Energy in action
Energy shapes Earth and the universe. The transfer of energy from
place to place and the transformation of energy from one form
into another makes things happen. In this way, energy does work.
If there was no energy, nothing would ever happen and nothing
would ever change.
Earth and space use energy
Everything that happens on Earth or in outer space involves energy.
There are many different forms of energy. Earth’s movement, the
Sun’s warmth, the weather we experience and a space rocket’s
movement all involve energy.
In this book …
Energy is essential to life
We see energy in action every day. Energy is used by all living things.
We use energy to cook our food, keep warm, move about and
provide power to our homes. Without energy, life would not exist.
There are exciting
real-life examples
showing how
different forms
of energy work
on Earth and in
space.
Everything
that happens on
Earth and in outer
space involves many
different forms of energy.
See pages 10–11 to find
out more about these
forms of energy.
The Sun provides light
energy and heat energy.
Rocket fuel contains
chemical energy.
We cannot see energy
but it is all around us
and is used by everything
in the universe. Energy keeps
living things alive, makes all our
technology work, provides power
to our vehicles and causes all
our weather.
The spinning Earth
has kinetic energy.
Lightning strikes are made by
electrical energy, and produce
light and sound energies.
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5
What are energy, matter
and forces?
Forces are actions
A force is an action, such as a push, pull or twist, which is applied
to an object. Forces act in pairs. They can act between two objects
that are touching, such as a ship hitting an iceberg, or even when
objects are apart, such as Earth and the Moon.
Energy makes everything happen but it does not work alone.
Energy works with matter and forces. To understand how energy
works, we must understand what energy, matter and forces are.
If this ship hits the
iceberg, the pushing
force of the ship would
be applied to the
iceberg, which would
cause the iceberg to
break up. The iceberg
would also apply a
pushing force to the
ship, which could
damage the ship.
Energy does work
Energy is not a substance like air or water. It is the ability to do
‘work’. For example, heat energy works to boil water, electrical
energy works to run a motor and light energy works to help
plants grow.
Energy cannot be created
or destroyed. Instead, it is
changed (transformed) from
one form into another or
moved (transferred) from
one place to another.
Matter is everything around us
Everything in the universe is made of matter, including all living
and non-living things. Matter is made of tiny particles called
atoms. Inside an atom are electrons and a nucleus. Matter can
be either a solid, a liquid or a gas. This usually depends on how
close together its particles are, as well as the mass of the particles
and how much energy they have.
The nucleus has a
positive electrical
charge.
Electrons have a negative
electrical charge. They spin
around the nucleus.
The particles of liquid matter,
such as water, are held quite
close together by weak forces.
These weak forces give liquid
matter an indefinite shape.
Forces act
between different
objects, or matter, and
also inside all objects. Forces
act inside matter to hold the
particles of matter together.
The strength of these
forces affects the shape
of matter.
6
nucleus
electron
You can observe how matter can be
a solid, a liquid or a gas by heating
some ice in a saucepan on the
stove. The ice is solid water. As it
melts it becomes liquid water, then
as it heats further it becomes a gas
called water vapour.
The particles of gaseous matter,
such as air, are very far apart
because they are held together
by very weak forces. These very
weak forces give gaseous matter
an indefinite shape.
atom
All the matter in
the universe, including
the matter that makes up
Earth, is made of tiny
atoms.
Try this
The particles of solid
matter, such as plants
and soil, are held tightly
together by strong
forces. These strong
forces give solid matter
a definite shape.
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How do energy, matter
and forces interact?
Energy cannot do work by itself. For work to be done, forces must
act on matter. Forces are constantly transforming the energy of
matter from one form into another and transferring energy from
one place to another.
The force of
friction transforms
and transfers energy
to make a volcano
erupt.
Forces transfer and transform energy
Forces transfer energy to matter to make matter move, change
its motion or transform the type of energy matter has. Forces can
change the shape of matter or make it heat up.
Forces acting on Earth and in outer space
Forces that transfer and transform energy on Earth and in outer
space include gravity, magnetism and friction. Air resistance
is a force that happens only in Earth’s atmosphere
because there is no air in outer space.
2. Melted, liquid
rock is pushed to the
surface of Earth and
escapes through a
volcano as lava.
• Gravity is a force of attraction
between two objects.
• Magnetism is a force of
attraction or repulsion that acts
on objects in a magnetic field.
• Friction is a force that makes it
difficult for one object to move
across the surface of another.
1. Earth’s crust is made
up of massive plates
that can move against
each other. The force
of friction from this
movement transforms
and transfers energy,
melting solid rock into
hot, liquid rock.
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• Air resistance happens when a
moving object pushes air out of
its way.
3. The force of gravity transfers energy
to the lava, making it flow down the
volcano’s sides to the ground below.
Forces make energy
move through matter
When forces act on matter, energy
is able to move through matter in
different ways. It can make particles in
matter bump together or it can move
as waves.
Waves of light or sound energies
move through matter in a similar
way to waves moving through
the ocean. Ocean waves transfer
their energy through the water
without moving the water. The
water stays in the same place,
only moving up and down as the
wave passes.
Some forms of energy
can move through matter
as waves
Some forms of energy, such as light
and sound energies, can move through
matter as waves.
As a wave of energy travels through
matter, it moves matter’s particles up,
down, forwards or backwards. This is
called vibration. Once the wave has
passed, the particles go back to their
original position.
You can think of a wave travelling
through matter like water waves rising
up and down on the open ocean.
As the wave moves along, the
body of water stays roughly in
the same place.
Try this
Sound is a wave that is caused
by something that is vibrating. Put
your fingers against your throat and
hum. Can you feel the vibrations
caused by air being pushed
across your vocal cords? When
you make a loud sound, you can
feel the vibrations get bigger. This
is because larger vibrations have
more energy than small vibrations.
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