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PRENTICE HALL SCIENCE EXPLORER
PHYSICAL SCIENCE
CHAPTER 13
ENERGY
13-1 What Is Energy?
Objectives:
• Explain how energy and power are related.
• Give examples of two basic kinds of energy.
A. Energy, Work, and Power
1. The ability to do work or cause change is called energy.
2. Energy and work are transferrable.
3. Both energy and work are measured in joules.
4. Power is the rate at which work is done.
5.
B. Kinetic Energy
1. The energy an object has due to its motion is called kinetic energy.
2. The word kinetic comes from the Greek word kinetos, which means
“moving.”
3. Kinetic energy depends on both an object’s mass and velocity.
4.
5. Kinetic potential energy increases as mass and velocity increase.
C. Potential Energy
1. Stored energy that results from the position or shape of an object is called
potential energy.
2. Potential energy related to an object’s height is called gravitational potential
energy.
3.
4. Gravitational potential energy increases as weight and height increase.
5. The potential energy associated with objects that can be stretched or
compressed is called elastic potential energy.
13-2 Forms Of Energy
Objectives:
• Explain how you can determine an object’s mechanical energy.
• Tell the forms of energy associated with the particles that make up objects.
A. Mechanical Energy
1. The form of energy associated with the position and motion of an object is
called mechanical energy.
2. An object’s mechanical energy is a combination of its potential and kinetic
energy.
3.
B. Other Form of Energy
1. Thermal Energy – is the total potential and kinetic energy of the particles of
an object.
2. Electrical Energy – is the energy of electric charges.
3. Chemical Energy – is the potential energy stored in the chemical bonds that
hold chemical compounds together.
4. Nuclear Energy – is the potential energy stored in the nucleus of an atom.
5. Electromagnetic Energy – is the energy that has some electrical properties and
some magnetic properties and travels in waves.
a.) Light
b.) Microwaves
c.) Radio waves
d.) X-rays
e.) Gamma waves
13-3 Energy Transformations And Conservation
Objectives:
• Explain how different forms of energy are related.
• Give an example of a common energy transformation.
• Tell what the Law of Conservation of Energy is.
A. Energy Transformations
1. Most forms of energy can be transformed into other forms of energy.
2. A change from one form of energy to another is called an energy
transformation.
3. Single Transformations – are transformations where one form of energy is
transformed into another form of energy.
a.) A toaster transforming electrical energy into heat energy is a single
transformation.
b.) Your body transforming chemical energy from food into mechanical
energy is a single energy transformation.
4. Multiple Transformations – are a series of transformations that take place in a
system to accomplish a job.
a.) Striking a match: mechanical → chemical →heat.
b.) Powering a car: chemical → heat → mechanical.
B. Transformation Between Potential and Kinetic Energy
1. One of the most common energy transformations is the transformation
between potential energy and kinetic energy.
a.) Energy Transformation in Juggling.
b.) Energy Transformation in a Pendulum.
c.) Energy Transformation in a Pole Vault.
C. Conservation of Energy
1. The Law of Conservation of Energy States: When one form of energy is
transformed into another, no energy is destroyed in the process.
2. According to the Law of Conservation of Energy, energy cannot be created or
destroyed.
3. Energy and Friction – Friction transforms mechanical energy into heat energy.
4. Energy and Matter
a.) According to Einstein’s theory of relativity, matter can sometimes be
transformed into energy.
b.) Transforming a small amount of matter into energy results in a huge
amount of energy.
c.)
13-4 Energy And Fossil Fuels
Objectives:
• Explain the source of energy stored in fossil fuels.
• Explain how energy is transformed when fossil fuels are burned.
A. Formation of Fossil Fuels
1. Fuels such as coal, petroleum, and natural gas are known as fossil fuels.
2. Fossil fuels come from remains of ancient plant and animal life on Earth.
3. Fossil fuels contain energy that came from the Sun.
4. Fossil fuels are non-renewable meaning that they are used up faster than they
can be replenished.
B. Use of Fossil Fuels
1. Fossil fuels can be burned to release the chemical energy stored in the remains
of the ancient plants and animals.
2. The process of burning fuels is known as combustion.
3. 86% of the energy used on Earth at this time comes from combustion of fossil
fuels.
4. In an electrical generation plant:
a.) Fossil fuels are burned to produce high pressure steam.
b.) The high pressure steam is used to turn turbines.
c.) The turbines are used to turn generators.
d.) The generators produce electricity that is sent to homes and industry by
wires in the power grid.
e.) The electrical energy is then transformed into mechanical or thermal
energy for use by the consumer.
5. The combustion of fossil fuels introduces a huge amount of pollution into our
environment.
6. The use of fossil fuels in also very expensive because it is in limited supply.