2. ENERGY AT WORK In early times, man relied entirely on his
muscular energy to do some kind of work. Later on, he was able to
supplement his energy with those of some animals such as horse,
ass, ox and camel. Then, he discovered other natural sources of
energy and invented some simple machines which helped him make work
easier and faster. What is energy? What are the different forms of
energy? Do you have energy? What is this energy you have? Can you
create energy from nothing? How does man change one form of energy
into another form of energy to make it more useful to him?
3. ENERGY AND WORK Lesson 1
4. ENERGY AND WORK Energy exists in all matter in your
environment. A rock on a hill, a swinging pendulum or even a fruit
on a tree possess some kind of energy. It depends upon whether or
not the energy is used or is just waiting to be used. What is
energy? How is energy related to work? I was not able to sleep well
last night. I seem not to have enough energy for work or play
today. Remember we have a test in Math today. Weve got to work on
some problems to pass it.
5. WHAT IS ENERGY? Energy is the ability or capacity to do
work. To understand energy, you have to understand what work means.
To a scientist, work does not mean trying to solve mathematical
problems or stand at attention for five to ten minutes. Work is
motion against resistance. When you lift a box against gravity or
drive a nail into a board against friction, you have done work. In
doing work, energy is used up. Both work and energy are measured
according to the distance an object is moved. A force must be
overcome to keep the object moving. Suppose you lift one pound of
iron one food. Since work is equal to force times distance (w=f x
d); then, you have done one food-pound of work and you have used up
one foot-pound of energy also.
6. TWO KINDS OF ENERGY There are two kinds of energy which can
do work in various ways. These are kinetic energy and potential
energy. Kinetic comes from a Greek word meaning motion. Kinetic
energy is the energy possessed by bodies in motion. A rolling ball
can move another ball which is at rest. When you drive a spade into
the ground, you work against the resistance of hard soil. You drop
a weight that does the work; it has kinetic energy. While you are
holding the spade high in the air, its ability to do work is only
potential because of its position. It has potential energy or
stored energy. Potential energy is the energy possessed by a body
because of its position, condition or state.
7. When you wind up a toy car, the spring winds tighter and
tighter. The spring possesses potential energy. When you let the
car go, the spring unwinds and the car speeds away. It now has
kinetic energy. The rock at the edge of a hill, the water held back
by a dam and a hammer held up to drive a nail into the wood possess
gravitational potential energy. The rock on the hill has en energy
equal to the energy it has once it starts rolling down. When the
hammer is dropped, it releases an amount of energy equal to the
energy you exert to raise it.
8. REMEMBERING SCIENCE FACTS Energy is the ability of capacity
to do work. Work is motion against resistance. Work is force times
distance. Kinetic energy is possessed by bodies in motion.
Potential energy is stored energy possessed by a body because of
its position, condition or state.
9. TRUE OR FALSE? 1. Without energy, work cannot be done. 2. No
work is done if there is no motion over a distance. 3. A person
standing still under the sun for an hour is doing work. 4.
Potential energy is stored energy. 5. Work is equal to the force
needed to move it at some distance.
10. FORMS OF ENERGY Lesson 2
11. FORMS OF ENERGY Everyday you make use of different forms of
energy. These forms of energy may either come from natural or
artificial sources. The pictures show examples of different forms
of energy you observe around you. What are the different forms of
energy? How is each energy formed and used?
12. RADIANT/ LIGHT ENERGY Lesson 2.1
13. RADIANT/LIGHT ENERGY The sun shines on earth all the time.
It is a tremendous source of radiant or solar energy. Without the
heat or light from the sun, the earth would be a cold and dead
planet. This radiant energy nourishes all life. Radiant energy from
the sun travels out into space from all directions. In 100 minutes,
the earth receives as much energy from the sun as is used by all
the countries on earth in one year. Light energy from the sun can
travel through empty space. A ray of light can be broken down into
many colors.
14. The most useful form of solar or radiant energy reaches the
earths surface in the form of light. Green plants have used
sunlight for hundreds of millions of years in photosynthesis.
