Download Lesson 1 What Are Some Forms of Energy? Fast Fact A Balancing

Lesson 1
What Are Some Forms of Energy?
Fast Fact
A Balancing Rock This rock formation, an example of a pedestal rock or balancing rock, was
formed as a result of erosion. A rock this big can have a mass of more than 1000 kilograms
(more than I ton). This gives the top of a pedestal rock a lot of potential energy. In the
Investigate, you will see how potential energy may be changed into kinetic energy.
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Changing Energy
Materials
 board (about 1 m long)
 metric ruler
 5 books of about equal thickness
 4-wheeled cart
 meterstick
Procedure
1. Choose a smooth area of the floor with at least 2 m of clear space. Place the board on the
floor; and put a book under one end of the board.
2. Lay the meterstick on the floor at the end of the board, beside the path the cart will take
after it has rolled down the board. Copy the data table.
3. Measure and record the height from the floor to the top of the board.
4. Hold the cart so that its back wheels are at the top edge of the board. Let the cart go, but do
not push it.
5. Measure and record the distance the cart travels along the floor from the lower edge of the
board. Also record the speed of the cart (slow, medium, or fast).
6. Add another book to raise the high end of the board more. Repeat Steps 3 through 5.
Continue adding books and repeating Steps 3 through 5 until you have used all five books.
Draw Conclusions
1. How did the height of the starting point affect the distance the cart traveled along the floor?
How did it affect the speed of the cart?
2. Inquiry Skill Identify the variables you used in this experiment. Which variables did you
control? Which variables did you change?
Investigate Further
Does the mass of a cart affect how much energy it has? Design an experiment for
observing how mass affects energy.
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Reading in Science
VOCABULARY
energy p. 150
potential energy p. 150
kinetic energy p. 150
law of conservation of
energy p. 154
SCIENCE CONCEPTS
 what kinds of energy there are
 how energy changes from one form to another
READING FOCUS SKILL
MAIN IDEA AND DETAILS Look for examples of kinds of energy and energy changes.
Potential and Kinetic Energy
Have you ever gone skiing? Imagine standing on your skis at the top of a ski slope. You take a
deep breath and push off with your ski poles. At first you move slowly. Then you gain
speed, gliding faster and faster over the snow. This motion takes energy, but you are not
supplying it. Where does the energy come from?
Energy is the ability to cause change in matter. Energy moves you up the hill on the ski lift.
Energy moves you down the hill on your skis.
As you move higher and higher up the hill, your potential energy becomes greater and greater.
Potential energy is stored energy that is due to the position or condition of an object. You
have a lot of potential energy when you are at the top of the hill. When you begin to ski
down the hill, your potential energy changes into kinetic energy, the energy of motion. By
the time you reach the bottom of the hill, almost all of your potential energy has changed
into kinetic energy.
The amount of potential energy an object has depends on its position and its mass. A thick
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layer of snow at the top of a mountain has a huge amount of potential energy because it is so
high. If that snow mass begins to slide down the mountain in an avalanche, its potential
energy quickly changes into kinetic energy. The faster the snow moves downhill, the more
kinetic energy it has. The moving snow has
so much kinetic energy that it can destroy buildings and trees in its path.
Energy has different forms. You use many of them each day. For example, you use electrical
energy when you turn on a lamp to produce light. You use thermal energy when you make
toast. You produce sound energy when you play music.
Energy changes things. Think about things you use that run on electrical energy. You run
on energy, too. The chemical energy in the food you eat keeps your body moving and
working.
MAIN IDEA AND DETAILS What are four Skills forms of energy?
---see picture pg.150
At the top of the hill, the skier has a lot of stored or potential energy. As the skier skis
down the hill, his potential energy changes to kinetic energy.
---see pictures pg151
An avalanche devastated this village at the base of a mountain.
In an avalanche, the potential energy of the mass of snow and ice becomes kinetic energy
as the mass rushes down the mountain.
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Energy Transformations
Fireworks light up the night sky. Red, blue, green, and gold sparks twinkle in the dark. The
crowd gasps as a bright flash is followed by a loud bang.
When you watch a fireworks display, you're watching a series of energy transformations. One
form of energy can be transformed into many other forms of energy. In fireworks, the
energy transformations begin as stored chemical energy in a rocket. Different chemicals
are packed into the rocket in layers so that their chemical energy will be used in sequence.
First, a chemical reaction produces energy that pushes the rocket high into the sky—
potential chemical energy is transformed into kinetic energy.
