higher the ball is released, the greater its kinetic
energy will be at the bottom of the ramp. When the ball is lifted to the top of the
ramp, the energy you use to lift it is stored. As the ramp gets higher and higher,
the golf ball’s stored energy at the top of the ramp gets larger also.
If the ‘stored’ energy at the top of the ramp gets larger, the kinetic energy
of the ball at the bottom of the ramp will get larger too. Where did the ‘stored’
energy come from? It came from you, or whoever lifted the ball to the top of the
ramp. The ball will not roll up the ramp by itself. It must be lifted upwards to the
top of the ramp, because gravity pulls downward on everything.
The lifting process requires
energy, and the energy you use to
lift the ball is stored by gravity.
We can think of the energy in
We call this energy stored
by gravity Gravitational
Potential Energy (GPE).
our food being transferred to the
ball by our muscles, and transformed by gravity into stored energy. When the ball
is released, this stored energy is transformed into kinetic energy, and the ball
begins moving down the ramp with greater and greater speeds.
In summary, two important forms of energy are:
Kinetic Energy (KE), the energy an object has because of its motion, which is
determined by the object’s mass and speed.
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Gravitational PE, the stored energy an object has because it was lifted to
some height. This potential energy is determined by the object’s mass and
its height above the ground.
Two important properties of energy are:
Energy transfer is the passing of the same form of energy from one object
to another.
Energy transformation is the changing of energy from one form to another.
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Homework Assignment # 1
Speed limits are a fact of life when driving on roads throughout the state.
Various roads/highways have very different speed limits. You will learn in your
drivers’ education courses that speed limits are posted for the protection of the
driver and passengers in the vehicles, as well as for pedestrians near the
roadways.
Typical speed limits (in miles per hour) in our state are:
65 mph on Route 1
50 mph on country roads through farmland
35 mph on roads through residential areas
25 mph on roads in busy sections of cities and towns
20 mph for large trucks in sections of cities and towns
Use your knowledge of kinetic energy to explain why different speed limits are
needed, depending on the road and the size of the vehicle, to help protect the
safety of the citizens in Delaware’s cities and towns. (You answer should be more
than a one sentence explanation.
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Particle Model
An important goal of this unit is to establish that when objects slide,
bounce, or roll to rest, that their kinetic energy does not just disappear. This
energy is transferred to the tiny particles that make up the objects involved. The
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model that best describes the behavior of these particles is called the Particle
Model.
Key Ideas about the particle model:

The particles of a single substance are the same, whether the substance is a
solid, liquid or gas. Only the nature of the connections between particles
changes when the phase of the substance changes.

Particles are always moving (even in solids).

Particles in solids vibrate around a fixed position. These connections are
strong and keep the particles closely packed together.

Particles in liquids move more freely than do solids. The connections
between particles in a liquid are weaker than in a solid, but strong enough to
keep the particles close together.

Particles in gases are moving freely and move as far apart from each other
as their container allows.

