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?
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.
The law of
conservation of
energy indicates that
the amount of 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.
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.
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.
Law of Conservation of Energy (cont.)
•  Because energy transformations are
inefficient, some of the chemical energy
transforms to thermal energy and sound
energy that are released to the
environment.
•  An open system is a system that
exchanges matter or energy with the
environment.
Law of Conservation of Energy (cont.)
•  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.
Energy Transformations and
Electric Energy
•  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.
Energy Transformations and
Electric Energy (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.
Energy Transformations and
Electric Energy (cont.)
•  Geothermal plants transfer thermal
energy from the Earth to water, creating
steam that turns turbines in electric
generators.
•  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.
Energy Transformations and
Electric Energy (cont.)
•  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.
•  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.