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CNMS ICSE - 7 Std
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Chapter: 01. Matter And Its Composition

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SECTION A: Multiple Choice Questions (MCQs)

(b) Maharishi Kanad
(b) Adhesive force
(​c​) Brownian motion
(​c​) Naphthalene
(​c​) Gas
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SECTION B: Fill in the Blanks

volume
10²¹ (or 10^21)
cohesive
fluids
deposition
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SECTION C: True or False Questions

True (Mass is the quantity of matter and remains constant, whereas weight is the gravitational force and changes.)
False (Atoms usually do not have an independent existence; they join to form molecules.)
False (Kinetic energy increases with an increase in temperature, leading to faster movement.)
True (Solids are tightly packed, resulting in negligible space and strong forces.)
False (Oil and diesel are insoluble/immiscible in water.)
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SECTION D: Explanations of Terms

Matter: Anything that has mass, occupies space, and can be perceived by our senses.
Brownian motion: The continuous, random zigzag motion of the particles of matter.
Interconversion of states of matter: The process by which matter changes from one state to another and back to its original state without any change in its chemical composition.
Sublimation: The process in which a solid changes directly into a gas on heating, without passing through the liquid state.
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SECTION E: Differentiate the Concepts

Mass and Weight:
Mass is the quantity of matter contained in an object and remains the same at all places.
Weight is the force with which the Earth attracts an object towards itself and changes from place to place.
Cohesive force and Adhesive force:
Cohesive force is the force of attraction acting between particles of the same kind.
Adhesive force is the force of attraction acting between particles of different kinds.
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SECTION F: Diagram-Based Questions

Solid state. The intermolecular force of attraction is strongest here because the molecules are very closely packed together, leaving negligible intermolecular space.
Gas state. The molecules are far apart, meaning the intermolecular space is very large.
In a solid, the position of the molecules is fixed. They are not free to move around and can only vibrate about their mean positions.
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SECTION G: Short Answer Questions

When the temperature is increased, the movement of the particles increases. This is because particles gain kinetic energy as temperature rises.
It is difficult to swim in fast-flowing water because water offers resistance. This demonstrates the property of matter that it offers resistance to any force applied to it.
An atom is the smallest particle of matter that exhibits all properties of matter but usually does not have an independent existence. A molecule is made of two or more atoms and does have an independent existence.
Gas molecules occupy all available space because their intermolecular spaces are very large and the intermolecular force of attraction is very weak or negligible, allowing them to move freely in all directions.
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SECTION H: Long Answer Questions

Experiment to show particles have spaces between them:
Method: Fill a beaker with some water and mark the initial water level. Add a teaspoon of sugar and observe the level rise. Stir the sugar well with a glass rod until it dissolves completely, then observe the water level again.
Observation: The water level initially rises when sugar is added, but once the sugar is completely dissolved, the water level recedes back to the initial marked level.
Discussion: This happens because sugar particles break down into extremely small particles. These tiny sugar particles get accommodated in the empty spaces (interparticle space) present between the water molecules, proving that particles of matter have spaces between them.
Comparison Table:
Parameter
Solid
Liquid
Gas
Shape
Definite shape
No definite shape; takes the shape of the container
No definite shape
Volume
Definite volume
Definite volume
No definite volume; occupies all available space
Compressibility
Incompressible
Slightly compressible
Highly compressible
Fluidity
Does not flow
Flows from a higher level to a lower level
Flows in all directions
Position of molecules
Fixed; they only vibrate about their mean positions
Not fixed; free to move within the boundary of the liquid
Not fixed; free to move in all directions
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SECTION I: Observation-Based / Everyday Use Questions

The process responsible is condensation. The air surrounding the cold bottle contains water vapour (gas). When this water vapour comes in contact with the cold surface of the bottle, it loses heat energy, cools down, and changes state from gaseous vapour to liquid water droplets.
LPG is stored under very high pressure in cylinders, which forces the gas molecules close together, changing them into a liquid state. When the regulator valve is opened, the pressure is released. The decrease in pressure allows the molecules to move far apart, transforming the liquid back into its gaseous state.
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