Adding energy, like heat, causes the particles to move more quickly and
further apart.
Adding energy will not change the size of the particles, but the total volume
will tend to increase as the particles move away from one another as they vibrate
more and more. Here are two visuals…
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Figure 1: The passengers on the bus are like particles in solids; they can move around a little, but are
confined by the seats and others around them. The incoming passengers are like liquids; they have more
freedom to move, but are bound by the door opening and aisle. The exiting passenger is like a gas; he is
free to move around in many directions and has few restrictions on his movement.
Figure 2: The picture above show the vibrations of the particles in a solid, liquid, and gas. The solid
particles can not vibrate much without touching one another, but the gas particles have much more room
to vibrate before touching one another.
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Homework Assignment # 2
Draw another representation (picture) of the particle like the two examples on
the previous page. Then, describe what happens to the particles as the energy of
a substance or object is increased.
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ENERGY CHAINS
Understanding how energy flows can be very helpful. It can help you explain
many things in our everyday life.
Objects transfer energy to other objects by pushing or
pulling on them. In science, we say that objects transfer energy
through the application of forces.
Forces, such as gravity, friction between sliding surfaces and the forces of
collision, are responsible for energy transfer from one object to another. They
also cause the transformation of energy from one type to another.
What is an energy chain?
In our everyday life, energy is transferred and transformed all the time. It
is helpful to be able to track the ‘flow’ of energy in our everyday life. A map of
what happens to the energy, where it goes, and how it changes, is called an energy
chain.
A good chain should include the forms of energy and any transfers or
transformations that happen in the example. It is also be helpful to identify a
starting point and an ending point.
Heat Energy – The Graveyard of Energy
You may have already noticed that heat energy is almost always the form
taken by the energy at the end of an energy chain. It happens so often that
scientists refer to heat as the “graveyard of energy”. Every energy chain should
include the transformation to Heat Energy every time and energy transformation
takes place.
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Homework Assignment #3
You have now seen several experiments that involve the transfer and
transformation of energy. Draw an energy chain detailing one of these
experiments.
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Part 2: Heat Energy
Thermometers, and other temperature sensing devices, measure the energy
of the particles of water in contact with the thermometers’ probe. (We will look
more closely at this interpretation of temperature in the activities that follow.)
The sensors in your skin detect the transfer of energy into or out of your skin.
The temperature of an object and how it feels when you touch
it are related, but they are not the same. The temperature of an
object is related to the motion of its particles. Hot and cold are
sensations that we feel. These sensations are based on more
than temperature and can vary from person to person. Put it this
way…
o Whenever heat energy is being transferred into your skin, the sensors
signal that whatever you are touching is warmer than your skin. If
large quantities of heat energy are transferred into your skin quickly,
the message you will get is hot!!!
o If heat energy is being transferred away from your skin, the same
sensors signal that the object is cooler than your skin.
When your
skin signals cold!!! it is because large quantities of heat energy are
quickly leaving your skin.
 The sensors in your skin detect heat energy transfer, not temperature. Heat
is always transferred from the hotter object to the colder object.
Heat Energy
HOT OBJECT
COLD OBJECT
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So what does the temperature of an object represent?
The temperature of an object is linked to something much more fundamental
than hot or cold. The temperature of an object tells us about the energy of its
particles. When the particles are more energetic, the temperature of a substance
is higher. When the particles of a substance are less energetic, the substance is
at lower temperatures. Thermometers are designed to detect the energy of the
particles, not whether the substance feels hot or cold.
We know from the Particle Model, that all objects and substances are
made from tiny particles. These particles that make up an object are always in
motion, even when the object itself is not. Since these particles are moving, they
have kinetic energy. The total kinetic energy of these particles is called the heat
energy. By looking at the graph below, you should see the relationship between
temperature and heat energy.
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Homework Assignment #4
1. Joe and Bob are riding their bicycles down the neighborhood street. As they
approach the end of the block a construction worker motions for them to stop,
so they both slam on their brakes and skid to a stop. Joe says “Whew, with all
of that energy we had, I’m surprised that we were able to stop.” Bob agrees
and says, “it’s a good thing that there was a lot of friction between our back
tires and the sidewalk.” As the boys are discussing the matter, the
construction worker points out that some of their back tires’ tread has been
scrapped off during the skid, leaving tiny bits of rubber on the sidewalk behind
them and a skid mark.
Describe how the sliding friction force transformed the bike’s kinetic energy
into heat energy. What evidence could the boys collect to justify this stance?
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2. During winter, a coat helps to ‘keep us warm’. Use what you just learned
about the sensations of hot and cold to explain how a coat keeps you warm on a
cold winter’s day.
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Heat Energy Transfer
Conduction
Conduction is the transfer of heat through direct contact between two
objects or environments for example, heating a pot over a burner is an example of
conduction.
Convection
Convection is the transfer of heat through the movement of fluids, such as
air or liquids, at different temperatures. This transfer of heat is not due to
individual molecular motion, as in conduction; rather, it is due to the macroscopic
motion of a collection of molecules.
Boiling water is an example of heat transfer due to convection. If water is
heated in a pot on a burner, the warm water will rise to the top and the cold water
falls. However, the cold water at the bottom of the will eventually be heated, and
rise to the top, leading to continuous motion of the water, which increases the
