Hello my dear students! Welcome to your Science class. I am so happy to see you all today. Today we begin a brand new chapter, Chapter 1, and it is called "Exploring the Investigative World of Science." Now before we start, I want you to think about something. Have you ever looked at something very ordinary in your daily life and suddenly wondered why it happens that way? Maybe while eating your mother's delicious cooking, or playing outside, or even while just sitting in your classroom. That wondering, that curiosity, is exactly where science begins. And in this chapter, we are going to learn how to turn that curiosity into something powerful — into investigation, into discovery, into real science.
So let's begin, shall we?
Now students, I want you to look at the first page of your chapter. You will see some questions there. These are not questions for your exams, so don't worry! They are there just to make you think, to spark that curiosity in you. One question asks, "Why is one side of a puri thinner than the other?" Now isn't that interesting? We have all eaten puris at home, haven't we? We know that when a puri is fried in hot oil, it puffs up beautifully, and one side is nice and thin and crispy while the other side is slightly thicker. Have you ever wondered why that happens? This is exactly the kind of question that a scientist would ask. And today, we are going to learn how to investigate such questions properly.
But first, let me tell you something about what we have been doing in our science journey so far. If you remember, in Grade 6, we discovered how science begins with wonder. We asked simple "Why?" and "How?" questions about the world around us. Remember? We looked at different plants and animals, observed the shapes of leaves, the different kinds of insects, and we wondered — why has nature created so much variety? That was our first step into the world of science.
Then in Grade 7, we learnt something very important. We learnt that science is always evolving. That means when we find an answer to a question, that answer often opens up new questions. Our ideas slowly change as we explore deeper into any topic. This is what makes science so exciting — it is never finished, it is always growing!
Now in Grade 8, we take the next big step. We enter what is called the Investigative World of Science. Here, wonder and evolution come together to form the heart of how science actually works. We don't just want you to learn new facts anymore — though you will learn many! We want you to learn how to find new facts. Investigation in science means more than just looking at something and asking simple questions. Now you can ask more focused questions, and design ways to do simple experiments to answer those questions. Then you use your observations to improve your understanding. This is what scientists do, and today, my dear students, you are going to learn to do this too!
So let's understand this step by step. First, we learn how to use questions as starting points. Then we try to observe carefully. Then we experiment thoughtfully. And finally, we explain clearly what we see. When we do all this, each of you becomes not just a learner but also an investigator — a young scientist exploring real-world puzzles. And these puzzles can range from everyday life, like why does dough rise, to bigger mysteries like is the world getting warmer?
Now students, I want you to notice something special about this book. As you turn each page, you will notice the interesting design of our page numbers. On the left-hand pages, at the bottom, you will find the image of a root. This root symbolises the deep, solid foundation of knowledge that keeps us connected to our environment, our traditions, and our cultural and natural heritage. On the right-hand pages, in the top corner, you will find a kite soaring in the sky. This reminds us that curiosity must take flight if we are to explore the unknown. Together, these two symbols — the root and the kite — invite you to stay grounded in real observations while allowing your ideas to soar towards new horizons. Remember, investigation in science works best only when we balance the solid ground of careful observation with the freedom of creative thinking. This is such a beautiful message, isn't it? Stay rooted, but dream big!
Now let's talk about what we will be learning this year. Our investigative adventure will take us on a journey from the tiny microbes we cannot see to planet-wide challenges we cannot ignore.
We will start by examining something as small as a single drop of water, and uncover a hidden world of tiny organisms — unseen but deeply linked to us. Some of these tiny organisms are invisible helpers that help us digest our food or produce medicines, while others can be harmful, causing infections. Then we will ask — what does our body need to stay healthy? How do we fight these infections? We will find out how nutritious food, exercise, medicines, and vaccines help us stay healthy and fight infections.
But that's just the beginning. In today's world, science plays a major role in improving our lives. For example, we use electric current in many ways to help make our lives easier. We depend on the heating effect of electric current to keep us warm, while the magnetic effect helps motors run and machines function. These phenomena depend on fundamental forces. So after watching electricity do work, we move on to study these forces themselves — forces that make objects speed up, slow down, or change direction. Understanding forces helps explain why a ball thrown up in the air falls back to the ground, or why a car stops when the brakes are applied.
