NCERT Book Class 9 Science Matter In Our Surroundings

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.

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 nonliving, was made up of these five basic elements. Ancient Greek philosophers had 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.

1.1 Physical Nature of Matter

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 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 or particulate?

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?

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.

1.2 Characteristics of Particles of Matter

1.2.1 PARTICLES OF MATTER HAVE SPACE 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.

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