Quarter 3 in science 7 ENERGY

1. - The capacity of an object or a
system to do work and carry out
vigorous activity.
Lesson
3:

2. Table of contents
01
LIGHT
HEAT
03
ELECTRICITY
04
02
SOUND

3. Sound
Energy

4. A. Production of Sound
► SOUND is produced because the particles of the medium vibrate.
The vibration of the particles enables the materials or the objects
produced sound. Any object or materials are medium that transmit
the sound.
► Sound travels in the form of a wave. Since it cannot travel without
medium, SOUND is considered as MECHANICAL WAVE.
► Vibrations of a sound allow the particles of its medium to compress
at one point and spread apart at another point. This succession of
compressions and rarefactions makes sound a longitudinal wave.

5. SOUND WAVES

6. A. Production of Sound
► You produced sound when you talk, laugh,
shout, scream, sing, hum and make other
utterances. You can do all these because of
your LARYNX. Inside your larynx are two tissue
bands that make up your VOCAL CHORDS.
► Larynx is also known as the HUMAN VOICE BOX.

7. The Human Voice Box

8. B. Transmission of Sound
► SOLIDS have compact particles making them
good transmitters of sound. On the other hand
GASES like air have loose particles, making
vibrations travel through them more slowly.
► Sound can travel through liquids. Liquids
transmit sound better than gases do much less
than solids.
► Sound CANNOT be transmitted in a vacuum
because there are NO PARTICLES in VACUUM

9. C. Reception of Sound
► What enables you to hear a SOUND ?
► Sound perception or what is commonly called
HEARING is one of your 5 senses. It is made
possible by your EARS.

10. C. Reception of Sound
► To receive sound, there must be a source, a
medium to transmit and a receiver.
► The human ear can perceive sound with
frequencies range from 20 hz to 20,000 hz.
► Sounds having frequencies above 20,000 hz are
called ULTRASOUND while those with
frequencies below 20 hz are called
INFRASOUND.

11. D. Characteristics of a Sound
► A sound can be described in terms of its
loudness, pitch and quality.
1. Loudness
► Sound can be either SOFT and LOUD.
► The LOUDNESS of a sound depends on the sound’s
intensity or energy used to make vibrations in the
sound’s medium.
► Loudness is also affected by a listener’s capacity to
hear.

12. D. Characteristics of a Sound
► A sound can be described in terms of its
loudness, pitch and quality.
2. Pitch
► Pitch is a characteristics of a sound that refers to its
highness or lowness.
► It is determined by the frequency of the waves
producing the sound.

13. D. Characteristics of a Sound
► A sound can be described in terms of its
loudness, pitch and quality.
3. Quality
► The characteristics of a sound that gives it its
distinguishable feature is called QUALITY.
► This characteristics enables you to distinguish the
sound of a guitar from a drum.

14. E. Musical Sound and Noise
► Any pleasant sound perceived by a
receiver can be considered a form of
“music” or a MUSICAL SOUND.
► NOISE, on the other hand, is any
sound that is unpleasant to the
receiver.

15. LIGHT
Energy

16. - Light is what enables us to see
the things around you. SUN is
the major source of light on
earth.
- The absence of enough
sunlight for illumination, people
use artificial sources of light
such us lightbulbs, lamps,
candles and torches.

17. A. Theories about LIGHT
► ISAAC NEWTON, proposed the
corpuscular theory, which claims that
light is made up of tiny particles
called corpuscles released by a
source.
1. Corpuscular Theory

18. A. Theories about LIGHT
► CHRISTIAN HUYGENS, advocated the
wave theory, which proposed that
light was made of waves that peak
from surfaces like layers of an onion.
2. Wave Theory

19. A. Theories about LIGHT
► MAX PLANCK, studied the relation
between the energy and the
frequency of light.
► He proposed his theory in 1900,
that light is a wave that carry energy
in certain distinct amounts.

20. A. Theories about LIGHT
► In 1905, ALBERT EINSTEIN,
proposed that light is not a
wave, but it is made up of
localized particles and is
produced when electrons jump
from one energy level to
another.

21. A. Theories about LIGHT
► In 1922, LOUIS DE
BROGILE, proposed the dual
nature of light, that light
can be either a wave or a
particle but never both at
the same time.

22. B. Transmission of Light
► Light is a form of energy that travel
through space in the form of
electromagnetic wave.
► It does not require medium to
transmit.
► Rays of light travels as transverse
wave.

23. B. Transmission of Light
► When the light hits
TRANSPARENT material like
clear glass or plastic almost all of
it is transmitted through the
material.

24. B. Transmission of Light
► Light also travels through
TRANSLUCENT material like smoked
glass or colored plastic.
► Not all of it can be transmitted through
this material, barring you from clearly
seeing it through.

25. B. Transmission of Light
► When light is made to pass through an
OPAQUE material like a book or a block of
wood, none of it is transmitted.
► All the light is blocked and this result in the
formation of shadows.
► This makes it impossible to look through the
wooden walls.

