2. Smart Science
GRADE 3
TEXTBOOK
Philippine Copyright 2009 by DIWA LEARNING SYSTEMS INC
All rights reserved. Printed in the Philippines
Editorial, design, and layout by University Press of First Asia
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ISBN: 978–971–46–0089–8
REVIEWER
Marina Balce was a former assistant dean and associate professor at the College of Education, La
Salle College–Antipolo. She taught biological sciences for Psychology students and thesis writing for
graduating Education students in the same college. She was also a Trainee of the Japan International
Cooperation Agency (JICA) at the Aichi University in Nagoya, Japan, where she attended a special
training on Practical Work in Elementary School Science. Dr. Balce finished her bachelor’s degree in
Secondary Education major in Biology at the University of the East–Manila. She has a master’s degree
in Biology Education from the De La Salle University–Manila and a doctorate in Science Education
major in Biology from the University of the Philippines–Diliman.

3. To the Learner
Do you ask yourself questions about the world you live in?
Do you wonder about what lies beyond the blue skies or what
rests below the seas? Do you ask questions about the blooming
trees and colorful flowers you see, the heat and cold you feel,
or the various scents you smell? Do you wonder about the sun,
the moon, and the stars? Your young, active mind has so many
questions because you are curious about so many things.
This book will help you discover the answers to the
questions you have about yourself, the world, and everything
beyond it. This book will be your constant companion as you
unlock the many mysteries of life through various learning
experiences. Moreover, this book will teach you how to apply the
wonders of science to your day-to-day activities.
Let this book help you find the answers to the questions you
have about yourself, your world, and your universe. Let this take
you a step closer to understanding life and in discovering the
wonders of science!

4. Unit 1 You and Your Body
Chapter 1 Your Senses
Lesson 1 Your Eyes ................................................................................................... 2
Lesson 2 How You See Things ................................................................................. 6
Lesson 3 Common Eye Disorders and Diseases .........................................................9
Lesson 4 Taking Care of Your Eyes ..........................................................................15
Lesson 5 Your Ears ..................................................................................................18
Lesson 6 Common Ear Diseases ..............................................................................23
Lesson 7 Taking Care of Your Ears ...........................................................................27
Lesson 8 Your Nose ................................................................................................31
Lesson 9 Common Nose Diseases ...........................................................................35
Lesson 10 Taking Care of Your Nose .........................................................................38
Lesson 11 Your Tongue .............................................................................................40
Lesson 12 Taking Care of Your Tongue .....................................................................44
Lesson 13 Your Skin ..................................................................................................46
Lesson 14 Common Skin Diseases .............................................................................50
Lesson 15 Taking Care of Your Skin ..........................................................................53
Think Back ..................................................................................................................55
Measure Up! ..................................................................................................................55
Chapter 2 Growing Up
Lesson 1 Signs of Growing Up ................................................................................57
Lesson 2 You Grow Up with Friends .......................................................................62
Lesson 3 You Become Smarter as You Grow ...........................................................65
Lesson 4 Having a Healthy Body .............................................................................67
Lesson 5 Diseases and Your Growth ........................................................................71
Lesson 6 Growing Up with Fun ...............................................................................74
Lesson 7 Your Environment Affects Your Growth ....................................................78
Lesson 8 Good Health Habits ..................................................................................81
Think Back ..................................................................................................................84
Measure Up! ..................................................................................................................85
Unit 2 Animals and Plants
Chapter 3 Animals in the Environment
Lesson 1 Animals Move in Different Ways ..............................................................88
Lesson 2 Animal Habitat .........................................................................................92

5. Lesson 3 Kinds of Animals .......................................................................................97
Lesson 4 How Animals Get Their Food .................................................................101
Lesson 5 Food That Animals Eat ............................................................................105
Lesson 6 Animals Have Needs ..............................................................................110
Lesson 7 Useful and Harmful Animals ...................................................................114
Lesson 8 Taking Care of Animals ...........................................................................118
Lesson 9 Safety around Animals ............................................................................122
Think Back ................................................................................................................125
Measure Up! ................................................................................................................126
Chapter 4 Plants around You
Lesson 1 Similarities and Differences among Plants ...............................................128
Lesson 2 Where Plants Grow .................................................................................133
Lesson 3 Parts of Plants .........................................................................................137
Lesson 4 How Plants Grow ...................................................................................141
Lesson 5 Importance of Plants ...............................................................................145
Think Back ................................................................................................................150
Measure Up! ................................................................................................................151
Unit 3 Matter, Energy, Force, and Motion
Chapter 5 Matter around You
Lesson 1 Solids ......................................................................................................154
Lesson 2 Liquids ....................................................................................................158
Lesson 3 Gases ......................................................................................................162
Think Back ................................................................................................................164
Measure Up! ................................................................................................................165
Chapter 6 Light and Sound
Lesson 1 Light Travels ...........................................................................................166
Lesson 2 Light Bounces .........................................................................................171
Lesson 3 Light Bends .............................................................................................173
Lesson 4 Colors of White Light ..............................................................................176
Lesson 5 How Sound Is Produced .........................................................................179
Lesson 6 Loud and Soft Sounds .............................................................................182
Lesson 7 Sound Travels .........................................................................................185
Think Back ................................................................................................................188
Measure Up! ................................................................................................................189

