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

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SECTION 1: ACTIVITY-BASED QUESTIONS

Activity 1 Experiential Learning (MEP QUEBELINES)

Question: What are the two common properties of matter shown in this experiment?
Answer:
Matter occupies space: This is shown when the marbles are added to the glass tumbler and the water level rises to accommodate them.
Matter has mass: This is shown by the increase in the overall weight of the glass tumbler after the marbles are added.

Activity ② Experiential Learning (INEP GUIDELINES)

Question: What is the impact of temperature on the movement of particles?
Answer: Temperature directly affects the kinetic energy of the particles. An increase in temperature increases the kinetic energy of the particles, causing them to move faster. A decrease in temperature decreases their kinetic energy, slowing down their movement.

Activity ③ Experiential Learning (INEP GUIDELINES)

Question: What is the space between particles of matter known as?
Answer: The space between the particles of matter is known as the interparticle or intermolecular space.

Activity 4: Experiential Learning (NEP GUIDELINES)

Question: Why does intermolecular force of attraction vary in different substances?
Answer: The intermolecular force of attraction depends on the intermolecular space. In substances where molecules are very close (having less intermolecular space), the force of attraction is stronger. In substances where the molecules are far apart (having larger intermolecular space), the force of attraction is weaker.

Activity 5 Experimental Learning (INEP GUIDELINES)

Question: Why does the fragrance of incense stick fill the other jar?
Answer: The fragrance fills the other jar because the smoke particles (gas) are in continuous random motion, have negligible intermolecular force of attraction, and have very large intermolecular spaces. This allows them to diffuse quickly and move in all directions to occupy all the available space.
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SECTION 2: EXERCISES FOR REVISION

Page 8-9: Exercise for Revision

A. Tick (✓) the correct options.
Which of the following is/are property (ies) of matter?
Answer: (d) All of these
The smallest particle that exhibits all the properties of matter and does not have an independent existence is called a/an ___________.
Answer: (a) atom
The smallest particle of matter that exhibits all the properties of matter and have an independent existence is called ___________.
Answer: (b) molecule
The continuous zigzag motion of the particles of matter is called the
Answer: (a) Brownian motion
The force of attraction between the same kind of particles is called __________ force.
Answer: (a) cohesive
When the molecules in matter are very close, there is __________ intermolecular space and __________ intermolecular force of attraction.
Answer: (d) less, stronger
B. Assertion-Reason based Question.
Question:
Assertion (A): The intermolecular force of attraction varies in different substances.
Reason ®: The intermolecular force of attraction depends upon intermolecular space.
Answer: (a) Both A and R are true and R is the correct explanation of the assertion.

Page 12-13: Exercise for Revision

A. Tick (✓) the correct options.
Which of the following is not a property of a solid?
Answer: (d) Intermolecular force of attraction is weak.
Which of the following is incorrect about gases?
Answer: (​c​) Their molecules are not free to move, they only vibrate about their mean positions.
Which of the following cannot flow?
Answer: (​c​) ice
Ram takes out a bottle of cold water from the fridge. He wipes the bottle dry and leaves it on the table. A few minutes later, he finds water droplets on the outer surface of the bottle. Which one of the following processes leads to the formation of droplets on the surface of the bottle?
Answer: (​c​) condensation
B. Assertion-Reason based Questions.
Question:
Assertion (A): Applying pressure can change a liquid into gas.
Reason ®: When pressure is applied, molecules move closer to each other and intermolecular force increases.
Answer: (d) A is false but R is true. (Applying pressure changes a gas into a liquid, not a liquid into a gas. The reason is scientifically true as pressure forces molecules together).
Question:
Assertion (A): Condensation is a cooling process.
Reason ®: During condensation, molecules lose energy.
Answer: (d) A is false but R is true. (Condensation is scientifically a warming process because it releases heat energy to the surroundings. However, the reason is true because gas molecules lose kinetic energy as they transition into a liquid).
Complete the flowchart for Revision
Question: Complete the blanks in the flowchart.
Answer:
Matter: Anything that has mass, occupies space, and is made up of particles.
Particles: Divided into:
No independent existence: Atom
Has independent existence: Molecule
States of Matter:
Definite shape and definite volume: Solid
Definite volume but no definite shape: Liquid
No definite volume or shape: Gas
Interconversion of States: Carried out by changing:
Temperature
Pressure
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SECTION 3: CHAPTER END EXERCISES (NEP Guidelines)

A. Short Answer Questions

Question: Define matter. List two properties of matter.
Answer: Matter is defined as anything that has mass and occupies space. Two common properties of matter are:
It has mass.
It occupies space.
Question: What is interconversion of states of matter?
Answer: The process by which matter changes from one state to another and back to its original state, without any change in its chemical composition, is called interconversion of states of matter.
Question: Why do liquids and gases flow, whereas solids do not?
Answer: Liquids and gases have larger intermolecular spaces and weaker intermolecular forces of attraction, allowing their molecules to move freely and flow. In solids, the intermolecular spaces are negligible and the intermolecular forces of attraction are very strong, keeping the molecules tightly locked in fixed positions.
Question: Why does matter exist in different states?
Answer: Matter exists in different states due to differences in key physical parameters of its particles:
The size of intermolecular spaces.
The strength of intermolecular forces of attraction.
The movement/kinetic energy of the molecules.

