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Textbook for Class IX, e=mc, SCIENCE, Hydrogen, Carbon, Oxygen, Phosphorus, Sulphur, Iron, Copper, Lead, S, Silver, Gold, OP, Platina, Mercury

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CONTENTS, FOREWORD, ii, Chapter 1, MATTER IN OUR SURROUNDINGS, 1, Chapter 2, Is MATTER AROUND Us PURE, 14, Chapter 3, ATOMS AND MOLECULES, 31, Chapter 4, STRUCTURE OF THE ATOM, 46, Chapter 5, THE FUNDAMENTAL UNIT OF LIFE, 57, Chapter 6, TISSUES, 68, Chapter 7, DIVERSITY IN LIVING ORGANISMS, 80, Chapter 8, MOTION, 98, Chapter 9, FORCE AND LAWS OF MOTION, 114, Chapter 10 GRAVITATION, 131, Chapter 11, WORK AND ENERGY, 146, Chapter 12, SOUND, 160, Chapter 13, WHY DO WE FALL ILL, 176, Chapter 14, NATURAL RESOURCES, 189, Chapter 15, IMPROVEMENT IN FOOD RESOURCES, 203, ANSWERS, 216 - 218

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Chapter 1, MATTER IN OUR SURROUNDINGS, As we look at our surroundings, we see a large, variety of things with different shapes, sizes, and textures. Everything in this universe is, made up of material which scientists have, named “matter". The air we breathe, the food, we eat, stones, clouds, stars, plants and, animals, even a small drop of water or a, particle of sand- each thing is matter. We can, also see as we look around that all the things, mentioned above occupy space, that is,, volume* and have mass., Activity, 1.1, Take a 100 mL beaker., Fill half the beaker with water and, mark the level of water., Dissolve some salt/ sugar with the help, of a glass rod., Observe any change in water level., What do you think has happened to, the salt?, Where does it disappear?, Does the level of water change?, Since early times, human beings have, been trying to understand their surroundings., Early Indian philosophers classified matter in, the form of five basic elements - the, "Panch Tatva"- air, earth, fire, sky and water., According to them everything, living or non-, living, was made up of these five basic, elements. Ancient Greek philosophers had, In order to answer these questions we, need to use the idea that matter is made up, of particles. What was there in the spoon, salt, or sugar, has now spread throughout water., This is illustrated in Fig. 1.1., arrived at a similar classification of matter., Modern day scientists have evolved two, types of classification of matter based on their, physical properties and chemical nature., In this chapter we shall learn about, matter based on its physical properties., Chemical aspects of matter will be taken up, in subsequent chapters., Water, Water, Water, Add salt, Ştir, Salt, Particles of water, Salt, magnified millions, of times, Fig. 1.1: When we dissolve salt in water, the particles, 1.1 Physical Nature of Matter, of salt get into the spaces between particles, of water., 1.1.1 MATTER IS MADE UP OF PARTICLES, For a long time, two schools of thought, prevailed regarding the nature of matter. One, school believed matter to be continuous like, 1.1.2 How SMALL ARE THESE PARTICLES, OF MATTER?, a block of wood, whereas, the other thought, that matter was made up of particles like, sand. Let us perform an activity to decide, about the nature of matter – is it continuous, Activity, 1.2, Take 2-3 crystals of potassium, permanganate and dissolve them in, 100 mL of water., or particulate?, * The SI unit of volume is cubic metre (m). The common unit of measuring volume is, litre (L) such that 1L = 1 dm2, 1L = 1000 mL, 1 mL = 1 cm.