26. C. Characteristics of Light
► Light can be described in terms of its
brightness. The brightness of a source of light is
expressed as luminous intensity or the amount
of radiant energy transmitted to a source. This
can be measured in terms of the unit CANDELA
(cd).
► The brighter the light source the greater the
amount of light energy it transmits.

27. C. Characteristics of Light
► The amount of Radiant Energy is visible
to the eye which is transmitted per unit of
time per unit area is known as LUMINOUS
FLUX. More luminous flux indicates that
the light source has greater intensity.

28. C. Characteristics of Light
► When the light hits an object, the
object’s surface is illuminated.
Illumination depends on luminous
intensity and distance between
source and the object.

29. C. Characteristics of Light
► Visible Light is the light that people can
see.
► It is composed of different colors, with
the color of light depending on its
frequency and wavelength.

30. C. Characteristics of Light
► These colors are arranged in
increasing frequency: RED,
ORANGE, YELLOW, GREEN,
BLUE, INDIGO, VIOLET.

31. Heat
Energy

32. HEAT and TEMPERATURE are closely
related concepts. While
TEMPERATURE describes how COLD
or HOT a body is, HEAT is defined
as the energy that is transferred
from one body to another due to
temperature differences
Common units of TEMPERATURE are °C or °F and standard unit
Kelvin (K). HEAT is expressed in terms of the unit calorie (cal.)

33. A. Heat Transfer
► The transfer of heat stops only when the
objects in contact already have the same
temperature or are said to be in THERMAL
EQUILIBRIUM.
► Heat can be transferred from a body to another
by three modes: Conduction, Convection and
Radiation.

34. A. Heat Transfer
► is described as the transfer of heat among
SOLIDS.
► Metals are the best conductors of heat because
they have many FREE ELECTRONS.
► Cloth, Wood and Plastic are examples of
INSULATORS, or poor conductors of heat.
1. CONDUCTION

35. A. Heat Transfer
► Another mode of heat transfer is convection,
which involves the movement of liquids and
gases.
► The Rising and Sinking of the molecules
form a circling motion known as CONVECTION
CURRENT.
2. CONVECTION

36. A. Heat Transfer
► The third mode of heat transfer is
radiation, which involves heat from one
body moving through space in the form of
waves and being absorbed by another
body.
3. RADIATION

37. ELECTRICAL
ENERGY

38. Electricity is the flow
of electrons moving in
atoms of matter. It is
the common term used
to refer to electrical
energy.

39. A. Pioneers of
Electricity
 About 600 BCE, Thales, a
Greek philosopher, first
observed the electrical nature of
matter. He observed that after
rubbing a piece of of amber rod
with wool the rod could pick up
small pieces of paper.

40. Pioneers of
Electricity
 The same thing was observed
by William Gilbert in 1600.
 He found out that many
materials exhibited the
« AMBER EFFECT ».
 To describe this effect he
used the term ELECTRICUS,
which derived from the Greek
word elektron, meaning

41. Pioneers of
Electricity
 BENJAMIN FRANKLIN, also made
a similar observations about a
material being attracted to another
material due to charged particles.
 His famous kite-flying experiment
proved that the lightning is a form of
electrical discharge.
 Franklin attached a metal key to the
bottom of a kite string. He observed
sparks jumping off from the metal key
and traveling to his hand holding the

42. Friction is the force that resists relative
motion between two rubbing bodies. The
particles of the material that were
transferred are referred to CHARGE
PARTICLES. The results of the subsequent
experiments led to the development of
the LAW OF CHARGES, which states that
« like charges repel, while unlike charges
attract »
B. ELECTRIC CHARGES

43. C. Charging Process
 For a neutral object to gain either a
negative or a positive charge,
electrons must be allowed to
transfer.
 This could be done in three
different methods, namely,

44. C. Charging Process
 When two materials are rubbed against each other,
their electrons are forced to transfer.
 The material that LOSES the electron becomes
positively charged while the other materials that
GAINS the electrons becomes negatively charged.
 Since the two bodies now carry unlike charges they
attract each other.
1. CONDUCTION

45. C. Charging Process
 The method of charging a body
through contact and friction
between two materials is called
CONDUCTION
1. CONDUCTION

46. C. Charging Process
 Its is the method of electric charge transfer in which a
body that initially charge is brought near an
uncharged body.
 The charged body attracts the opposite charges in the
other body, thereby producing a net charge in it.
 When the charging body is moved away, the charged
body returns to its original uncharged condition.
2. INDUCTION

47. C. Charging Process
 Electric charging can also be done by
GROUNDING or by connecting a charged body
to the ground, a large conductor or deposit of
charges.
 The charged body is connected to the ground
with a conducting wire, through which
3. Grounding

48. C. Charging Process
 It is important to note that
during the charging process,
the charges are not created nor
destroyed. They are only
transferred from one body to
another.