Class 7 Science Chapter 1 NCERT Book - The Ever-Evolving World of Science

 Page 1


The Ever-Evolving World of Science
The Ever-Evolving 
World of Science
1
We hope you enjoyed your adventures with Curiosity in 
Grade 6, and are now ready to continue our journey into the 
wonderful world of science. This again, is not just a textbook with 
facts?—?it is an invitation to question, to perform experiments, 
and to explore, as we try to understand the beautiful world we 
live in. The world of science covers everything?—?small and large, 
near and far. We may be looking at tiny cells inside a leaf, or 
the movement of the sun and the stars. We may be testing out 
the materials around us at home, or discussing how water ? ows 
underground. As you go through the chapters in this book, you 
will start new adventures that challenge your thinking, expand 
your knowledge, and help you become an explorer, making small 
discoveries for yourself. 
Before we dive into our exciting journey, take a moment to 
observe something special about this book. Look at the page 
numbers?—?they follow the playful ? ight of a butter? y and the 
soaring of a paper plane! Just as a butter? y ? utters freely and a 
paper plane ? ies into the sky, learning takes ? ight when curiosity 
leads the way. Did you know that something as simple as a paper 
plane inspired real scienti? c explorations of ? ight? From early 
inventors studying bird wings to modern engineers designing 
aircraft, the dream of ? ying started with simple observations and 
experiments. So, as you turn each page, let your imagination take 
? ight?—?exploring new ideas, discovering wonders, and reaching 
for the skies!
Chapter 1.indd   1 Chapter 1.indd   1 4/3/2025   4:50:06 PM 4/3/2025   4:50:06 PM
Page 2


The Ever-Evolving World of Science
The Ever-Evolving 
World of Science
1
We hope you enjoyed your adventures with Curiosity in 
Grade 6, and are now ready to continue our journey into the 
wonderful world of science. This again, is not just a textbook with 
facts?—?it is an invitation to question, to perform experiments, 
and to explore, as we try to understand the beautiful world we 
live in. The world of science covers everything?—?small and large, 
near and far. We may be looking at tiny cells inside a leaf, or 
the movement of the sun and the stars. We may be testing out 
the materials around us at home, or discussing how water ? ows 
underground. As you go through the chapters in this book, you 
will start new adventures that challenge your thinking, expand 
your knowledge, and help you become an explorer, making small 
discoveries for yourself. 
Before we dive into our exciting journey, take a moment to 
observe something special about this book. Look at the page 
numbers?—?they follow the playful ? ight of a butter? y and the 
soaring of a paper plane! Just as a butter? y ? utters freely and a 
paper plane ? ies into the sky, learning takes ? ight when curiosity 
leads the way. Did you know that something as simple as a paper 
plane inspired real scienti? c explorations of ? ight? From early 
inventors studying bird wings to modern engineers designing 
aircraft, the dream of ? ying started with simple observations and 
experiments. So, as you turn each page, let your imagination take 
? ight?—?exploring new ideas, discovering wonders, and reaching 
for the skies!
Chapter 1.indd   1 Chapter 1.indd   1 4/3/2025   4:50:06 PM 4/3/2025   4:50:06 PM
Curiosity | Textbook of Science | Grade 7
2
Exploration, of course, isn’t just about discovering new facts 
or learning about di? erent things in nature. Science, as we said 
in Grade 6, is a process, so it is about a way of thinking that 
welcomes curiosity, asks questions, and is open to the unknown. 
In Grade 7, we will try to ask deeper questions: How do things 
work? Why do events happen the way they do? And what can 
we learn from the patterns that we see in nature? 
To do this, we have to step out of this book, step out of the 
classroom perhaps, and experience the world through activities 
and experiments. These are experiences that we hope will not 
just be interesting or exciting but also serve as stepping stones 
to a deeper understanding of the environment we live in and of 
our place on this planet. We believe that this will also help you 
to see science as an ongoing process of discovery. And not just 
about discovery alone, but also about responsibility. As young 
science explorers, you will soon see how human activities are 
linked to what happens in the natural world and are connected 
to the society we live in. You will, we hope, also see the role that 
science can play in addressing environmental challenges and 
help in creating a more sustainable world. 
But let’s get back into this book for now. You will read about 
topics in di? erent ? elds of science, from physics and chemistry 
to biology and earth sciences. While they might appear as 
di? erent chapters, just as we had said in Grade 6, they are 
all interconnected. Scienti? c ideas in one area often inspire 
discoveries in another, or at least allow us to ask questions in 
another area. So, let’s take a quick journey through our book for 
this year. We will start by looking at the properties of materials 
around us, mostly the things we experience but perhaps never 
ask questions about?—?why are some fruits sour? What happens 
when we wash a haldi stain on our school uniform? 