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Take out approximately 10 mL of this, solution and put it into 90 mL of clear, 1.2.2 PARTICLES, OF, МАТTER, ARE, water., CONTINUOUSLY MOVING, Take out 10 mL of this solution and, put it into another 90 mL of clear water., Keep diluting the solution like this 5 to, Activity, 1.3, 8 times., Is the water still coloured ?, Put an unlit incense stick in a corner, of your class. How close do you have to, go near it so as to get its smell?, Now light the incense stick. What, happens? Do you get the smell sitting, at a distance?, n10 mL, 10 mL, A10 mL, Record your observations., 100 mL, l100 mL, 100 mL, 100 mL, 100 mL, Activity, 1.4, Fig. 1.2: Estimating how small are the particles of, matter. With every dilution, though the colour, becomes light, it is still visible., Take two glasses/beakers filled with, water., Put a drop of blue or red ink slowly, and carefully along the sides of the first, beaker and honey in the same way in, This experiment shows that just a few, crystals of potassium permanganate ca, colour a large volume of water (about, 1000 L). So we conclude that there must be, millions of tiny particles in just one crystal, of potassium permanganate, which keep o, dividing themselves into smaller and smaller, particles. Ultimately a stage is reached when, the particles cannot divide further into, smaller particles., The same activity can be done using, 2 mL of Dettol instead of potassium, permanganate. The smell can be detected, even on repeated dilution., the second beaker., Leave them undisturbed in your house, or in a corner in the class., Record your observations., What do you observe immediately after, adding the ink drop?, What do you observe immediately after, adding a drop of honey?, How many hours or days does it take, for the colour of ink to spread evenly, throughout the water?, Activity, 1.5, The particles of matter are very small –, they are small beyond our imagination!!!!, Drop a crystal of copper sulphate or, potassium permanganate into a glass, of hot water and another containing, 1.2 Characteristics of Particles of, Matter, cold water. Do not stir the solution., Allow the crystals to settle at the, 1.2.1 PARTICLES OF MATTER HAVE SPACE, bottom., What do you observe just above the, solid crystal in the glass?, What happens as time passes?, What does this suggest about the, particles of solid and liquid?, Does the rate of mixing change with, temperature? Why and how?, BETWEEN THEM, In activities 1.1 and 1.2 we saw that particles, of sugar, salt, Dettol, or potassium, permanganate got evenly distributed in water., Similarly, when we make tea, coffee or, lemonade (nimbu paani ), particles of one type, of matter get into the spaces between particles, of the other. This shows that there is enough, space between particles of matter., From the above three activities (1.3, 1.4 and, 1.5), we can conclude the following:, SCIENCE

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If we consider each student as a particle, of matter, then in which group the, Particles of matter are continuously, moving, that is, they possess what we call, the kinetic energy. As the temperature rises,, particles move faster. So, we can say that with, increase in temperature the kinetic energy of, the particles also increases., In the above three activities we observe, that particles of matter intermix on their own, with each other. They do so by getting into, the spaces between the particles. This, intermixing of particles of two different types, of matter on their own is called diffusion. We, also observe that on heating, diffusion, becomes faster. Why does this happen?, particles held each other with the, maximum force?, Activity, 1.7, Take an iron nail, a piece of chalk and, a rubber band., Try breaking them by hammering,, cutting or stretching., In which of the above three substances, do you think the particles are held, together with greater force?, Activity, 1.8, 1.2.3 PARTICLES OF MATTER ATTRACT, Open a water tap, try breaking the, stream of water with your fingers., Were you able to cut the stream of, EACH OTHER, Activity, 1.6, water?, What could be the reason behind the, Play this game in the field- make four, groups and form human chains as, suggested:, The first group should hold each other, from the back and lock arms like Bihu, stream of water remaining together?, The above three activities (1.6, 1.7 and, 1.8) suggest that particles of matter have force, acting between them. This force keeps the, dancers (Fig. 1.3)., particles together. The strength of this force, of attraction varies from one kind of matter, to another., uestions, 1., Which of the following are, matter?, Chair, air, love, smell, hate,, almonds, thought, cold, cold-, drink, smell of perfume., 2. Give reasons for the following, Fig. 1.3, observation:, The smell of hot sizzling food, reaches you several metres, away, but to get the smell from, cold food you have to go close., 3. A diver is able to cut through, water in a suwimming pool. Which, property of matter does this, The second group should hold hands, to form a human chain., The third group should form a chain, by touching each other with only their, finger tips., Now, the fourth group of students, should run around and try to break the, three human chains one by one into, as many small groups as possible., Which group was the easiest to break?, Why?, observation show?, 4. What are the characteristics of, the particles of matter?, MATTER IN OUR SURROUNDINGS, 3