This also leads us to the idea of pressure — how the force is distributed over an object. The same concepts of force and pressure also decide how air moves. A small difference in pressure can result in a gentle breeze, while a stronger pressure difference can lead to strong winds, and sometimes even cyclones. So these forces are connected to powerful weather events — storms and cyclones — that affect our daily lives, agriculture, and even our safety.
To truly understand how air can exert pressure or why water boils at a certain temperature, we need to zoom into these materials and see what kind of particles they are made of, and how they move around. Everything around us is made of tiny particles. In materials that are solid, these particles cannot move much, while in gases, they can move around freely. Classifying things around us is an important feature of science. We can also classify materials around us into elements, which are pure substances, compounds, which are two or more elements bonded together, and mixtures, which are combinations that can be separated physically. Once we know how particles combine or mix, we can then understand solutions — for example, how sugar dissolves in tea to make it sweet.
From the world of particles and mixtures, we then move into the world of light. We will study how light rays reflect off flat and curved mirrors, and bend when passing through lenses. This helps us understand the working of many objects around us. The bending of light explains what happens when we see an image in a shiny metal spoon or how corrective glasses help many of us see clearly. It's not just a polished mirror that reflects light — rough surfaces reflect light as well, and so does the Moon. Depending on the relative positions of the Earth, Moon, and Sun, a slightly different part of the Moon is illuminated each night, giving rise to the beautiful phases of the Moon that we see in the sky. Watching the periodic cycles of the Moon's phases allowed humans to come up with the first calendars. By combining careful observations of sunrises, sunsets, and lunar cycles, various calendars came into being. Isn't it fascinating that the calendars which determine our routines on Earth are linked to the motions of objects far beyond our planet?
But it's not just calendars or the movements of the Sun and Moon that are linked. Right here on Earth, there are marvellous and complex patterns of relationships between living organisms and their environments. Every living being — from the tiniest insect to the largest whale, from blades of grass to tall trees — depends on and responds to the air, water, sunlight, and other organisms around them, forming the ecosystems that support life on our planet.
In the final chapter of this book, we can put it all together and try to understand what makes Earth "just right" for life and to recognise the urgent challenges that our planet now faces. Most importantly, the Earth lies at the perfect distance from the Sun, where water remains liquid, and it has an atmosphere that provides the oxygen we breathe while shielding us from harmful ultraviolet rays. But human activities on the planet can cause small changes in the temperature of the Earth, disrupting climate patterns, with dangerous consequences. At the heart of both the problem and any possible solution is us. We are the ones influencing Earth's climate. But we are also the ones who can — and must — use science to understand these changes and guide our actions.
The same scientific principles that we have guided our journey through the middle stages — observing, measuring, experimenting — will be key in helping us protect the delicate balance on which life depends. The challenges ahead won't always be easy. I hope some of you will try to solve these difficult problems with curiosity as your guide.
Now, my dear students, let us go back to that question we started with: Why is one side of a puri thinner than the other? I want you to understand that science is everywhere! You don't need a fancy laboratory to do simple experiments. Even your kitchen at home is a wonderful place to observe and ask questions. All you need is to start with curiosity, careful observation, and asking "What happens if...?"
Have you noticed how a puri or a batura puffs up when placed in hot oil? Or how a phulka swells when put directly on the flame? Why does it puff up like a balloon? And why is one side thinner than the other? These are questions a scientist might ask — and you can too! Let's see how we can investigate this simple everyday phenomenon like a scientist would.
First, we will try to ask a scientific question. What are the different things that may change the way a puri puffs up when fried? To answer this, we may want to do some simple experiments. For that, we try to find out two main things — what all can we change or control when we do the experiment, and what all can we observe to see if these changes made any difference.
In this case, we can perhaps think of changing the thickness and the size of the rolled dough. We could also try to use different types of flour — atta, maida, and so on. While frying the puri, we can also change the temperature of the hot oil, or try and drop the rolled dough into the oil in different ways. Do we drop it vertically? Do we slide it at an angle? Do we slide it slowly? Notice that these are things that we can control — we call these variables.