temperature throughout the water.
Radiation
Radiation is the transfer of heat energy through electromagnetic radiation,
e.g., infrared light or visible light. This transfer of energy can occur through empty
space.
The heating of the Earth by the Sun is an example of heating due to
radiation. The Sun emits great amounts of energy in the form of electromagnetic
radiation, some of which is absorbed by the Earth, leading to an increase in the
Earth's temperature.
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Homework Assignment #5
Draw a picture that show the three forms of heat energy transfer without using
any words
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Part 3: Waves
What Are Waves?
How many waves do you actually see? The chances are you do not see any
waves at all. You might know that if you can hear, the sounds you hear were
vibrational energy carried to you in the form of a wave. A big part of the problem
with investigating waves is the fact that we cannot see the waves that are most
important to us.
When asked to visualize waves, most of us think of disturbances on the
surface of water. We think of the ripples on the water’s surface when we throw a
stone into a pond, or we think of crashing mounds of water at the seashore. If we
were asked to draw a sound wave or light wave, we could not use the
information we hear or see to help us sketch the waves, because we
have never seen these waves.
Waves are disturbances that carry energy. These disturbances are highly
organized, and if you could see them, it would be easy to see patterns as the waves
passed in front of you. All waves require coordinated vibrations to travel.
Sometimes these vibrations are the organized motions of particles that make up
materials, but sometimes the vibrations do not involve particles of matter at all.
Waves have no mass, and mass never moves along with a wave. This may
seem confusing because many waves that pass through matter make the particles
vibrate in a coordinated way. The particles do vibrate back and forth, but they do
not move along with the wave.
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Transferring Energy – Moving Mass or Waves?
 When energy is carried by moving mass, it takes the form of the kinetic
energy of the moving matter. Energy is transferred
when mass moves from the source of energy to the
place where the energy is delivered.
 When waves carry energy, there are organized
vibrations that move from the source of energy to
the place where energy is delivered, but no matter
travels along with the waves.
Home Work Assignment #6
Ammie is out for a jog, and brings her portable radio along. She turns on the
radio and listens to her favorite station as she runs. What are the different
kinds of energy are needed for Ammie to hear a song being played on a local
FM station? How many of these forms of energy are transferred through the
action of waves?
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HOW DO WE GROUP WAVES?
There are many different kinds of waves. To make it easier to understand
waves, we divide them into groups that have similar properties. These properties
involve the way the waves carry energy, and the type of energy carried by the
waves.
HOW DO WAVES CARRY ENERGY?
All waves are disturbances that carry energy from one region to another.
Some waves can only travel through matter. These waves travel by causing
organized vibrations of particles in matter. We group these waves together and
call them Mechanical Waves.
Other waves travel by causing vibrations that do not involve particles.
These waves can travel through matter, but they can also travel through the
vacuum of empty space. We call this group of waves Electromagnetic Waves.
WHAT FORMS
OF
ENERGY DO
THE
TWO GROUPS
OF
WAVES CARRY?
Another way of looking at the difference between these two groups of
waves is to look at the type of energy carried by each group. Mechanical waves can
only carry mechanical energy (mainly KE), and electromagnetic waves can only carry
electric energy and magnetic energy.
A mechanical wave begins when something pushes or pulls on a substance
forcing its particles to vibrate in an organized manner. When a mechanical wave is
moving through a substance, the particles move in a very coordinated and
predictable way.
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Longitudinal Waves and Transverse Waves
Mechanical waves can involve two types of vibrations. If the particles
vibrate back and forth along a line that is parallel to the direction in which the
wave moves, the wave is called a Longitudinal Wave. If the particles vibrate in a
direction that is perpendicular to the line along which the wave moves, the waves
are called Transverse Waves.
Mechanical waves in solids can be longitudinal waves or transverse waves. In
liquids or gases, only longitudinal mechanical waves are possible. All
electromagnetic waves are transverse waves.
Homework Assignment #7
Suppose you are sitting outside, and you hear the buzzing of a bee visiting a
nearby flower. Make a detailed energy chain that describes how the kinetic
energy of the bees wings results in a buzzing sound in your head. Make sure
you identify:
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MECHANICAL WAVES
There are many different kinds of mechanical waves. To better understand
their properties, we sort mechanical waves into groups using a concept called
frequency. We know that mechanical waves involve the vibrations of particles in
matter. The frequency of a mechanical wave is determined by how quickly the
particles vibrate.
The frequency of a mechanical wave that travels
through a substance is equal to the number of vibrations
completed every second by the particles in the substance.
The most important mechanical waves in our
lives are the waves that carry energy that
activates our sense of hearing. If longitudinal
mechanical waves have frequencies that are
greater than 20 vibrations per second, but less
than 20,000 vibrations per seconds, they will
trigger our sense of hearing much like heat energy triggers our sense of touch.
For this reason, we say we can ‘hear’ mechanical waves that have frequencies
between 20Hz and 20,000Hz. Low frequency waves will sound like low pitch tones.
As the frequency of the waves increase, the pitch of the sounds we hear when
those waves enter our ears will increase as well.
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ELECTROMAGNETIC WAVES
HOW DO ELECTROMAGNETIC WAVES COMPARE
TO
MECHANICAL WAVES?
We have learned that the organized vibrations of particles in matter cause
mechanical waves. If there are no particles to vibrate, there will be no mechanical
waves. This is why mechanical waves must travel through matter, and cannot travel
through the vacuum of empty space.
There are similarities between electromagnetic waves
and mechanical waves.
 Electromagnetic waves carry
energy, but do not transport
matter.
 Electromagnetic waves can be
described in terms of frequency,
wavelength, and wave speed.
 Electromagnetic waves can travel through matter.
But there are very important differences between
electromagnetic waves and mechanical waves too.

