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Energy and Energy Sources
IPC
I. The Nature of Energy
A. Energy is the ability to cause change.
1. Kinetic energy – energy in the form of motion.
a. The amount of kinetic energy an object has
depends on its mass and its velocity.
b. Kinetic Energy = mv2
2
c. Joules- the SI unit to measure energy.
2. Potential Energy - energy stored in a
motionless object, giving it the potential to
cause change.
I. The Nature of Energy
A. Energy is the ability to cause
change.
3. Elastic potential energy - energy
stored by things that stretch or
compress.
4. Chemical potential energy – energy
stored in chemical bonds between
atoms
I. The Nature of Energy
A. Energy is the ability to cause
change.
5. Gravitational potential energy – energy
stored by things that are above the Earth.
a. the amount of GPE and object has
depends on its mass, the acceleration due
to gravity, and its height above ground.
b. GPE= mass(kg) x 9.8 m/s2 x height(m)
II. Conservation of Energy
A. Energy Conversions – energy
changing from one form to another.
1. Fuel store energy in the form of
chemical potential energy.
2. Mechanical energy – the total amount
of potential and kinetic energy in a
system.
II. Conservation of Energy
B. Law of Conservation of Energy – Energy
may change from one form to another, but
the total amount of energy never changes.
1. Example – as a swing moves back and forth,
its energy continually converts from kinetic to
potential and back.
2. If the energy of the swing decreases, then
the energy of some other object must increase
by an equal amount.
3. Friction converts on the mechanical energy
into thermal energy.
II. Conservation of Energy
C. Converting mass to energy – you
must think of mass as energy when
discussing nuclear reactions. The
total amount of mass and energy is
conserved.
1. Nuclear fusion – two nuclei are fused
together – takes place in the sun.
2. Nuclear fission – two nuclei are broken
apart.
II. Conservation of Energy
D. Conservation of Energy in your
body.
1. Chemical potential energy from food
that is stored in your body is used to
fuel the processes that keep you alive.
2. The food calorie is used to measure
how much energy you get from various
foods.
3. One calorie is equal to 4,180 J.
III. Energy Sources – Fossil Fuels
A. Energy can not be created nor
destroyed according to the law of
conservation of energy, but energy can be
converted from one form to another.
B. Fossil fuels – formed from decaying
remains of ancient plants and animals.
1. Burning fossil fuels converts energy from
chemical bonds to light and heat.
2. Chemical energy in fossil fuels is more
concentrated than in other fuels such as wood.
III. Energy Sources – Fossil Fuels
C. Petroleum- thick, greenish-brown,
highly flammable liquid formed by
decayed ancient organisms
1. A process called fractional distillation
separates the compounds in petroleum.
2. Petroleum is used for plastics,
synthetic fabrics, and other products in
addition to its use as a fuel.
III. Energy Sources – Fossil Fuels
D. Natural gas is also a product of
ancient organisms.
1. It contains more energy per kilogram
than petroleum or coal.
2. It burns more cleanly than other fossil
fuels.
3. It provides about one-fourth of the
energy consumed in the United States.
III. Energy Sources – Fossil Fuels
E. Coal – a solid fossil fuel found
underground.
1. It produces more pollution when
burned than natural gas or petroleum.
2. It provides about one-fourth of the
energy produced in the United States.
3. About 90 percent of coal burned in the
United States is used to produce
electricity.
III. Energy Sources – Fossil Fuels
F. Electricity is generated when fossil fuels
are burned.
1. The burned fuel releases thermal energy.
2. The thermal energy produces high pressure
steam.
3. The steam spins a turbine.
4. The spinning turbine produces an electric
current.
5. The electric current is transmitted through
power lines to consumers.
III. Energy Sources – Fossil Fuels
G. Only about 35% of the energy in
fossil fuel reaches consumers since
some energy is lost in every stage of
the process.
III. Energy Sources – Fossil Fuels
H. Fossil fuel have some undesirable
side effects.
1. Fossil fuel pollute the environment and
increase carbon monoxide in the
atmosphere.
2. Mining coal can cause health problems
for miners.
III. Energy Sources – Fossil Fuels
I. Fossil fuels are nonrenewable
resources, so it is important to not
waste energy.
IV. Nuclear Energy
A. About 20% of the electricity in the U.S.
come from nuclear power plants.
B. Nuclear reactors contain a fuel, rods to
control nuclear reactions, and a cooling
system.
1. Heat is produced by nuclear fission – energy
is released when U-235 nuclei split in two after
being struck by a neutron.
2. Special rods absorb excess neutrons to
prevent dangerous chain reactions
IV. Nuclear Energy
C. Nuclear Power plants use the heat
of nuclear fission to produce steam.
1. The steam drives a turbine.
2. The Turbine rotates an electric
generator.
IV. Nuclear Energy
D. Nuclear power plants produce
nuclear waste—radioactive byproducts from radioactive materials.
1. Low-level wastes contain only a small
amount of radioactive material.
2.High-level wastes must be disposed of
extremely carefully because they will
remain radioactive for tens of thousands
of years.
IV. Nuclear Energy
E. Nuclear Fusion—the joining
together of nuclei—is not a practical
energy source due to the high
temperature fusion requires.
V. Renewable Energy Sources
A. A renewable resource can be
replaced as quickly as it is used.
V. Renewable Energy Sources
B. Solar energy is converted into
electricity by a photovoltaic cell or solar
cell.
1. A solar cell converts only 15 to 20 percent
of the sun’s energy into electricity.
2. Energy produced by solar cells is more
expensive than energy produced with fossil
fuels.
3. Energy from solar cells must be stored in
batteries when the Sun is not shining.
V. Renewable Energy Sources
C. Hydroelectricity is produced by
moving water; it is about twice as
efficient as fossil fuels or nuclear
power.
V. Renewable Energy Sources
D. Tidal energy uses moving water,
but it can only be used in places
where high and low tides are
different enough.
V. Renewable Energy Sources
E. Windmills can be used to generate
electricity, but are useful only when
the wind blows consistently.
V. Renewable Energy Sources
F. Geothermal energy—thermal
energy contained in hot magma;
limited to areas where magma is
close to the surface.
V. Renewable Energy Sources
G. Alternative fuels include hydrogen
gas and biomass—renewable organic
matter such as wood or animal
manure.