Energy Transfers and
Transformations
• What is the law of conservation of
energy?
• How is energy transformed and
transferred?
• What are renewable and
nonrenewable energy resources?
Energy Transfers and
Transformations
• law of
conservation
of energy
• energy transfer
• energy
transformation
•
•
•
•
work
open system
closed system
renewable energy
resource
• nonrenewable
energy resource
Law of Conservation of Energy
The law of conservation of energy says
that energy can be transformed from one
form to another, but it cannot be created or
destroyed.
In every energy transformation, some
energy transfers to the environment.
The radiant
energy that shines
out of the
flashlight cannot
be greater than
the chemical
energy stored in
the battery.
Law of Conservation of Energy (cont.)
• When energy moves from one object
to another without changing form, an
energy transfer occurs.
• The mechanical energy of a tennis
racket changing the movement of the
ball is an example of an energy transfer.
• Come up with your own example of an
energy transfer with your partners
Law of Conservation of Energy (cont.)
• When one form of energy is converted
to another form of energy, an energy
transformation occurs.
• The conversion of chemical energy
stored in a tennis player’s muscle
changing to mechanical energy when
she swings her arm is an example of an
energy transformation.
• Come up with your own example of an
energy transformation with your partners.
Law of Conservation of Energy (cont.)
Identify an energy transfer and an
energy transformation that occurs
when someone plays a guitar.
Law of Conservation of Energy (cont.)
Identify an energy transfer and an
energy transformation that occurs
when someone plays a guitar.
Answer: Chemical energy in the cells is
transformed to mechanical energy in the
fingers, then transferred to the guitar strings.
Electric energy from the amp is converted into
sound energy when the chords are struck.
Law of Conservation of Energy (cont.)
• To a scientist, work is the transfer of
energy that occurs when a force makes
an object move in the direction of the
force.
• Work is only being done while the force
is acting on the object.
• Any time there is an energy
transformation or energy transfer, some
energy is transformed into thermal
energy.
• If a tennis player is holding a tennis ball
before a serve, is she doing work on the
ball?
– Recall that to do work a force must be
working on an object.
• Come up with an example of work
being done in your everyday life, with
your partners.
• Anytime there is an energy transformation
or energy transfer, some energy is
transformed into thermal energy.
• Energy transformations are inefficient
because not all the energy that is
transformed to another form of energy is
usable.
• Lets go back to the flashlight. In a
flashlight the transformation of chemical
energy from the battery to radiant energy
from the light bulb is inefficient. As the
electric energy move through the circuit,
some electric energy transforms to thermal
energy. This makes the transformation
inefficient, and this is why some bulbs are
warm.
• With your partners: Explain the above
transformation and why its inefficient.
Systems
• An open system is a system that
exchanges matter or energy with the
environment.
• A closed system is a system that does
not exchange matter or energy with the
environment.
• In reality, there are no closed systems
because every physical system transfers
some energy to or from its environment.
Renewable Energy Resources
• A renewable energy resource is an
energy resource that is replaced as fast
as, or faster than, it is used.
• Solar energy from the Sun is one type of
renewable energy resource that can be
converted into electric energy.
Renewable Energy Resources (cont.)
• Wind moves the blades of a wind turbine
to generate electric energy.
• In hydroelectric plants, falling water is
channeled through a turbine which
transforms mechanical energy into
electric energy.
Renewable Energy Resources (cont.)
• Geothermal plants transfer thermal
energy from the Earth to water, creating
steam that turns turbines in electric
generators. (click me)
• Biomass includes wood, plants, manure,
and garbage, all of which are sources of
stored chemical energy that can be
transformed to electric energy in energy
plants.
Nonrenewable Energy Resources
• Nonrenewable energy resources are
energy resources that are available in
limited amounts or that are used faster
than they can be replaced in nature.
• Fossil fuels include petroleum, natural
gas, propane and coal.
• In nuclear energy plants, uranium atoms
are split apart in a process called nuclear
fission.
Most of the energy used in the United
States comes from nonrenewable energy
resources.
What are renewable and
nonrenewable energy resources?
What are renewable and
nonrenewable energy resources?
Renewable: energy resource that is replaced
as fast or fast than it is used
Nonrenewable: energy resource that is
available in limited amounts or is used faster
than can be replaced in nature
• Energy can be transferred and
transformed, but it cannot be created
or destroyed.
• Systems are classified as open
systems or closed systems based on
their interactions with their
environment.
• Energy resources are classified as
renewable or nonrenewable based
on their abundance and availability.
1. Which term refers to the
transfer of energy that occurs
when a force makes an object
move in the direction of the
force?
A. conservation
B. work
C. closed system
D. open system
2. A car’s engine is an example of
which of these?
A. closed system
B. energy resource
C. geothermal energy
D. open system
NOW what do you think?
Do you agree or disagree?
1. In most systems, no energy is
transferred to the environment.
2. Some forms of energy are replenished
naturally.
3. Which is an example of
biomass?
A. open system
B. solar energy
C. nonrenewable energy resource
D. renewable energy resource