Mechanical waves carry mechanical energy (mainly KE), but electromagnetic
waves carry electric energy and magnetic energy.

Mechanical waves result in the organized vibration of particles, but
electromagnetic waves can travel where there are no particles. If fact, it
can be argued that electromagnetic waves travel best through the vacuum of
free space.
***All electromagnetic waves travel much faster than mechanical waves.***
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Homework Assignment#8
Create a Venn Diagram for Mechanical and Electromagnetic Waves.
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The wavelengths of
electromagnetic waves range from
very large distances to extremely
tiny distances. Some
electromagnetic waves have
wavelengths longer than the State
of Delaware. Other waves have
wavelengths that are so small that it one of these waves would need to be millions
of wavelengths long to stretch across this little circle → ◦ (that’s a pretty short
wavelength!). Pick any distance between 1/10,000,000 of a centimeter and
hundreds of kilometers, and there are electromagnetic waves that have
wavelengths equal in length to that distance.
The wavelength and frequency of a wave are related mathematically, so it does
not really matter which characteristic is used to group the waves. In fact, some
electromagnetic waves, especially radio waves, are described by their frequency.
As was described above, wavelengths of electromagnetic waves range from
hundreds of miles long to unimaginably tiny distances. This range is so broad that
electromagnetic waves are divided into seven (7) smaller groups; radio waves,
microwaves, infrared waves, visible light, ultraviolet light, X-rays, and gamma rays.
Collectively, these seven groups of waves make up the electromagnetic spectrum.
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Electromagnetic waves that have wavelengths roughly five ten millionths
(that’s 5/10,000,000) of a meter long make up the group of waves called visible
light. Numbers that small are difficult to grasp. Put differently, it would take a
visible light wave roughly 2,000 wavelengths long to reach across this circle◦.
THE ELECTROMAGNETIC SPECTRUM
Visible light represents far less than 1/7 of the electromagnetic spectrum.
In fact, it is the narrowest range of wavelengths of all of the seven groups of the
electromagnetic waves. They are singled out for one single reason; humans have
eyes that are sensitive to the energy carried by electromagnetic waves that have
wavelengths in this range. We see objects because light leaves those objects and
enters our eyes. Light must enter our eyes for us to ‘see’.
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DO VISIBLE LIGHT WAVES CARRY COLOR?
No waves carry “color”, only energy. Human eyes have two types of
receptors. One of these types of receptors is especially sensitive but it cannot
easily distinguish between the different wavelengths of visible light. These are
the receptors we use in low light conditions, at night for instance.
The other type of receptor is sensitive to differences in the wavelengths of
visible light. The energy carried by the different wavelengths of visible light
stimulates these receptors differently. We see these differences as colors. The
shorter wavelengths are the blue and violet colors, and the longer wavelengths are
the reds and orange colors. In between, the medium wavelengths create the
sensation of the yellow and green colors.
The visible light waves are not colored. Electromagnetic waves have no color
at all. The energy carried by visible waves can stimulate some of the receptors in
your eyes to
produce the
sensation of color.
But not all eyes
have these
receptors.
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Can Eyes Detect Color?
Many animals are incapable of seeing colors. The waves entering their eyes
carry suitable energies, but there are none of the receptors in their eyes that are
sensitive to the differences in the wavelengths in visible light. Animals that lack
these receptors in their eyes see the world in black, grays, and white.
There are other animals that can see in color, even wavelengths outside of visible
light. Some insects have eyes that are sensitive to ultraviolet waves. Moths and
some flowers that appear bland in color in visible light, look very colorful to insects
that have eyes that are sensitive to ultraviolet light.
How does the energy carried by a wave get delivered to a substance?
When a wave strikes the surface of a substance, part of the wave will
reflect off of the surface and the other part will pass through the surface and
enter the substance. The reflected part of the wave carries its energy away from
the surface and never enters the substance. The part of the wave that enters the
substance will either pass right through the substance or become absorbed by the
particles in the substance.
Often it does both. The transmitted part of the wave carries its energy out
of the substance. The only part of the wave that actually delivers energy to the
substance is the part that is absorbed. Its energy is transformed into another
form that is usually (but not always) heat energy.
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