Chapter 1.indd   2 Chapter 1.indd   2 4/3/2025   4:50:07 PM 4/3/2025   4:50:07 PM
Page 3


The Ever-Evolving World of Science
The Ever-Evolving 
World of Science
1
We hope you enjoyed your adventures with Curiosity in 
Grade 6, and are now ready to continue our journey into the 
wonderful world of science. This again, is not just a textbook with 
facts?—?it is an invitation to question, to perform experiments, 
and to explore, as we try to understand the beautiful world we 
live in. The world of science covers everything?—?small and large, 
near and far. We may be looking at tiny cells inside a leaf, or 
the movement of the sun and the stars. We may be testing out 
the materials around us at home, or discussing how water ? ows 
underground. As you go through the chapters in this book, you 
will start new adventures that challenge your thinking, expand 
your knowledge, and help you become an explorer, making small 
discoveries for yourself. 
Before we dive into our exciting journey, take a moment to 
observe something special about this book. Look at the page 
numbers?—?they follow the playful ? ight of a butter? y and the 
soaring of a paper plane! Just as a butter? y ? utters freely and a 
paper plane ? ies into the sky, learning takes ? ight when curiosity 
leads the way. Did you know that something as simple as a paper 
plane inspired real scienti? c explorations of ? ight? From early 
inventors studying bird wings to modern engineers designing 
aircraft, the dream of ? ying started with simple observations and 
experiments. So, as you turn each page, let your imagination take 
? ight?—?exploring new ideas, discovering wonders, and reaching 
for the skies!
Chapter 1.indd   1 Chapter 1.indd   1 4/3/2025   4:50:06 PM 4/3/2025   4:50:06 PM
Curiosity | Textbook of Science | Grade 7
2
Exploration, of course, isn’t just about discovering new facts 
or learning about di? erent things in nature. Science, as we said 
in Grade 6, is a process, so it is about a way of thinking that 
welcomes curiosity, asks questions, and is open to the unknown. 
In Grade 7, we will try to ask deeper questions: How do things 
work? Why do events happen the way they do? And what can 
we learn from the patterns that we see in nature? 
To do this, we have to step out of this book, step out of the 
classroom perhaps, and experience the world through activities 
and experiments. These are experiences that we hope will not 
just be interesting or exciting but also serve as stepping stones 
to a deeper understanding of the environment we live in and of 
our place on this planet. We believe that this will also help you 
to see science as an ongoing process of discovery. And not just 
about discovery alone, but also about responsibility. As young 
science explorers, you will soon see how human activities are 
linked to what happens in the natural world and are connected 
to the society we live in. You will, we hope, also see the role that 
science can play in addressing environmental challenges and 
help in creating a more sustainable world. 
But let’s get back into this book for now. You will read about 
topics in di? erent ? elds of science, from physics and chemistry 
to biology and earth sciences. While they might appear as 
di? erent chapters, just as we had said in Grade 6, they are 
all interconnected. Scienti? c ideas in one area often inspire 
discoveries in another, or at least allow us to ask questions in 
another area. So, let’s take a quick journey through our book for 
this year. We will start by looking at the properties of materials 
around us, mostly the things we experience but perhaps never 
ask questions about?—?why are some fruits sour? What happens 
when we wash a haldi stain on our school uniform? 
Chapter 1.indd   2 Chapter 1.indd   2 4/3/2025   4:50:07 PM 4/3/2025   4:50:07 PM
The Ever-Evolving World of Science
3
We then move on and play with some 
electric batteries, lamps and wires to try to 
? nd other kinds of properties of materials. 
What kind of materials do we need to make a 
lamp glow? This will lead us to classifying 
materials based on their properties?—?and we 
will enter the world of metals and non-metals. 
We know from our experience that a torch 
battery runs out eventually, and can’t be used 
again. We’ll explore what kind of changes happen around us. 
Some changes can be reversed and others cannot be reversed. 
Batteries run out, ice melts into water, fruits ripen, rocks break 
into pebbles… what kind of changes are these? Some of these 
happen, or happen faster, when things are heated. We will look 
at how heat ? ows?—?whether it is the melting of an ice cube in a 
glass, or the melting of a glacier. Water is, of course, everywhere, 
and with the heat from the Sun, it evaporates from the seas and 
falls as rain, perhaps trickling down into the ground, somewhere 
far away.  