However, to make sense of the changes, we also need to think of what we can observe or measure. Some of these may have just yes or no answers, and in some cases there might be a number we can measure. Maybe we can start by checking whether the puri puffs up — that is a yes or no answer. Or we can measure the time it takes to puff up — that would be in seconds. We can check whether a very thick layer of dough still gives a thin side to the puri. Further, while doing such experiments, it is better to change only one thing at a time while keeping the other conditions the same. This is very important, students! For example, if we wanted to see the effect of boiling hot, hot, and not very hot oil, we would use circles of dough of the same thickness, and drop them in the same way. It is also a good idea to keep notes of everything that you see and sense when doing an experiment. Did the oil splatter, smell, or smoke? And after doing one round of experiments, you may think of more questions. Do puris puff better when made fresh or from stored dough? What happens if I prick a hole in the puri before frying?
This is exactly how all scientific experiments, from simple to the most complicated, are done. This is the idea of systematic investigation. And just so you know, even this simple everyday observation — of a puri puffing — is not really completely understood by scientists today! There is still so much to learn, and maybe one day, one of you will discover the full explanation!
So students, whether it is the puffing of a puri or the shrinking bright part of the Moon after purnima, let your careful observations guide you along your explorations into the investigative world of science.
Now, let me also talk about the "Probe and Ponder" questions on the first page. There is a question that asks: "Are there more grains of sand on all the beaches and deserts of the world, or more stars in our galaxy?" This is a wonderful question to think about, isn't it? Can you imagine how many grains of sand there are on all the beaches and deserts? And how many stars are there in our galaxy, the Milky Way? Scientists have actually tried to estimate both numbers. The number of stars in our galaxy is estimated to be about 100 to 400 billion stars. And the number of grains of sand on all Earth's beaches and deserts is estimated to be roughly 7.5 quintillion grains, which is 7.5 followed by 18 zeros! That is an enormous number! So actually, there are more grains of sand on Earth than there are stars visible in the night sky. But remember, this is just an estimate, and both numbers are so huge that it is hard to really comprehend them!
There is also another question: "Right from Grade 6, we've observed the incredible diversity of plants and animals around us. From the different shapes of leaves to the many kinds of insects — why has nature created such a vast variety?" This is another great question for investigation. Scientists believe that this variety, what we call biodiversity, exists because different organisms have adapted to different environments over millions of years. Each species has evolved special characteristics that help it survive in its particular habitat. This diversity makes our planet resilient and beautiful.
Now, students, I want you to think about your own question. Is there such a question that makes you curious about the world? The chapter asks you to write it down. Take a moment to think about something you have always wondered about. Maybe it is about the food you eat, the weather, the plants in your garden, or the animals you see around you. Write that question down and keep it safe. This is the beginning of your own scientific investigation!
Now let me recap what we have learned in this chapter so that it stays in your mind clearly.
First, we learned that science begins with curiosity — asking "Why?" and "How?" about the world around us. Second, we learned that science is always evolving — answers lead to new questions, and our ideas change as we explore deeper. Third, we learned that investigation in science means asking focused questions, designing experiments, making careful observations, and explaining what we see. Fourth, we learned that we don't need fancy labs — our everyday surroundings, like our kitchen, are great places to investigate. Fifth, we learned about systematic investigation — controlling variables, changing one thing at a time, and keeping good notes. And finally, we learned that even simple everyday phenomena, like a puri puffing up, can be subjects of scientific investigation, and there is still so much for scientists to discover!
This chapter sets the stage for everything we will learn this year. We will explore the tiny world of microbes, learn about health and diseases, understand electricity and forces, study light and its properties, learn about the Moon's phases, and finally understand how Earth is our home and how we can protect it. All of this will be done using the investigative approach we have learned today — observing carefully, questioning, experimenting, and explaining.
So my dear students, I hope you are as excited as I am! Science is all around us, and now you have the tools to explore it like a true scientist. Keep that curiosity alive, keep asking questions, and never stop wondering about the amazing world we live in.
Happy investigating, students! See you in the next class!