Through photosynthesis, plants make sugar and starch or
carbohydrates from the carbon dioxide and water in the air and
soil. Chloroplasts, the green chemical within plants, make
photosynthesis happen. Coal, oil and natural gas got their energy
from plants too. Coal is formed from dead plants while oil and
natural gas are formed from decayed bodies of animals which died
hundreds of millions of years ago.
15. Color is determined by the wavelength of the light. But the
light waves that your eyes can detect are only limited to the
colors of visible white light. The shortest waves your eyes can see
are those of violet and the longest are of red. In between these
are all the colors of the spectrum. A beam of white light can be
dispersed into a spectrum through a prism. Most of the colors you
see in your surroundings are not of a single wavelength. They are
mixtures of many wavelengths. When white light falls on an object,
some wavelengths are reflected. The rest are absorbed by the object
itself. The reflected wavelengths are the colors your eyes can see
of the object.
16. Each kid of material has its own pattern of spectrum lines.
Once these patterns are known, they can be used to tell which
materials are present in a sample. Chemists call this
spectrochemical analysis of a substance. The spectrum can identify
a substance from only a tiny speck. This method is used in chemical
plants, steel mills and even in police work. Astronomers also make
use of the spectrum. A spectroscope is attached to a large
telescope to find out the chemical make up of distant planets,
stars, clouds of gas and other objects in the sky. It can also tell
how fast a star or other light source is moving. Light waves from a
light source that is moving toward the earth are crowded up and
appear a little shorter. Waves from a source that is moving away
appear to be longer and are stretched out. This is called Doppler
effect.
17. Light energy travels in the form of waves or rays described
as electromagnetic waves. Light waves are made up of electrical and
magnetic forces traveling together. The arrangement of these
electromagnetic waves in order of their wavelengths is called the
electromagnetic spectrum. The spectrum consists of radio waves,
infrared waves, microwaves, visible light, ultraviolet rays, x-rays
and gamma rays.
18. INFRARED WAVES Infrared waves are given off strongly by
glowing, hot objects such as the sun, electric lamps and flames.
Even electric irons and hot pavements send out strong infrared
radiation.
19. ULTRAVIOLET RAYS Ultraviolet rays or waves are shorter than
those of violet light. When ultraviolet rays strike certain
fluorescent minerals, oils and plant juices, they are changed to
longer waves which are visible. Hen you stay under the sun for a
long time, ultraviolet rays cause sunburn on your skin. However in
small amounts, they form Vitamin D in the skin. Ultraviolet
radiation kills bacteria. It is used in purifying foods, water and
even air. Police scientists use ultraviolet light for detecting
blood- stain, forged documents and faked oil paintings.
20. X RAYS AND GAMMA RAYS X rays and gamma rays are used to
locate and destroy harmful growths of cancer cells and tumors.
Engineers use them to locate defects inside metal machine parts.
Microwaves are used in microwave cooking, in communications and
radar.
21. REMEMBERING SCIENCE FACTS The sun is the greatest source of
radiant or solar energy. The most useful form of solar energy is
light which travels in waves or rays. Light waves are made up of
electrical and magnetic forces traveling together. This is called
electromagnetic spectrum. The eyes can only see visible white
light.
22. IDENTIFY THE WORD BEING DESCRIBED 1. It is used to disperse
the colors of white light. 2. These are waves given off by hot,
glowing objects. 3. They cause sunburn on your skin due to
overexposure to these light rays. 4. It is a device used by
astronomers to study distant stars, planets and clouds of gases. 5.
These are the only light waves that eyes can see. 6. These rays are
used to locate and destroy harmful growths of cancer cells. 7.
These are light waves used in cooking. 8. It is an effect wherein
waves from a source which is moving away seem longer. 9. It is fuel
formed from dead plants. 10. It is the most useful form of solar or
radiant energy.
23. SOUND ENERGY Lesson 2.2
24. SOUND ENERGY Your world is full of different kinds of
sounds the sweet voice of your teacher, the chirping of a bird, the
irritating horn of a bus and even the buzzing of a mosquito or bee.