Chapter 1.indd   3 Chapter 1.indd   3 4/3/2025   4:50:09 PM 4/3/2025   4:50:09 PM
Page 4


The Ever-Evolving World of Science
The Ever-Evolving 
World of Science
1
We hope you enjoyed your adventures with Curiosity in 
Grade 6, and are now ready to continue our journey into the 
wonderful world of science. This again, is not just a textbook with 
facts?—?it is an invitation to question, to perform experiments, 
and to explore, as we try to understand the beautiful world we 
live in. The world of science covers everything?—?small and large, 
near and far. We may be looking at tiny cells inside a leaf, or 
the movement of the sun and the stars. We may be testing out 
the materials around us at home, or discussing how water ? ows 
underground. As you go through the chapters in this book, you 
will start new adventures that challenge your thinking, expand 
your knowledge, and help you become an explorer, making small 
discoveries for yourself. 
Before we dive into our exciting journey, take a moment to 
observe something special about this book. Look at the page 
numbers?—?they follow the playful ? ight of a butter? y and the 
soaring of a paper plane! Just as a butter? y ? utters freely and a 
paper plane ? ies into the sky, learning takes ? ight when curiosity 
leads the way. Did you know that something as simple as a paper 
plane inspired real scienti? c explorations of ? ight? From early 
inventors studying bird wings to modern engineers designing 
aircraft, the dream of ? ying started with simple observations and 
experiments. So, as you turn each page, let your imagination take 
? ight?—?exploring new ideas, discovering wonders, and reaching 
for the skies!
Chapter 1.indd   1 Chapter 1.indd   1 4/3/2025   4:50:06 PM 4/3/2025   4:50:06 PM
Curiosity | Textbook of Science | Grade 7
2
Exploration, of course, isn’t just about discovering new facts 
or learning about di? erent things in nature. Science, as we said 
in Grade 6, is a process, so it is about a way of thinking that 
welcomes curiosity, asks questions, and is open to the unknown. 
In Grade 7, we will try to ask deeper questions: How do things 
work? Why do events happen the way they do? And what can 
we learn from the patterns that we see in nature? 
To do this, we have to step out of this book, step out of the 
classroom perhaps, and experience the world through activities 
and experiments. These are experiences that we hope will not 
just be interesting or exciting but also serve as stepping stones 
to a deeper understanding of the environment we live in and of 
our place on this planet. We believe that this will also help you 
to see science as an ongoing process of discovery. And not just 
about discovery alone, but also about responsibility. As young 
science explorers, you will soon see how human activities are 
linked to what happens in the natural world and are connected 
to the society we live in. You will, we hope, also see the role that 
science can play in addressing environmental challenges and 
help in creating a more sustainable world. 
But let’s get back into this book for now. You will read about 
topics in di? erent ? elds of science, from physics and chemistry 
to biology and earth sciences. While they might appear as 
di? erent chapters, just as we had said in Grade 6, they are 
all interconnected. Scienti? c ideas in one area often inspire 
discoveries in another, or at least allow us to ask questions in 
another area. So, let’s take a quick journey through our book for 
this year. We will start by looking at the properties of materials 
around us, mostly the things we experience but perhaps never 
ask questions about?—?why are some fruits sour? What happens 
when we wash a haldi stain on our school uniform? 
Chapter 1.indd   2 Chapter 1.indd   2 4/3/2025   4:50:07 PM 4/3/2025   4:50:07 PM
The Ever-Evolving World of Science
3
We then move on and play with some 
electric batteries, lamps and wires to try to 
? nd other kinds of properties of materials. 
What kind of materials do we need to make a 
lamp glow? This will lead us to classifying 
materials based on their properties?—?and we 
will enter the world of metals and non-metals. 
We know from our experience that a torch 
battery runs out eventually, and can’t be used 
again. We’ll explore what kind of changes happen around us. 
Some changes can be reversed and others cannot be reversed. 
Batteries run out, ice melts into water, fruits ripen, rocks break 
into pebbles… what kind of changes are these? Some of these 
happen, or happen faster, when things are heated. We will look 
at how heat ? ows?—?whether it is the melting of an ice cube in a 
glass, or the melting of a glacier. Water is, of course, everywhere, 
and with the heat from the Sun, it evaporates from the seas and 
falls as rain, perhaps trickling down into the ground, somewhere 
far away.  