6. Chapter 7 Force and Motion
Lesson 1 Making Objects Move .............................................................................191
Lesson 2 The Force of a Magnet ............................................................................194
Lesson 3 Earth’s Force ...........................................................................................197
Lesson 4 Forces of Wind and Water ......................................................................200
Think Back ................................................................................................................204
Measure Up! ................................................................................................................205
Unit 4 Earth and Sun
Chapter 8 Soil and Water
Lesson 1 Your Environment ...................................................................................208
Lesson 2 Characteristics of the Soil ........................................................................211
Lesson 3 Useful Soil ..............................................................................................215
Lesson 4 Soil Pollution ..........................................................................................218
Lesson 5 Caring for the Soil ...................................................................................222
Lesson 6 Sources of Water .....................................................................................224
Lesson 7 Uses of Water .........................................................................................229
Lesson 8 Water Pollution .......................................................................................232
Lesson 9 Using Water Wisely ................................................................................235
Think Back ................................................................................................................237
Measure Up! ................................................................................................................238
Chapter 9 The Weather and the Sun
Lesson 1 Air Temperature, Wind, and Air Pressure ................................................240
Lesson 2 Humidity, Clouds, and Precipitation .......................................................246
Lesson 3 You and the Weather ..............................................................................252
Lesson 4 Weather and the Environment .................................................................256
Lesson 5 Protection from Harsh Weather Conditions .............................................259
Think Back ................................................................................................................263
Measure Up! ................................................................................................................264
Bibliograpy ................................................................................................................266

7. Your body is composed of many parts. Some of these body parts are
your sense organs. These include your eyes, ears, nose, tongue, and skin.
You can see, hear, smell, taste, and feel because of your senses.
Your body changes as you grow up. As this happens, many things
about you also change. You become more interested in the things around
you. You want to compare or differentiate things. You start to practice good
health habits. You start to make new friends. These things happen because
you are growing up.

8. Chapter 1
Your Senses
It is good to observe the things around you.
You see the sky in bright hue.
And hear the cows that moo!
You can smell the flowers in the garden
Or taste your favorite food in the kitchen
Or feel the cool breeze on the mountain.
You see, hear, smell, taste, and feel.
Your sense organs allow you to experience these in real!
Lesson 1
Your Eyes
1. What is your organ for seeing?
2. What are the parts of your eyes and their functions?
Your eyes are your organs
for seeing. You can see different
things around you because
of your eyes. You can see the
different colors of flowers. You
can watch the spider spin its
web. You can see your friends.
You can read books. You can
watch your favorite TV program.
What other things can you see
around you?
2 Smart Science 3

9. Parts of the Eye
1. Face your seatmate.
2. Look at one of his or her eyes.
3. Draw its shape.
What is its color? _________
4. Look at the drawing below. Can you name the parts shown?
Choose from the words in the box.
a. __________________
pupil
b. __________________
eyebrow
iris c. __________________
eyelashes d. __________________
eyelid
e. __________________
Each part of the eye has a aqueous humor retina
function. There are parts that
protect the eyes. These are the pupil optic
eyelids, the eyelashes, and the nerve
eyebrows. They protect the eyes
from dust, too much light, and cornea
other things that can damage
them. iris
The inside of the eye has
lens
other parts. Examine the drawing. vitreous
humor
It shows a longitudinal section of eye muscle
the eye.
Longitudinal section of the human eye
The part of the eye that is
shaped like a ball is the eyeball. It is the part that we call the eye. It
contains a jellylike substance called the vitreous humor, which gives the
eye its round shape.
You and Your Body 3

10. The eyeball can move in its socket. The muscles that are attached to it
let the eye move. Close your eyes and gently touch your eyeballs as they
move up and down. What characteristics of the eyeball can you infer by
this action?
Do you see the colored part of the eye? It is called the iris. The iris is
made up of muscles. At its center is the pupil, an opening that allows light
from the outside to enter the eye.
Look at the drawings of the eyes below. Tell the difference between
the pupils of each pair of eyes.
In bright light, the pupils of the eyes In dim light, the pupils of the eyes
become smaller. become larger.
The muscles in the iris make the pupil smaller or bigger. In bright light,
the iris muscles tighten, making the opening (pupil) smaller. A smaller
opening prevents too much light from entering the eye. This way the eye is
protected. In dim light, the pupil becomes bigger to let in more light.
Behind the pupil is the lens. Light can pass through it because it is
transparent. A tough, transparent material called the cornea covers the
lens. Between the lens and the cornea is a watery fluid called the aqueous
humor.
At the back part of the eye is a light-sensitive layer called retina. The
cells in the retina translate the light that enters the eye into a signal. This
signal is then carried to the brain by the optic nerve for processing.
• The eyes are the sense organs for seeing.
• Eyelids, eyelashes, and eyebrows protect your eyes from dust, too much
light, and other damaging things.
• The inside parts of the eyes are the iris, pupil, lens, cornea, vitreous
humor, aqueous humor, retina, and optic nerve.
4 Smart Science 3

11. A. Match the items in Column A with those in Column B. Write only the
letter of your answer.
Column A Column B
______1. pupil a. covers the lens
______2. aqueous humor b. an opening that allows light
______3. eyeball to enter
______4. cornea c. generally referred to as
______5. lens the eye itself
______6. eyelid d. colored part of the eye
______7. vitreous humor e. gives the eye its round shape
______8. iris f. its transparency allows
light to pass through it
g. protects the eyes from dirt
h. watery fluid between the
cornea and the lens
i. translates light into signal
B. Make a model of the eye. Use recycled materials to make the model.
You and Your Body 5