2. Mechanical and chemical energy
Mechanical energy is a form of energy an object has due to its motion and
position. It’s the sum of potential energy from the position and of kinetic
energy from the motion.
Potential energy is the stored energy
of an object because of its position.
Kinetic energy is the energy of an
object because of its motion.
3. Mechanical and chemical energy
Chemical energy is energy stored in all matter. It’s released through a
chemical reaction. Chemical energy is a type of potential energy because it’s
an energy that is stored.
4. Light energy
Light is the form of energy that allows us to
see things because it travels in waves, bounces
off objects and then enters your eyes.
There are natural light sources and artificial
light sources.
Stars, candles, fire are natural light sources.
They change chemical energy into light energy.
Light bulbs, television screens and a torch are
artificial light sources. They change electrical
energy into light energy.
5. Light energy
Light travels through some objects. It depends on the material the
object is made of.
Opaque objects
Light can’t travel
through them.
Transparent objects
Light can travel
through them.
Translucent objects
Only some light can
travel through them.
6. Light energy
There are three ways in which light travels through objects.
Reflection
It is when light
bounces off a surface.
Refraction
It is when light travels
at different speeds
and changes direction.
Dispersion
It is when white light
travels through a
prism and it separates
into different colours.
7. Sound energy
Sound is the form of energy that allows us to hear things because it travels
in waves and makes the air vibrate. This vibrations enter our ears.
Sound can travel
through solids.
It can also travel
through liquids...
… and through gas.
But sound can’t travel through a completely empty space, called vacuum.
9. Sound energy
Sound has three properties:
Pitch
It is how high or
low the sound is.
Intensity
The loudness is related
to the intensity of the
sound.
Timbre
It is the tone or
quality of the sound.
10. Thermal and electrical energy
Thermal energy is the kinetic energy
caused by the movement of particles in
matter. When the particles move quickly,
thermal energy is high. When the particles
move slowly, thermal energy is low.
Temperature is related to the movement of particles and measures the
thermal energy of a substance.
Changing the thermal energy of substances can make them change state.
When the temperature increases in an object, its volume increases and it
expands. This is called thermak expansion.
11. Thermal and electrical energy
How is thermal energy transferred?
Conduction
It is a direct
transfer of thermal
energy through
contact.
Convection
It is the transfer
of thermal energy
by the movement of
fluids.
Radiation
It is the transfer
of thermal energy
from the Sun
through waves.
12. Thermal and electrical energy
Electrical energy happens when there is a flow or current of electric
charge. It’s a form of energy which we use to power machines.
One end of the battery has a positive charge and the other end has a negative
charge. Electric charge flows when we put the battery into a machine.
This energy makes the machine
work. The electric current is
conducted along a path used to do
work in an electric circuit.
13. Energy sources and saving
energy
There are two types of energy sources:
> Renewable energy sources > Non-renewable energy sources
14. Energy sources and saving
energy
There are two types of energy sources:
> Renewable energy sources: are resources that are replaced naturally over
time.
wind energy bioenergy solar energy hydroelectric
15. Energy sources and saving
energy
There are two types of energy sources:
> Non-renewable energy sources: are resources that are available in limited
quantity.
nuclear coal natural gas petroleum
16. Energy sources and saving
energy
Non-renewable resources cause pollution.
We have to burn coal, gas and petroleum to
release energy. This process releases gases
that are harmful to the environment and
pollute the atmosphere.
One of the biggest problems is the global
warming.
Our planet is getting warmer. This has very
bad consequences for life on Earth: the
melting of glaciers and the rise in sea levels.
17. Energy sources and saving
energy
What can we do to save the planet?
walk or cycle
use public transport
insulate your home
use energy-efficient
machines
use solar panels
use a pellet stove
drive a hybrid or
electric car
use wind turbines
to power your home
