Download Chapter 12: Energy and Energy Resources

Chapter 12: Energy and Energy
Resources
Carin Miranda
6-1
2007
What is Energy?
• Energy is the ability to
do work.
• Work and energy are
both expressed in
joules (J).
Kinetic Energy
• Kinetic energy is the energy of motion.
• All moving objects have kinetic energy.
• Kinetic energy= mass times speed
squared divided by 2.
• The faster something is moving, the
more kinetic energy it has.
• The more massive the object the more
kinetic energy it has.
Potential Energy
• Potential energy is energy based on
shape or position.
• Gravitational potential energy is based
on height and weight.
• The higher an object the more potential
energy.
• The more massive an object the greater
the potential energy.
Mechanical Energy
• Mechanical energy is the total
energy of motion and position.
• In other words it is kinetic plus
potential.
• As potential goes up kinetic
goes down and vice versa.
Forms of energy
•
•
•
•
•
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Thermal (Heat)
Chemical
Electrical
Sound
Light
Nuclear
Thermal
• Higher temperature objects have more
thermal energy and more kinetic energy.
• The particles in steam move faster than
the particles in ice.
• The more particles the more thermal
energy.
• A bathtub full of 75 degree water would
have more thermal energy than a cup
full of 75 degree water.
Chemical Energy
• When particles are broken
down and cannot return to
their original form they have
chemical energy.
• Examples: Food, Charcoal,
gasoline, firewood.
Electrical Energy
• Moving electrons.
• Any electrical appliances or
anything using electricity.
• Huge magnets are rotated to
produce the electricity you
use at home.
Sound Energy
• Caused by an objects
vibrations.
• It is a form of potential
and kinetic energy.
Light Energy
• Vibrations of electrically
charged particles.
• Not all light energy is
seen.
• Microwaves use light
energy.
Nuclear Energy
• Two or more nuclei join together
(nuclear fusion). Example: Sun
• Nucleus of an atom splits apart
(nuclear fission). Example:
Uranium atoms split apart to
produce electricity.
Energy Conversions
•Any change from one
form of energy to
another.
Kinetic to Potential
• Remember we said as
potential energy goes up
kinetic goes down and vice
versa.
• Examples: Person on a
trampoline, pendulum, and
wind up toys.
Chemical Energy Conversions
• Chemical energy in food is converted into
kinetic energy when you move.
• It is stored as potential energy when you
aren’t moving.
• Where did that chemical energy come from in
food?
• The sun gives plants light energy and they
convert it into chemical energy.
• Batteries are another example of chemical
energy.
Electrical Energy Conversions
• Lots of examples:
• Alarm clock: electrical to light and
sound.
• Battery: chemical to electrical
• Light bulb: electrical to light, thermal,
and sometimes sound.
• Blender: electrical to kinetic and
sound
Energy and Machines
• Machines make work
easier by changing the
size and/or direction of
the force required to do
the work.
Why Conversions are Important
•Make energy
useful.
•Make conversions
more efficient.
Conservation of Energy
• Friction is a force that opposes motion
between two surfaces that are touching.
• When energy is used to overcome
friction some energy is converted into
thermal energy.
• On a roller coaster potential energy is
greatest at the top of the biggest hill and
kinetic energy is greatest at the bottom
of the biggest hill.
Law of Conservation of Energy
• Energy can be neither created nor
destroyed.
• It can change from one form to
another.
• Every time an energy conversion
takes place some energy is always
converted into thermal energy.
Energy Resources
• A natural resource that can
be converted by humans into
another form of energy to do
useful work.
• Can be nonrenewable or
renewable.
Nonrenewable
• Cannot be replaced easily.
• Fossil Fuels: Formed from the
buried remains of plants and
animals that lived millions of years
ago.
• Coal, petroleum, and natural gas.
• Electrical energy from fossil fuels.
• Nuclear Energy (Uranium pellets).
Renewable
• Can be replaced over a relatively short
period of time.
• Solar Energy (SUN).
• Energy from water (Hydroelectric).
• Wind Energy.
• Geothermal (Hot water in the ground).
• Biomass (garbage).
Advantages and Disadvantages of
Nuclear Energy
• Advantages: very
concentrated form of energy
and nuclear power plants
don’t produce smog (CO2).
• Disadvantages: Produces
radioactive waste and it is
nonrenewable.