Each sound is different from one another. Each has a distinct sound
which enables you to tell or identify it from other sounds. How is
sound produced? How does it travel? How does man make use of sound
energy?
25. SOUND ENERGY Sound energy is another common but very useful
form of sound. Sounds are all produced by back and forth motion
called vibrations. Vibrations are the source of all sounds. A
vibrating object sends out sound waves through the air in all
directions. The waves travel outward in ever widening shells. They
look somewhat like round balloons of different sizes, one inside
the other. The balloons represent the compressions of air
molecules, and the space between the balloons represent the
expansions. The source of the sound would be in the center of the
smallest balloon. Scientists call these waves compression
waves.
26. Sound travels from vibrating object by means of a sound
carrier or medium. This medium may be a solid, liquid or a gas. Air
is the most common carrier of sound. The speed of sound is slower
than the speed of light. The speed of sound depends on its medium.
In steel and aluminum or other solids, sound travels fastest. It is
15 times faster than it is in air and about 4 times as fast as in
water or liquids. Changes in temperature of the medium can also
change the speed of sound. In warm air, for example, sound travels
slightly faster than in cold air.
27. Sound waves are described as being of low, medium and high
frequency. Frequency is the number of vibrations per second. It is
measured in hertz. Short wavelengths have a high frequency and long
wavelengths have a low frequency. The pitch of sound depends on its
frequency. A high frequency produces a high pitch while a deep
rumbling sound has a low pitch.
28. Sounds can also be soft or loud. The loudness of the sound
depends on each persons sense of hearing; and is therefore
difficult to measure. So, scientists instead measure the intensity
of sound. Intensity refers to the amount of energy in the sound.
Intensity is measured in units called decibels. One decibel is the
smallest change in intensity that can be detected by most people. A
whisper loud enough to be heard 5 feet away is 20 decibels while
traffic on a busy street is 80 decibels. A sound level of 120 or
more decibels is painful to the ears of most people.
29. Sound waves can behave in ways that produce a number of
different special effects. Those effects may cause the sound to be
repeated or to be louder or blurred. Echoes are reflected sounds.
In order for you to detect a definite echo, the reflecting surface
must be at least 55 feet or 16 meters away from you. Sometimes,
sounds are reflected many times and so the original sound is
repeated many times. No distinct or separate echoes are heard. This
is called reverberation. A certain amount of reverberation is
necessary in auditoriums, especially for the enjoyment of
music.
30. The human ear generally cannot hear sound waves whose
frequency is higher than about 20,000 hertz. Such high-frequency
waves are called ultrasound or ultrasonic waves. Ultrasonic waves
have as high as millions of hertz which can never be heard by a
person. Bats, dogs and dolphins can hear ultrasonic sounds.
Scientists use straight ultrasonic beams called sonar to locate
submarines, schools of fish and other solid objects under water. In
industry, ultrasound is used to detect flaws hidden deep inside the
metals or other solid materials; shake up paint mixtures,
homogenize milk and clean tools, machine parts and other solid
objects. In medicine, it is used to help detect brain injuries and
for certain kinds of surgery. Ultrasonic holography, a method of
producing three dimensional pictures, safely detects the form of an
unborn baby inside its mothers womb. In dentistry, a dental drill
controlled by ultrasonic vibration can cut into tooth enamel
without hurting the gum tissue.
31. REMEMBERING SCIENCE FACTS Sounds are produced by back and
forth motion called vibrations. The speed of sound is slower than
the speed of light. Sound travels through a medium. Frequency of a
sound is the number of vibrations per second. It is measured in
hertz. The pitch (highness or lowness) of a sound depends upon
frequency. Intensity refers to the amount of energy in the sound.
It is measured in units called decibels. Echoes are reflected
sounds. Reverberation are sounds which are reflected many times. No
distinct echo is heard. Ultrasonic sounds are high frequency sounds
which can never be heard by a person. These are used in industry,
medicine, dentistry and even military work.
32. MECHANICAL ENERGY Lesson 2.3
33. MECHANICAL ENERGY You love to run, walk, skip and play
games. What games do you enjoy playing with your friends? How is
your body able to do all these movements? In what other ways do you
move your body? What kind of energy enables you to do all these
things?
