Section One: What is energy? (pg. 374)
•Energy is the ability to cause change
•Any time a change occurs, energy is transferred from
one object to another
Section One: What is energy? (pg. 375)
•
Kinetic energy is the energy an object has due
to its motion. If an object isn’t moving, it does
not have kinetic energy.
•
A faster ball causes more change to occur
than a ball that is moving slowly
•
Kinetic energy increases as an object
moves faster
•
Kinetic energy increases as the mass of the
object increases (see volleyball/bowling ball
example- pg. 375)
Section One: What is energy? (pg. 376)
•
Potential energy is the energy stored in an
object because of its position.
•
Potential energy increases as the mass
and height of the object increases.
Section One: What is energy? (pg. 376)
•
Thermal energy is the sum of the kinetic
and potential energy of the particles in a
material
•
Thermal energy increases as
temperature increases. (hot chocolate
vs cold water- pg 376)
•
Our bodies produce thermal energy;
thermal energy released by chemical
reactions come from chemical energy
Section One: What is energy? (pg. 376)
•
Chemical energy is the energy stored in chemical
bonds. When chemicals are broken apart and
new chemicals are formed, some of this energy is
released. (candle burning example pg. 377)
Section One: What is energy? (pg. 377)
•
.
•
When light strikes something it can be absorbed, transmitted or
reflected.
When light is absorbed by an object and the object
becomes
warmer, the energy is transformed into
thermal energy.
•
Radiant energy is the energy carried by light.
Section One: What is energy? (pg. 379)
.
•
Electrical energy is energy carried by an electric current.
About 20% of the electrical energy used in the
United States is generated by nuclear power plants.
•
Nuclear energy is energy contained in atomic nuclei.
•
Releasing nuclear energy is difficult and can only be
released through complex power plants.
Section Two: Energy Transformations (pg 379)
Mountain biker climbing a hill:
kinetic energy of the bike and rider
potential energy as he moves up the hill
chemical energy in the rider’s muscles
thermal energy
.
Section Two: Energy Transformations (pg 379)
The Law of Conservation of Energy: energy is never created or
destroyed.
The only thing that changes is the form in which the energy appears
.
Section Two: Energy Transformations (pg 380)
Changing Kinetic and Potential Energy
ex:
Tossing a ball in the air; as the ball leaves your hand, most of its
energy is kinetic. As it rises, its kinetic energy decreases but is
replaced by an increase in potential energy as the ball flies higher
in the air.
The total amount of energy remains constant.
.
Section Two: Energy Transformations (pg 381)
Transforming chemical energy
The matter contained in living organisms (biomass) contains
chemical energy. Chemical energy transforms into thermal energy.
.
Section Two: Energy Transformations (pg 383)
Transforming electrical energy
Radio example (pg. 383):
Electrical energy to kinetic energy of speakers to sound energy of air
to kinetic energy of eardrum and fluid to electrical energy of brain
and nerve cells.
.
Section Two: Energy Transformations (pg 383)
Transforming thermal energy
Thermal energy can be transformed into kinetic energy (for example
steam engines)
Thermal energy can be transformed into radiant energy (for example
when a bar of metal is heated to a high temperature, it glows and
gives off light)
.
Section Two: Energy Transformations (pg 384)
Thermal energy moves
Thermal energy can move from one place to another.
Thermal energy only moves from something at a higher
temperature to something at a lower temperature.
Section Two: Energy Transformations (pg 384)
Generating Electrical Energy
A generator is a device that transforms kinetic energy into electrical
energy; a generator converts the kinetic energy of a spinning turbine
into electrical energy.
turbine- set of steam-powered fan blades that spins a generator at a
power plant.
Section Two: Energy Transformations (pg 385)
Section Questions
Section 3: Sources of Energy
• All of the energy we use can be traced to the Sun or to radioactive
atoms in the Earth’s interior
• The amount of energy Earth receives from the Sun is far greater than
the amount generated in Earth’s interior
• Nearly all of the energy we use today can be traced to the Sun
Section 3: Sources of Energy
• Fossil fuels are coal, oil, and natural gas
• Fossil fuels are nonrenewable resources. A nonrenewable resource
is an energy source that is used up much faster than it can be
replaced.
Section 3: Sources of Energy
Nuclear Energy (pg.389)
• To obtain electrical energy from nuclear energy, a series of energy
transformations must occur. (figure 18- pg. 389)
• Nuclear energy is a nonrenewable resource
• Nuclear energy has advantages and disadvantages.
Ex: The waste produced by nuclear power plants is radioactive
and can be dangerous to living things.
Section 3: Sources of Energy
Hydroelectricity
• Renewable resource is an energy source that is replenished
continually
• Hydroelectricity (the potential energy of water that is trapped behind
dams) is the largest renewable source of energy.
• Advantage: largely pollution free
• Disadvantage: disrupts the life cycle of aquatic life
Section 3: Sources of Energy
Alternative Sources of Energy
• New sources of energy that are safer and cause less harm to the
environment are called alternative resources such as wind, solar
energy, and geothermal energy.
Solar Energy
• solar power
• An inexhaustible resource is an energy source that can’t be used up
by humans. The Sun is an inexhaustible source of energy because it
will go on producing energy for billions of years.
• Solar energy is more expensive to use than fossil fuels
• Solar energy can be collected and utilized by individuals using
thermal collectors or photovoltaic collectors.
• geothermal energy
Section 3: Sources of Energy
Energy from the Oceans
Using Tidal Energy
Tidal Energy
Tidal energy is he energy obtained from the rise and fall of the tides.
Tidal turbines act like underwater windmills.
Tidal barrages are special dams that take advantage of the difference
between high and low tides.
Advantage: inexhaustible resource
Disadvantages:
High cost
Only in a few places is the difference between high and low tides large
enough to enable a large electric power plant to be built
Section 3: Sources of Energy
Wind
WInd energy
Wind is a renewable energy resource.
Kinetic energy is converted into electrical energy
Section 3: Review Questions
1. Diagram the energy conversions that occur when coal is formed, then burned
produce thermal energy. Radiant energy from the sun is converted into
chemical energy when coal is formed; chemical energy in coal is converted
into thermal energy and radiant energy when coal is burned.
2. Explain why solar energy is considered an inexhaustible source of energy.
The sun’s energy cannot be used up by humans because the sun will
produce an enormous amount of energy for billions of uears and humans can
use only a small amount of the energy the Sun produces.
3. Explain how a heat pump is used to both heat and cool a building The
ground at several meters’ depth is cooler than the outside air in summer and
warmer than the outside air in winter. Heat can be transferred from the
building to the ground in summer, and from the ground to the building in the
winter.
4. Identify advantages and disadvantages of using fossil fuels, hydroelectricity
and solar energy as energy sources.