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NCERT Class 9 Science Textbook Chapter 1 With Answer PDF Free Download
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 that 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 – everything is matter.
We can also see as we look around that all the things mentioned above occupy space and have mass. In other words, they have both mass* and volume**.
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.
1.1 Physical Nature of Matter
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?
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 the 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.
1.3 the States of Matter
Observe different types of matter around you. What are its different states? We can see that
matter around us exists in three different states– solid, liquid, and gas.
These states of matter arise due to the variation in the characteristics of the particles of matter. Now, let us study the properties of these three states of matter in detail.
1.3.3 The gaseous State
Have you ever observed a balloon seller filling a large number of balloons from a single cylinder of gas? Enquire from him how many balloons is he able to fill from one cylinder. Ask him which gas he has in the cylinder.
| Author | NCERT |
| Language | English |
| No. of Pages | 13 |
| PDF Size | 7.7 MB |
| Category | Science |
| Source/Credits | ncert.nic.in |
NCERT Solutions Class 9 Science Chapter 1 Matter in Our Surroundings
1. Which of the following are matter?
Chair, air, love, smell, hate, almonds, thought, cold, lemon water, the smell of perfume.
Solution:
The following substances are matter:
Chair
Air
Almonds
Lemon water
The smell of perfume (Smell is considered a matter due to the presence of some volatile substances in the air that occupy space & have mass.)
2. Give reasons for the following observation:
The smell of hot sizzling food reaches you several meters away, but to get the smell of cold
the food you have to go close.
Solution:
Particles in the air, if fueled with higher temperatures, acquire high kinetic energy which aids them
to move fast over a stretch. Hence the smell of hot sizzling food reaches a person even at a distance
of several meters.
3. A diver is able to cut through water in a swimming pool. Which property of matter does this observation show?
Solution:
The diver is able to easily cut through the water in the swimming pool because of the weak forces of
attraction between water molecules. It is this property of water that attributes to easy diving.
4. What are the characteristics of the particles of matter?
Solution:
The characteristics of particles of matter are:
(a) Presence of intermolecular spaces between particles
(b) Particles are in constant motion
(c) They attract each other
(d) All matter is composed of very small particles which can exist independently.
Exercise-1.5 Page:10
1. Why does a desert cooler cool better on a hot dry day?
Solution:
It is because the temperature is high and it is less humid on a hot dry day which enables better evaporation. High levels of this evaporation provide better cooling effects.
2. How does the water kept in an earthen pot (matka) become cool during summer?
Solution:
An earthen pot is porous in nature. These tiny pores facilitate penetration of water and hence their evaporation from the pot surface. The process of evaporation requires energy which is contributed by water in the pot as a result of which water turns cooler.
3. Why does our palm feel cold when we put on some acetone or petrol or perfume on it?
Solution:
Acetone, petrol, and perfume are volatile substances that get evaporated when they come in contact
with air. Evaporation is facilitated as it uses energy from the palm hence leaving a cooling effect on our
palms.
4. Why are we able to sip hot tea or milk faster from a saucer rather than a cup?
Solution:
A saucer has a larger surface area than a cup which promotes quicker evaporation hence the tea or milk in a saucer cools down faster.
5. What type of clothes should we wear in summer?
Solution:
In summer, it is preferred to wear light-colored cotton clothes because light color reflects heat, and cotton materials have pores that absorb sweat, facilitating their evaporation hence causing a cooling effect on the skin.
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