34. When you eat, the food is slowly burned in the cells of
your body. It is released so that your muscles can move. This is
called mechanical energy. Whenever something moves, it has
mechanical energy. The energy of moving or falling bodies produces
some kind of energy called mechanical energy. Mechanical energy
comes from the fact that matter has weight and is in motion.
35. A wound-up spring is another source of mechanical energy.
Because of the elasticity of the metal of the spring, it bends to
uncoil. When it does so, it gives off mechanical energy which turns
the hands of uncoil or makes the toy car move. Most of the machines
today work because of mechanical energy. Some of these machines are
used for lifting and construction purposed. Some are used in
transportation such as cars, buses, trains and airplanes. These
means of transportation depend mostly on mechanical energy.
36. REMEMBERING SCIENCE FACTS Mechanical energy is the energy
of moving or falling bodies. Many of the machines you use work
because of mechanical energy.
37. ELECTRICAL ENERGY Lesson 2.4
38. ELECTRICAL ENERGY Matter is made up of tiny particles
called atoms. An atom is made up of even smaller particles which
are the electrons, protons and neutrons. Each electron carries a
negative electrical charge. The proton carries a positive charge
and the neutron has no charge. An atom usually has the same number
of protons and electrons. Thus, the positive and negative charges
balance each other, making the atom electrically neutral. But,
there is an electrical field of force around charged bodies. This
electrical field is the source of electrical energy.
39. Bodies which have the same electrical charges repel each
other. Bodies which have unlike electrical charges attract each
other. This is the law of electrical charges. The attraction and
repulsion between charged bodies is caused by electrical energy. In
an electrical copper wire, an electrical field of force exists
between the two ends of the wire. If the electrical field is strong
enough, some of these electrons fly away from their atoms and flow
to the positively charged end of the wire. This flow of electrons
is called electric current. The electrons move because of
electrical energy.
40. Electrical energy is used in every home. When you plug in a
television, you get electrical energy that runs through wires.
These wires run from outlets in your home to electrical power line.
These power lines go to the electrical power plant where energy is
made. The generator runs big turbines which produce electricity
from flowing water. Electrical energy can also be made from
chemical energy through dry cells or batteries. Recall the many
activities you have done wherein you used batteries to do
work.
41. REMEMBERING SCIENCE FACTS Matter is made up of tiny
particles called atoms. Atoms are made up of electrons, protons and
neutrons. The electrical field of force around charged bodies is
the source of electrical energy. Moving or flowing of electrons is
called electric current.
42. TRUE OR FALSE? 1. Electrical energy causes the attraction
or repulsion of charged bodies. 2. Falling or flowing water
possesses mechanical energy. 3. The flow of electrons is called
electric current. 4. Same electrical charges attract while unlike
electrical charges repel. 5. Ultrasonic sounds cannot be heard by a
person. 6. The electrical field of force is the source of
electrical energy. 7. An atom is made up of thousands of neutrons.
8. Mechanical energy is energy in motion. 9. Batteries/ dry cells
get their electrical energy from chemical substances. 10.
Electrical energy is used in almost every home.
43. HEAT ENERGY Lesson 2.5
44. HEAT ENERGY Everyday, you use the words hot and cold. Hot
means having a lot of heat while cold means having very little or
no heat at all. Your life and every living thing depend on heat;
for without heat, you will freeze. Life on earth is made possible
because of the heat given off by the sun and heat lost to cooler
surroundings. Man has known about heat for a long time when he
discovered fire. Soon, he learned to use it to keep him warm and
cook his food. He was able to release the suns heat trapped in
fossil fuels such as wood, coal and oil. He learned that heat is a
type of energy that can be made to do work. What is heat energy?
What are the uses of heat energy?