Chapter 1.indd   3 Chapter 1.indd   3 4/3/2025   4:50:09 PM 4/3/2025   4:50:09 PM
Curiosity | Textbook of Science | Grade 7
4
However, it isn’t just changes in materials 
around us that we see, or the hidden changes in 
water that we do not see. As we are growing, our 
bodies are changing as well. Especially around 
the middle-school years, our bodies are changing 
rapidly! Why? Not just us humans, there are 
life processes that are essential to all animals 
for their survival. To grow, we have to eat and 
breathe, blood has to circulate the nutrients 
from the food all over the body and so on. But 
why animals alone? Don’t plants also need food 
to grow? How do they get their food? Do they also 
breathe? How? Over the time that life has evolved 
on our planet Earth, it has ? gured out how to do this in a beautiful 
and carefully balanced way. Ah, but what is time? The clock on 
the wall or a wrist watch tells us the time and how it passes. We 
get prepared to go to school in the morning and are ready to sleep 
at night but have you thought about how we measure time? And 
how fast does something happen? 
Long before the age of electric clocks and digital watches, early 
humans observed the shadows of objects in the Sun and used the 
position of the shadows to tell the time. Light and shadows are 
not just useful for shadow 
puppets or to tell the time. 
Naturally, light helps us see 
and today, we’ve developed 
a lot of ways to generate 
light (so we can read a 
book at night, even when 
the Sun doesn’t shine). But, 
more importantly, asking 
questions about the nature 
Chapter 1.indd   4 Chapter 1.indd   4 4/3/2025   4:50:10 PM 4/3/2025   4:50:10 PM
Page 5


The Ever-Evolving World of Science
The Ever-Evolving 
World of Science
1
We hope you enjoyed your adventures with Curiosity in 
Grade 6, and are now ready to continue our journey into the 
wonderful world of science. This again, is not just a textbook with 
facts?—?it is an invitation to question, to perform experiments, 
and to explore, as we try to understand the beautiful world we 
live in. The world of science covers everything?—?small and large, 
near and far. We may be looking at tiny cells inside a leaf, or 
the movement of the sun and the stars. We may be testing out 
the materials around us at home, or discussing how water ? ows 
underground. As you go through the chapters in this book, you 
will start new adventures that challenge your thinking, expand 
your knowledge, and help you become an explorer, making small 
discoveries for yourself. 
Before we dive into our exciting journey, take a moment to 
observe something special about this book. Look at the page 
numbers?—?they follow the playful ? ight of a butter? y and the 
soaring of a paper plane! Just as a butter? y ? utters freely and a 
paper plane ? ies into the sky, learning takes ? ight when curiosity 
leads the way. Did you know that something as simple as a paper 
plane inspired real scienti? c explorations of ? ight? From early 
inventors studying bird wings to modern engineers designing 
aircraft, the dream of ? ying started with simple observations and 
experiments. So, as you turn each page, let your imagination take 
? ight?—?exploring new ideas, discovering wonders, and reaching 
for the skies!
Chapter 1.indd   1 Chapter 1.indd   1 4/3/2025   4:50:06 PM 4/3/2025   4:50:06 PM
Curiosity | Textbook of Science | Grade 7
2
Exploration, of course, isn’t just about discovering new facts 
or learning about di? erent things in nature. Science, as we said 
in Grade 6, is a process, so it is about a way of thinking that 
welcomes curiosity, asks questions, and is open to the unknown. 
In Grade 7, we will try to ask deeper questions: How do things 
work? Why do events happen the way they do? And what can 
we learn from the patterns that we see in nature? 
To do this, we have to step out of this book, step out of the 
classroom perhaps, and experience the world through activities 
and experiments. These are experiences that we hope will not 
just be interesting or exciting but also serve as stepping stones 
to a deeper understanding of the environment we live in and of 
our place on this planet. We believe that this will also help you 
to see science as an ongoing process of discovery. And not just 
about discovery alone, but also about responsibility. As young 
science explorers, you will soon see how human activities are 
linked to what happens in the natural world and are connected 
to the society we live in. You will, we hope, also see the role that 
science can play in addressing environmental challenges and 
help in creating a more sustainable world. 
But let’s get back into this book for now. You will read about 
topics in di? erent ? elds of science, from physics and chemistry 
to biology and earth sciences. While they might appear as 
di? erent chapters, just as we had said in Grade 6, they are 
all interconnected. Scienti? c ideas in one area often inspire 
discoveries in another, or at least allow us to ask questions in 
another area. So, let’s take a quick journey through our book for 
this year. We will start by looking at the properties of materials 
around us, mostly the things we experience but perhaps never 
ask questions about?—?why are some fruits sour? What happens 
when we wash a haldi stain on our school uniform? 
