Forms and uses of
energy
Questions to think about…
What are the
uses of energy?
What are the
forms of energy?
Can one form of
energy change into
another form?
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All living things need energy to
Do non living
survive. Plants get their energy
things also need
from the Sun to make food and
energy? Where
grow, while animals and people
does the energy
get their energy from the food
come from?
they eat.
Forms of energy and their uses
• There are different forms of energy:
Forms of energy
kinetic energy
light energy
electrical energy
heat energy
sound energy
potential
energy
gravitational
potential
energy
chemical
potential
energy
elastic
potential
energy
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Kinetic energy
• A moving object has
kinetic energy.
• For example, when you
swing your arm, your arm
has kinetic energy.
• When you throw a ball,
the moving ball has
kinetic energy.
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Kinetic Energy
The speed of
the object
affects the
amount of
kinetic
energy.
The faster
the object,
the more
kinetic
energy.
Kinetic energy
• The amount of kinetic energy an object has depends on the
speed of the object.
• The faster the object moves, the more kinetic energy it has.
• For example:
– the faster you stir a drink, the more kinetic energy the drink has.
– the faster the water in a river flows, the more kinetic energy the river
has.
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Kinetic Energy
The mass of
the object
affects the
amount of
kinetic
energy.
The heavier
the object,
the more
kinetic
energy.
The dog is moving
faster so it has more
kinetic energy.
Kinetic energy
• Its uses:
Wind turbines
use energy
kinetic from the wind and
–o People
use kinetic
energyfor
from
the wind to
waves
recreational
activities.
generate electricity.
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Where does the energy
she uses to jump come
from?
It comes from the
food she eats.
• Green plants trap light energy from the sun to carry
out photosynthesis to make food. This is stored as
chemical potential energy.
Food stores
chemical
potential
(stored) energy.
• This energy is transferred to living things that eat
these plants.
• The chemical potential energy helps us carry out
different life processes.
Chemical Potential Energy
– Food
• Food stores chemical
energy.
• The food that we eat
gives us energy to do
work and keep our
bodies warm.
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Batteries
• Non-living things need to get their energy from a
source in order to move.
• For example, a robot can get its energy from
batteries. Batteries store chemical potential energy.
• The chemical potential energy is converted to
electrical energy when the robot is switched on.
Fuels
• Fuels can burn to give off heat and light energy.
• Fuels store chemical potential energy.
• Other examples of fuels are: oil, gas, wood, candle,
charcoal and coal.
Potential energy
Food, batteries and
fuels store energy.
This stored energy is
known as chemical
potential energy.
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Elastic Potential Energy
• Objects such as springs
and rubber bands can also
store energy.
• The more you stretch a
rubber band, the more
elastic potential energy it
has.
Springs
Does an unstretched spring
possess elastic potential
energy? No.
Does
Doesaan
compressed
stretched spring
spring
possess elastic potential
energy?
Yes.
Yes.The
Themore
morecompressed,
stretched, the
the
more elastic potential energy.
Gravitational Potential Energy
• Gravitational
potential energy
– When an object is
above the ground, on
top of a slope or
hanging from
something, it stores
energy.
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Gravitational Potential Energy
The height of
the object
affects the
amount of
gravitational
potential
energy.
The higher
the object,
the more
gravitational
potential
energy.
Gravitational Potential Energy
IfFor
theexample,
egg falls aover
the edge,
stationary
egg
the
potential
on top
of theenergy
edge ofisachanged
kitchen
to
kineticdoes
energy.
cabinet
not have kinetic
energy. It has gravitational
potential energy because of its
position on top of the edge of
the kitchen cabinet.
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Gravitational Potential Energy
– A pile driver is used to drive
heavy piles into the ground.
– The hammer has
gravitational potential
energy when it is lifted high
above the ground.
– The gravitational potential
energy is changed to kinetic
energy as the hammer falls
down towards the pile on
the ground.
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Question
More
gravitational
potential
energy = More
kinetic
energy???
Gravitational Potential Energy
• Some things in the
environment, such as a
waterfall, have
gravitational potential
energy due to their
position above the ground.
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Forms of energy and their uses
• There are different forms of energy:
Forms of energy
kinetic energy
light energy
electrical energy
heat energy
sound energy
potential
energy
gravitational
potential
energy
chemical
potential
energy
elastic
potential
energy
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Activity 2.1 & 2.2
Potential energy
• Gravitational potential energy
– Can you identify in the photos below, the things that have
gravitational potential energy?
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Activity 2.3 & 2.4
Light energy
• Light energy is a form of energy that allows us
to see.
• The Sun is the primary source of light energy
on Earth.
• Lamps, candles and torches are also sources of
light energy.
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Light energy
• Light energy is also used to communicate or send
messages.
• For example:
– Traffic lights help to control the flow of traffic at road
junctions.
– Signal lights of a vehicle let us know the direction that
the vehicle is heading.
signal light
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Electrical energy
• Electricity is a form of energy which is also
known as electrical energy.
• We use electricity in our homes, schools,
offices, and almost everywhere else.
• Some electrical equipment, like torches and
clocks, use energy from batteries.
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Electrical energy
• Solar-powered equipment, such as some watches
and calculators, use electrical energy from solar cells.
• Solar cells capture energy from the Sun and convert
it to electrical energy.
solar cells
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Electrical energy
Chemical
potential
energy
Electrical Energy
Light and heat energy
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Electrical energy
Chemical
potential
energy
Electrical Energy
Sound energy
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Heat energy
• Heat energy is a form of energy that we can feel.
Heat energy makes us feel warm or hot.
• The Sun
– The Sun is our main source of heat energy.
– Heat energy from the Sun can dry many things such
clothes, shoes and mattresses.
– Heat energy is produced whenever things are rubbed
together or when they are hit against each other.
Sound energy
• Sound is a form of energy that
we can hear.
• Sounds are all around us.
• They can be very noisy, like
thunder, or soft, like a whisper.
• We use sounds to
communicate.
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Energy conversions
• Energy changes from one form to another.
– For example, during photosynthesis, plants use energy from
sunlight to make food.
– Light energy from the Sun is changed to chemical energy in the
plants.
Sun
plant
light energy
chemical energy
food
Energy conversions
chemical potential energy
kinetic energy
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Energy conversions
electrical energy
light energy + sound energy + heat energy
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Energy conversions
• Energy changes from one
form to another.
– Light energy from the Sun can
be used to generate electricity.
– Solar cells in a solar-powered
vehicle can change light energy
from the Sun to electrical
energy to move the vehicle.
light energy
electrical energy
solar-powered car
kinetic energy
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Energy conversions
gravitational potential energy
kinetic energy
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Activity 2.5 and 2.7