45. Anything that is in motion has energy. All matter contains
heat energy. Heat energy is the energy of molecules in random
motion or motion with no particular direction. If heat energy is
added to matter or substance, its molecules move fasted and the
substance becomes hotter. If matter loses heat energy, its
molecules move slow an the substance becomes colder. Heat is energy
that travels from warm bodies to cooler bodies. The states of
matter can be explained according to this theory. When enough heat
is added to a solid, its molecules move faster until it melts and
becomes liquid. If more heat is added, its molecules move even
faster until it becomes a gas.
46. Adding heat generally causes matter to expand in volume or
size. Heat causes the molecules to move faster and farther apart.
The substance takes up more space. Taking heat causes matter to
become smaller in volume since the molecules move slower and come
closer together. The substance takes up less space. An even greater
change in volume takes place when the heat causes a liquid to
become gas. When you boil water in a kettle, some of the water
changes to steam or gas. Has takes up more space so the kettles lid
is pushed up and whistles.
47. Heat also affects gas pressure. Adding heat increases the
speed of the gas molecules and the force which these molecules
exert on the walls of their container. Taking away heat reduces the
speed of the molecules and so, also the gas pressure. Using this
theory, heat energy is put to work in a steam engine which was used
to run boats, trains and other means of transportation.
48. Heat tells how much energy is flowing into or out of the
object. The amount of heat given off or absorbed by and object is
measured in calories and kilocalories. A calorie is the amount of
heat that must flow into a gram of water to raise its temperature
one Celsius degree. A kilocalorie is 1,000 calories. It is used in
reference to food energy and should be written with a capital C. A
calorimeter is an instrument used to measure the amount of heat
given off or absorbed by a body. It is these Calories on which the
human body depends for its energy.
49. Heat energy has made civilization possible. Industry grew
as man learned to make greater use of metals and fossil fuels such
as coal, iron and natural gas. Engines which change heat energy
into mechanical energy were invented. Technology has prospered
because of mans discovery of putting heat energy to work. Name all
of the sources of heat energy at home. How do you use each
one?
50. REMEMBERING SCIENCE FACTS Heat energy is the energy of
molecules in motion. Heat tells how much energy is given off or
absorbed by an object. It is energy that travels from warm bodies
to cooler bodies. A calorimeter is an instrument used to measure
the amount of heat energy in calories (c) or kilocalories (C).
51. CHEMICAL AND NUCLEAR ENERGY Lesson 2.6
52. Study the pictures. Each picture shows some kind of energy
which is capable of doing work. This energy is called chemical
energy. Chemical energy is stored in the food you eat. There is
also chemical energy in a lighted match and in the gasoline being
placed in the cars tank. What is chemical energy? Is nuclear energy
also a form of chemical energy? How does man make use of these
forms of energy?
53. There is chemical energy in the food you eat. This food
undergoes chemical changes as it goes from the mouth to the stomach
and other parts of your body. The soluble food has chemical energy
which is used by your body to do different bodily functions.
Besides food, paper, wood, coal and gasoline also have chemical
energy. When these things are burned, this chemical energy is
released.
54. Chemical changes go on all about us. Whenever coal or iron
burns, iron rusts or when food is cooked, chemical changes take
place. Chemical changes also go on inside your body all the time.
Chemical energy causes atoms of two or more molecules to unite and
form molecules of another substance. When the atoms of a molecule
are separated or recombined, heat energy is absorbed or released.
You call this combustion which may either be slow as in rusting of
iron or spontaneous as in an explosion of dynamite.
55. The heat produced by chemical energy as a fuel is used to
warm homes and cook food. Heat from burning fuel is used to operate
machines such as a steam turbine. The heat produced by burning
gasoline makes the car run.
56. NUCLEAR ENERGY Nuclear energy is the energy contained in
the center or nucleus of an atom. It is the most powerful source of
energy that man has discovered. Nuclear energy can be released in
two types of reactions: fusion (the joining of two nuclei) and
fission( the splitting of a nucleus). Nuclear energy is used in
scientific research and in medical treatments. It is used to
produce electricity through the nuclear power plant. It powers
satellites and submarines. Some people have invented nuclear
weapons for destruction uses. Scientists continue to experiment
with nuclear fusion. Fission fuels used in nuclear reactors such as
uranium and plutonium can be exhausted. But, fusion fuels are
plentiful. Deuterium can be extracted from seawater and can provide
an almost limitless source of energy.