B. Long Answer Questions

Question: What are the characteristics of particles of matter? Explain.
Answer:
Extremely small size: Particles of matter are so small they cannot be seen with the naked eye or ordinary microscopes (e.g., a drop of water contains about
math
⁠
molecules).
Continuous random motion: Particles are always moving in a continuous zigzag path, called Brownian motion, because they possess kinetic energy.
Intermolecular spaces: There are spaces between particles, known as intermolecular or interparticle spaces.
Intermolecular force of attraction: A force exists between the particles that holds them together. It can be cohesive (between same kind of particles) or adhesive (between different kinds of particles).
Question: Differentiate between solids, liquids and gases on the basis of their intermolecular space, intermolecular force of attraction, shape, volume and arrangement of molecules.
Answer:
Parameter
Solid
Liquid
Gas
Intermolecular Space
Almost negligible
Larger than solids
Very large
Intermolecular Force
Very strong
Weak
Weakest / Negligible
Shape
Definite shape
No definite shape (takes container’s shape)
No definite shape
Volume
Definite volume
Definite volume
No definite volume (occupies all available space)
Arrangement of Molecules
Very closely packed
Loosely packed
Far apart
⁠
Question: How do different states of water interconvert on heating and cooling? Explain briefly.
Answer: Water changes states when temperature is altered:
On Heating:
Melting: Solid ice (at
math
⁠
) absorbs heat and melts into liquid water.
Boiling: Further heating of liquid water (to
math
⁠
) turns it into gaseous steam/water vapour.
On Cooling:
Condensation: Gaseous steam cools down, losing energy to convert back into liquid water.
Freezing: Liquid water cooled in a freezer (to
math
⁠
) freezes back into solid ice.
Question: Observe Fig. A carefully. Now, explain how heat helps change the states of matter.
Answer: Heat energy is absorbed by the particles of matter, increasing their kinetic energy. As temperature rises from
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⁠
to
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⁠
, the particles begin to move and vibrate more rapidly. This increased motion allows the particles to overcome the intermolecular force of attraction keeping them together. The intermolecular spaces widen, causing the solid to melt into a liquid, and eventually boil into a gas.
Question: How does pressure help in interconversion of gases to liquids and liquids to gases? Give example.
Answer:
Gases to Liquids: Applying high pressure compresses gas particles, forcing them closer together. This reduces intermolecular space and increases intermolecular forces, turning the gas into a liquid. Example: Liquefied Petroleum Gas (LPG) is stored in cylinders as a liquid under high pressure.
Liquids to Gases: When the applied pressure is released, the molecules gain space to move apart, weakening the intermolecular force and changing the substance back into a gas. Example: When the regulator valve of an LPG cylinder is opened, the pressure is released, and the liquid turns back into cooking gas.
Question: Observe Fig. B (i) and (ii) and answer the following questions:
(a) Which cloth is heavier and why?
Answer: The wet cloth in Fig. B (ii) is heavier. This is because it contains both the mass of the dry cloth and the mass of the liquid water absorbed into its fibers.
(b) Write two properties of matter that is depicted in picture (ii) only.
Answer:
Matter has mass: Water adds measurable weight to the cloth.
Matter occupies space: Water molecules occupy the air/intermolecular spaces inside the pores of the cloth.

C. Application/Skill-based Questions

Question: Akshita takes a bottle and puts a funnel in its mouth. She seals the space between the funnel and the bottle tightly with the help of playdough and pours water into the funnel. What does she observe after pouring water? Does the water enter the bottle? What can we conclude from this activity?
Answer:
Observation: The water remains trapped in the funnel and does not enter the bottle (or only a tiny bit trickles down and then stops completely).
Reason: The bottle is already full of air. Since the funnel’s joint is sealed air-tight with playdough, the air inside has no pathway to escape and make room for the incoming water.
Conclusion: This activity concludes that air (gas) occupies space and offers resistance.
Question: When your mother cooks food, you smell the food across the house. Why does this happen?
Answer: This happens due to diffusion. The hot vapor particles rising from the food carry its aroma. These gas particles have high kinetic energy and move very fast. They rapidly mix with and spread through the air particles of the room, traveling across the house.
Question: Observe Fig. C and answer the following questions:
(a) Why does the shape of a balloon change when air is released from it?
Answer: The shape of the balloon shrinks because the pressurized air inside is released. Since air is the matter occupying space inside the balloon, its exit removes the volume pushing against the balloon’s walls.
(b) What do you conclude about the property of matter from the given picture?
Answer: We conclude that air (matter) occupies space and has volume.
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