Chapter 1.indd   2 Chapter 1.indd   2 4/3/2025   4:50:07 PM 4/3/2025   4:50:07 PM
The Ever-Evolving World of Science
3
We then move on and play with some 
electric batteries, lamps and wires to try to 
? nd other kinds of properties of materials. 
What kind of materials do we need to make a 
lamp glow? This will lead us to classifying 
materials based on their properties?—?and we 
will enter the world of metals and non-metals. 
We know from our experience that a torch 
battery runs out eventually, and can’t be used 
again. We’ll explore what kind of changes happen around us. 
Some changes can be reversed and others cannot be reversed. 
Batteries run out, ice melts into water, fruits ripen, rocks break 
into pebbles… what kind of changes are these? Some of these 
happen, or happen faster, when things are heated. We will look 
at how heat ? ows?—?whether it is the melting of an ice cube in a 
glass, or the melting of a glacier. Water is, of course, everywhere, 
and with the heat from the Sun, it evaporates from the seas and 
falls as rain, perhaps trickling down into the ground, somewhere 
far away.  
Chapter 1.indd   3 Chapter 1.indd   3 4/3/2025   4:50:09 PM 4/3/2025   4:50:09 PM
Curiosity | Textbook of Science | Grade 7
4
However, it isn’t just changes in materials 
around us that we see, or the hidden changes in 
water that we do not see. As we are growing, our 
bodies are changing as well. Especially around 
the middle-school years, our bodies are changing 
rapidly! Why? Not just us humans, there are 
life processes that are essential to all animals 
for their survival. To grow, we have to eat and 
breathe, blood has to circulate the nutrients 
from the food all over the body and so on. But 
why animals alone? Don’t plants also need food 
to grow? How do they get their food? Do they also 
breathe? How? Over the time that life has evolved 
on our planet Earth, it has ? gured out how to do this in a beautiful 
and carefully balanced way. Ah, but what is time? The clock on 
the wall or a wrist watch tells us the time and how it passes. We 
get prepared to go to school in the morning and are ready to sleep 
at night but have you thought about how we measure time? And 
how fast does something happen? 
Long before the age of electric clocks and digital watches, early 
humans observed the shadows of objects in the Sun and used the 
position of the shadows to tell the time. Light and shadows are 
not just useful for shadow 
puppets or to tell the time. 
Naturally, light helps us see 
and today, we’ve developed 
a lot of ways to generate 
light (so we can read a 
book at night, even when 
the Sun doesn’t shine). But, 
more importantly, asking 
questions about the nature 
Chapter 1.indd   4 Chapter 1.indd   4 4/3/2025   4:50:10 PM 4/3/2025   4:50:10 PM
The Ever-Evolving World of Science
5
of light has given us a very deep understanding of the universe 
we live in. While we’ll perhaps learn about it only later , light and 
shadows are not just limited to things around us at home. 
Even the Earth and the Moon can cast shadows, leading to 
the fascinating phenomena of eclipses. And of course, we have 
day and night that depend on receiving light from the Sun. To 
understand all of this, we need to know how the Earth rotates 
around its axis, how the Moon goes around the Earth, and the 
Earth around the Sun. And the consequences of these movements 
on life on our beautiful planet. While all this might have your 
head spinning, think about it. Isn’t it amazing that we humans 
can wonder about the wonderful world we live in?
In the chapters that follow, you’ll 
also make simple observations and 
do fun experiments, and dive into 
topics that need careful thinking. 
Each chapter builds on what you 
already know and encourages you 
to ask questions, explore, do hands-
on experiments, and think like a 
scientist! As you will ? nd out, even 
those experiments that seem to 
con? rm what we think will happen, 
might lead to some additional 
questions that might need more 
experiments and more questions. 
1.1 Happy Exploring! 1.1 Happy Exploring! 1.1 Happy Exploring! 1.1 Happy Exploring! 1.1 Happy Exploring! 1.1 Happy Exploring! 1.1 Happy Exploring!
Activity 1.1: Question the Answer
In school or during tests, you’re usually given questions and 
expected to ? nd the answers. But let’s turn that around! To think 
Chapter 1.indd   5 Chapter 1.indd   5 4/3/2025   4:50:12 PM 4/3/2025   4:50:12 PM