Forms of Energy
Year 8 Science
Useful and Wasted Energy
Kinetic Energy :
Energy
Potential Energy
• A property of matter that allows
it to do ‘work’.
• Energy can either be:
• Kinetic energy
• Potential energy
• Law of Conservation of Energy:
• Energy cannot be created, nor
destroyed, only transformed into
other types.
• The energy of movement.
• There are many types of kinetic
energy:
• Mechanical kinetic energy
• Heat energy
• Light energy
• Sound energy
• Electrical energy
• Energy that is stored.
• Stored energy gives an object
the potential to do work.
• There are many types of
potential energy:
• Gravitational potential energy
• Chemical potential energy
• Elastic potential energy
• Nuclear potential energy
Energy Transfer
• During an energy transformation, energy can be converted into useful and wasteful energy.
• Scientists and engineers try to ensure that almost all energy is converted into useful forms of energy.
• The flow of energy from one
object to another.
• During an energy transfer, the
energy does not change form.
• Kinetic energy of a boot passing
into a football.
• Heat energy in a metal bar moving
from one end to another.
• Light energy from the Sun
traveling towards the Earth.
Energy Transformation
• The conversion of one type of
energy to another.
• We represent energy
transformations using an energy
flow diagram.
• The arrow always points from the
original form of energy, to the final
form of energy.
Law of Conservation of Energy
• Energy can not be created nor
destroyed. It can only be
transferred or transformed from
one type to another.
• Energy might be passed on or
wasted, but it is never lost.
• If one object wastes energy, then
it is always gained as another
object, usually as heat.
By Jaxon Stone 8.6
Heat Transfer
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Heat transfer is a form of energy
transfer.
• When heat moves from one place to
another.
• When an object increases in
temperature, the particles in that
object begin to speed up.
• Heat transfers in three
mechanisms:
• Conduction
• Convection
• Radiation
Conduction
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The transfer of heat energy
through a solid object.
• The kinetic energy passes through
the object as the particles collide
with each other.
• Each particles speeds up a
neighbouring particle, transferring
heat.
Convection
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The transfer of heat through
liquids and gases.
• These substances are called fluids.
• When fluids increase in
temperature, they expand.
• The fluid is now less dense.
• The more dense, colder fluid falls
and the less dense, warmer fluid
rises.
• This transfers heat throughout the
fluid
Radiation
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The transfer of heat through
electromagnetic waves.
• Radiation does not need a
medium to travel through.
• It can travel through the vacuum
of space.
• Radiation often travels in the
form of light
Energy Efficiency:
A measure of how much input
energy is transformed into
useful energy.
• When most of the input energy
gets converted into useful energy,
the device is energy efficient.
• When most of the input energy
gets converted into wasteful
energy, the device is energy
inefficient.
Why is Energy Efficiency Important?
• By purchasing appliances that
are more efficient, your
household will save energy and
save on energy costs.
• Most large electrical appliances
carry a red and yellow energy
rating label.
• The more stars, the more energy
efficient.
Kinetic Energy: Mechanical Kinetic Energy
• Sometimes called ‘kinetic
energy’.
• The faster an object moves, the
more mechanical kinetic energy
it has.
• The heavier an object the more
mechanical kinetic energy it has.
Kinetic Energy: Heat Energy
• Kinetic energy due to the movement of particles.
• When an object increases in temperature, the particles begin to collide at greater speed.
• Heat energy moves from hot objects to cold objects.
Kinetic Energy: Light Energy
• Energy due to the movement of electromagnetic waves.
• Light does not need a medium to travel through.
• This means light can travel through space.
• The energy of light is described by the electromagnetic spectrum.
• The higher the frequency of light, the higher the energy.
Kinetic Energy: Sound Energy
• Energy due to particles vibrating.
• Our ears detect sound energy and convert it into an electrical signal our
brain can interpret.
• The louder the sound, the more energy.
Kinetic Energy: Electrical Energy
• Energy that is possessed by
electrons moving in a wire.
• Electrons are a particle found in
the atom.
• Electrical energy is converted to
many different forms to perform
work. This can include:
• Charging your phone
• Powering a TV
• Toasting bread
Potential Energy: Gravitational Potential Energy
• The energy an object stores because it is above the ground.
• The greater the height of the object, the more gravitational potential
energy.
• The higher the altitude, the higher the gravitational potential energy.
• Gravitational potential energy is transformed into kinetic energy when an
object falls.
Potential Energy: Chemical Potential Energy
• Energy stored in substances.
• Can be released in a chemical
reaction.
• Burning fuel
• Respiration
• Chemical potential energy is
stored in sugar during
photosynthesis.
• The chemicals in a battery store
chemical potential energy.
Potential Energy: Elastic Potential Energy
• Energy stored in an object that
has changed shape.
• An elastic band being stretched.
• A spring being compressed.
• If the object is released after it is
deformed, the elastic potential
energy can be transformed into
kinetic energy.
Potential Energy: Nuclear Potential Energy
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Energy stored in atoms.
• This energy is used to keep the
atom together.
• Nuclear energy is transformed
into heat and light energy:
• when a nuclear bomb explodes
• in a nuclear power plant
• inside the Sun
The Joule
• Energy is measured using a unit
called the Joule (J).
• You use one Joule of energy when
you lift a 1 kilogram mass 10 cm
off the floor.
• A Joule is so small, that we
usually measure energy in
kilojoules or megajoules.
1 𝑘𝐽 = 1 000 𝐽
1 𝑀𝐽 = 1 000 000 