57. REMEMBERING SCIENCE FACTS Chemical energy causes atoms to
unite and form a molecule of another substance. Chemical change
takes place and heat energy is released or absorbed. Nuclear energy
is the energy contained in the center or nucleus of an atom. It is
released either through fusion or fission.
58. MATCH COLUMN A AND BA B 1. Fission fuel used in nuclear
reactor a. Plutonium 2. Instrument used to measure heat b. Electric
current 3. Energy that travels from warm bodies to cooler bodies c.
Mechanical energy 4. Flow of electrons d. Fusion 5. Kind of
reaction wherein two nuclei are joined e. Uranium 6. Energy
possessed by moving or falling bodies f. Calorimeter 7. Tiny
particles which make up matter g. Heat energy 8. Amount of heat
needed to raise the temperature of one gram of water one degree
Celsius h. Kilocalorie k. molecule 9. Energy stored in the food you
eat i. Calorie l. chemical energy 10. A fusion fuel which can be a
limitless source of energy j. Atom m. deuterium
59. FROM ONE FORM OF ENERGY TO ANOTHER Lesson 3
60. FROM ONE FORM OF ENERGY TO ANOTHER Around you, changes in
the forms of energy occur everyday. These are called energy
conversions. One form of energy is changed or transformed into
another form because some materials or devices act as energy
converters. When man discovered fire, he changed chemical energy of
wood into heat and light. Radiant energy from the sun is changed
into chemical energy by plants. Kinetic energy of the wind is
changed into mechanical energy to drive windmills.
61. DESCRIBE THE CHANGE OF ENERGY FROM ONE FORM TO ANOTHER Is
heat absorbed or released as one form of energy changes into other
forms?
62. One kind of energy can always be changed into another. In
an electromagnetic net, electrical energy is changed into
mechanical magnetic energy. Chemical energy of burning fuels is
turned into heat and light energy. In an electric light, electrical
energy is changed into heat and light energy.
63. All your appliances at home have electric motors. They
change electrical energy into mechanical energy. They provide power
for electric fans, vacuum cleaners and washing machines. They
change electrical energy into heat energy in stoves, oil burners,
refrigerators and air conditioners. These appliances make life
easier and more pleasant for you.
64. Using todays advanced technology, electrical energy is
changed into sound and light energy. Inexpensive digital
synthesizers have made electronic music accessible to more people.
Now, you can play the organ to duplicate the sounds of an entire
orchestra. Through semiconductors, electronics have made radio and
television communication available in every corner of the world.
Computers make your life more productive, convenient and
entertaining. Powerful computers aid engineers in designing cars
and houses. Electronic banking machines allow people to take money
from their account anytime. Computerized scanners speed supermarket
checkout by reading product bar codes.
65. Hospitals use electronic equipment such as x-ray machines,
magnetic resonance imaging (MRI) devices and computer aided
tomography (CAT) scanners to detect injury or disease. Radiation is
a by product of nuclear energy which can be in the form of alpha,
beta and gamma rays. Radioisotopes emit radiation. With it, very
minimum nuclear energy is changed into chemical energy which can
improve some varieties of rice and prolong the shelf life of fruits
like mangoes and bananas. Nuclear energy can also be changed into
heat electrical and mechanical energy through the nuclear
reactor.
66. The food you eat has chemical energy. Part of this chemical
energy is changed into mechanical energy which enables you to move
or do other body functions. Some chemical energy is turned into
other forms of chemical energy which your body uses to build up or
repair cells and tissues. It is changed into sound energy in your
voice box when you talk or sing. All kinds of energy are easily
changed into heat. Heat is the basic and simplest kind of energy.
Because all other forms of energy can be changed to heat, energy is
often measured in terms of heat.
67. REMEMBERING SCIENCE FACTS oEnergy may be changed from one
form into another. oWhenever energy is changed from one form to
another to do work, some energy is changed into heat.