When the rocket is high in the sky, more chemical reactions cause the colored sparks.
Another reaction releases the bright flash that is followed by the bang as chemical energy is
changed into light and sound energy. Some of the chemical energy also changes into
thermal energy. You don't want to be close enough to feel this!
Chemical potential energy can be stored in a battery. When you turn on a flashlight, chemical
potential energy is changed into electrical energy. The electrical energy is then changed
into light energy, and the bulb shines.
Think about the energy changes that take place when food is cooked. In a toaster, electrical
energy is changed into thermal energy, which is transferred as heat. The heat causes a
change in the bread, making it warm, brown, and crisp. If you look into the toaster while it
is turned on, you can see that the
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wires glow. This is because some of the electrical energy is changed into light energy.
Where does the electrical energy used by the toaster come from? Your home is connected to a
system of electrical lines and cables that lead to a generating station. There, electrical
energy is generated, or produced, from an energy source.
At some generating stations, electrical energy is produced by using the energy of moving water.
Water held behind a dam has potential energy because of the height of the water. When the
water flows down through the gates in the dam, its potential energy becomes kinetic
energy.
At other generating stations, a fuel, such as oil, is burned. The chemical energy in the fuel is
changed first into thermal energy, which changes liquid water into steam that turns large
turbines, and finally into electrical energy. Some plants use nuclear energy to generate
electrical energy. Nuclear energy is energy produced by nuclear reactions—the addition or
emission of neutrons to or from the nucleus of an atom.
Solar energy, the energy of the sun, can also be transformed into electrical energy. You may
have seen solar panels on water heaters, swimming pools, and even experimental cars.
These panels absorb the sun's energy and change it into electrical energy.
MAIN IDEA AND DETAILS What are three forms of energy that can be changed into
electrical energy?
Insta-Lab
How Does Energy Change?
Turn on a personal CD or cassette tape player. Make a list of the forms of energy you observe
as you do this. What energy transformations take place?
---see picture pg.152
Fireworks use a series of energy transformations to produce brilliant displays of light and
color.
---see pictures pg.153
What energy transformations take place in a toaster oven and in a flashlight?
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Law of Conservation of Energy
You see the flash of lightning, and you hear the rumble of thunder. If you're inside a
building, you may notice the windows rattling. Many energy transformations happen
during a thunderstorm.
Lightning is electrical energy moving between clouds or between a cloud and the ground. Some
of this energy changes into light energy, which you see as the flash. Some changes into
sound energy, which you hear as the thunder. The waves of sound energy change into
kinetic energy when they meet an object, moving the tiny bones inside your ears or rattling
the windows in their frames.
If lightning reaches Earth, some of its electrical energy changes into thermal energy. Heat from
lightning can melt sand on a beach, split a tree in two, or set fire to a forest.
The many energy transformations that take place during a thunderstorm demonstrate the law of
conservation of energy. The law of conservation of energy states that the total amount of
energy in a system is always the same—energy cannot be created or destroyed. No energy
is lost during a thunderstorm, and no new energy is produced. Energy just changes forms.
MAIN IDEA AND DETAILS What is the most important idea of the law of conservation
of energy?
A lightning flash transfers energy between clouds or from clouds to Earth.
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Reading Review
1. MAIN IDEA AND DETAILS Draw and complete the graphic organizer.
2. SUMMARIZE Write three sentences that tell what this lesson is mainly about.
3. DRAW CONCLUSIONS In many generating stations, a fuel such as oil is burned as a
source of energy. What energy transformation takes place in the process?
4. VOCABULARY How are potential energy and kinetic energy different?
Test Prep
5. Critical Thinking What energy transformations take place when you use an electric fan to
cool a room?
6. Which kind of energy is stored in a battery?
A. chemical
B. heat
C. kinetic
D. light
Writing
Descriptive Writing
Write a description of what it feels like to go back and forth and up and down on a swing.
Describe how potential and kinetic energy change as you ride the swing.
Math
Write Equations
A liter of water that has a temperature of 45°C is mixed with a liter of water that has a
temperature of 25°C. Which of the following equations shows the temperature of the
mixture?
a. 45° + 25° = 70°
b. 45° - 25° = 20°
c. (45° + 25°) ÷ 2 = 35° F
Art
Energy Collage
Look through magazines and newspapers to find pictures that represent ways you use energy
every day. Use the pictures to make a collage on a small sheet of poster board.
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