2. FORMS AND SOURCES OF ENERGY
ENERGY produces changes in our bodies. There are many forms of energy :
5. Kinetic energy
Thisistheenergyinmoving
bodies,likerocksshooting
out of avolcano.
1. Thermal /Heat
energy
This is the energy
transferred byhotbodies,
likelava, to colder bodies.
2. Light energy
This is the energy of
bodiesthatemitlight,as
a fire.
3. Chemical energy
This is the energy stored in
some materials, like
batteries and fuel and in
living things and foods.
4. Electrical energy
This is the energy in a
lightning bolt and the
energy electrical devices
use.
6. Sound energy
This is a type of kinetic
energy. It is produced by
the vibration of bodies or
the air.
3. SOURCES OF ENERGY
WIND and PETROL supply energy and are known as ENERGY SOURCES. There are two types:
THESUN, WINDAND WATERsupply renewable
energy because they are constantly being
renewed.
We may run out with FOSSIL FUELS because we are
using them fasterthan we can produce them.
Renewable energy sources
Wind turbines
transform wind
energy into
electricity.
Hydroelectric
power stations
transform falling
water into
electricity
Solar panels transform
solar energy intoheat
or electricity
Moving
water
The Sun´s
rays
Wind
It is minedfromthe
ground.
We burn it to
produce heat and
electrical energy.
Gas
PetrolCoal
It is extracted by
drilling into the
ground.
We useitprimarilyfor
heating.
It is extracted by
digging wells in the
ground.
We use it to produce
fuel and plastics.
Non-Renewable energy sources
4. All bodies have a temperature.
When we say that something is
hot or cold, we want to say that
its temperature is high or low.
Thispropertyismeasured witha
THERMOMETER.
When we reach the same
temperature, wesay that they
are theTHERMAL EQUILIBRIUM.
HEAT
When a body receives energy
in the form of heat, three
phenomena can occur:
EXPANSION
When a body
gets hotter,its
volume
increases.
CONTRACTION
When a body
getscolder,its
volume
decreases.
When hot bodies get colder
or when cold bodies get
hotter.
For example:
When hot chocolate and
cold milk are mixed, the
temperature of each one
change.
Change of state
Change of volume
Change of
temperature
Temperature and heat
How heat affects bodies
-
-
-
Condensation: The
change from gas to
liquid.
Solidification: The
change from liquid to
solid.
Evaporation: The
change from liquid to
gas.
- Fusion: Thechange
fromsolidtoliquid.
5. LIGHT
MIRRORS ARAINBOW
They are opaquebodies The light pass
with a polished Surface through drops
that reflectlight. of water.
They can be: flat,
concave or convex
mirror.
Propagation of light Properties oflight
Light us a form of energy that
illuminates the world.
They can be classified into two
groups:
- Transparent: They
allow lightto pass
through, like
glass.
- Opaque: They prevent
light from passing
through, likeabook.
- Translucent: Theyallow
light to pass through,
but it is diverted, like
some plastics.
- It travels athigh
speed.
- It moves in a
straight line.
- It propagatesin
all directions.
Natural light
sources
They arefound
is nature. They
emittheir own
light.
For example:
The Sun,stars,
flashes or
fireflies.
Artificial light
sources
They are
man- made.
They
transform
energy into
light.
This is the
change of
directionthat
occurs when
light passes
from one
medium to
another.
This is the change of
direction thatoccurs
whenlighthitsan
object.
We can see objects
that don´t emit
their own light.
RefractionReflection
We can classify
bodies based on
how they respond to
light.
It moves fromone place
to another until itcomes
into contact with a
body.
Bodies and lightSources of light
6. SOUND
It isaformofenergy.Itisproducedbythevibration
of bodies. We perceive it through our sense of
hearing.
Volume TimbrePitch
Noise pollutionPropagation of sound
Qualities of sound
- Ittravelsmuch
more slowly than
light.
- It moves inastraight
line.
- It propagates in all
directions.
We can reduce noise pollution if
we limittheamountofvehicle
traffic, listen to music at an
appropriate volumeand avoid
shouting and unnecessary noise.
It propagates through a
NATURAL MEDIUM , as air
or the ground.
Noise pollution is the excessive
noisethatmayharmour health.
They can cause anxiety, bad
temper and insomnia.
This makes is
possible to
differentiate
between sounds
with the same
pitch and
volume, based
on the bodythat
emits them.
Thismakes it
possible to
differentiate
between:
- LOUD SOUND,
like an
engine.
- QUIET SOUND,
like the
tweeting of a
bird.
It can be:
- HIGH, likethe
sound of
violin.
- LOW, like the
sound of a
doublebass.
Noises are unpleasant sounds to
the ear because they are very
loud or veryhigh.
7. Static electricity
It is the type of
electricity which
causes certain
bodies to be
attracted orrepelled.
ELECTRICITY
Electrical charge
Electric current and electric circuits
Normally, bodies are
neutral but when we
rub them, we are
adding morepositive
charge or more
negative charge.
ELECTRICAL CONDUCTOR
They allowthe electricitytoflow
through them.
When two bodies
with differentcharge
are close,theyattract
each other.
When two bodies
have the same
charge, they repel
each other. RESISTOR
It converts electricity into
another type of energy.
SWITCH
It opens or closes the circuit.
POWERSOURCE
A power source, as
a battery,provides
the energy.
When an electric charge
moves, itformsanelectric
current.
Itisa property of matter that
causes forces of attraction or
repulsion between bodies.
In orderforthecurrentto flow, it
requiresan electric circuit made
up of different components:
8. THE EFFECTS OF ELECTRICITY
In aradio,electricalenergy
is transformed into sound
energy.
In alamp, electrical energy
is transformed into light
energy.
In a mixer, electrical
energy is transformed into
kinetic energy.
In a toaster, electrical
energy is transformed into
heat energy.