68. LAW OF CONSERVATION OF ENERGY Lesson 4
69. LAW OF CONSERVATION OF ENERGY Living things make use of
energy. Would you believe that you use up thousands of kilocalories
of energy everyday? Even when you sleep or rest, your heart beats
and moves the blood. You breathe too. Your energy must come from
somewhere. Do you remember where this energy comes from ? What
happens as energy is changed from one form to another? Is there
some energy gained or lost during the change?
70. When you dribble a basketball, it hits the floor and rises
again. As it bounces, it falls short of the height it reached the
time before. After some time, it dribbles along the ground and
comes to a stop. Has it lost its kinetic energy? What happens to
this energy? As the ball bounces, some of its kinetic energy is
used to push the air aside which turns into heat. The rest of the
energy heats up the ball and the ground. Soon, all the kinetic
energy turns into heat which spreads through the air and
ground.
71. When you turn off the heat of boiling water, the water
starts to cool down to room temperature. The heat energy is not
lost. It just spreads out through the air. Energy may be changed
from one form to another; it is never created and never destroyed.
This is called the law of conservation of energy. This is also
known as the first law of thermodynamics. Thermodynamics is the
study of all forms of energy. So, the energy never appears out of
nowhere. It has to come from somewhere. Energy cannot be made out
of nothing.
72. In using energy, you do not destroy it. You just change it.
When you stay under the sun, the radiant energy from the sun is
turned into heat. Your body gets rid of this heat when you perspire
or sweat which is later turned into vapor. This way, heat energy is
turned into chemical energy. This makes you feel cool and
comfortable. Heat flows from higher temperatures to lower
temperatures. Then heat spreads out evenly. This spreading out
evenly of available energy is called entropy by scientists.
However, it will take billions of years before all the energy in
the universe will spread out evenly.
73. REMEMBERING SCIENCE FACTS Law of conservation of energy
states that energy may be changed from one form to another; but it
is never created or destroyed. Thermodynamics is the study of all
forms of energy
74. FOR YOU TO REMEMBER Energy is the ability or capacity to do
work. Work is motion against distance. Work is force times
distance. Kinetic energy is stored energy possessed by bodies in
motion. Potential energy is stored energy possessed by a body
because of its position, condition or state. The sun is the
greatest source of radiant or solar energy. The most useful form of
solar energy is light which travels in waves or rays. Light waves
are made up of electrical and magnetic forces traveling together.
This is called electromagnetic spectrum. The eyes can only see
visible white light. Sounds are produced by back and forth motion
called vibrations.
75. The speed of sound is slower than the speed of light. Sound
travels through a medium. Frequency of a sound is the number of
vibrations per second. It is measured in hertz. The pitch (highness
or lowness) of a sound depends upon frequency. Intensity refers to
the amount of energy in the sound. It is measured in units called
decibels. Echoes are reflected sounds. Reverberation are sounds
which are reflected many times. No distinct echo is heard.
Ultrasonic sounds are high frequency sounds which can never be
heard by a person. These are used in industry, medicine, dentistry
and even military work. Mechanical energy is the energy of moving
or falling bodies. Many of the machines you use work because of
mechanical energy.
76. Matter is made up of tiny particles called atoms. Atoms are
made up of electrons, protons and neutrons. The electrical field of
force around charged bodies is the source of electrical energy.
Moving or flowing of electrons is called electric current. Heat
energy is the energy of molecules in motion. Heat tells how much
energy is given off or absorbed by an object. It is energy that
travels from warm bodies to cooler bodies. A calorimeter is an
instrument used to measure the amount of heat energy in calories
(c) or kilocalories (C). Chemical energy causes atoms to unite and
form a molecule of another substance. Chemical change takes place
and heat energy is released or absorbed. Nuclear energy is the
energy contained in the center or nucleus of an atom. It is
released either through fusion or fission.
77. Energy may be changed from one form into another. Whenever
energy is changed from one form to another to do work, some energy
is changed into heat. Law of conservation of energy states that
energy may be changed from one form to another; but it is never
created or destroyed. Thermodynamics is the study of all forms of
energy.
