Chapter 1: Matter in Our Surroundings Case Study Questions | science Class 9 CBSE

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Chapter 1: Matter in Our Surroundings Case Study Questions | science Class 9 CBSE | ByteNotes.in

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Case Set 1

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Ravi placed a drop of Dettol in a beaker of water and noticed that the smell spread throughout the room even after several dilutions.

Question 1: Q1. What does this activity suggest about particles of matter?

Particles of matter are extremely small in size.
They keep dividing into finer particles during dilution.
Even in small quantity, they can spread widely through a medium.

Question 2: Q2. Why does the smell spread throughout the room?

Particles of matter are continuously moving.
They diffuse through air and mix with surrounding particles.
Movement increases with energy from the surroundings.

Question 3: Q3. Which property of matter is responsible for this observation?

Particles of matter are in constant motion.
They occupy spaces between other particles.
They have the ability to diffuse and spread on their own.

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Case Set 2

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An incense stick was placed at one corner of a room. Within minutes, students on the other side could smell it.

Question 1: Q1. Why did the smell reach everyone in the room?

The particles of the incense stick spread via diffusion.
Gaseous particles move rapidly in all directions.
Air currents help disperse the particles across the room.

Question 2: Q2. Which characteristic of particles is illustrated here?

They are continuously moving.
They can diffuse quickly in gases.
They possess kinetic energy that increases with temperature.

Question 3: Q3. Why does heating the incense stick increase the smell?

It increases the kinetic energy of particles.
Warmer air accelerates the diffusion process.
More aroma particles are released into the air.

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Case Set 3

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Sonal added sugar to water in a beaker and stirred. The sugar disappeared, and there was no visible change in the water level.

Question 1: Q1. What conclusion can be drawn from this observation?

Sugar particles occupy spaces between water particles.
Matter is made up of particles with space between them.
Dissolution does not necessarily increase volume visibly.

Question 2: Q2. What does this tell us about the structure of matter?

Particles of matter are not tightly packed in all substances.
Even solids like sugar can mix with liquids due to intermolecular gaps.
The arrangement allows mixing at the particle level.

Question 3: Q3. Which property of matter is demonstrated here?

Particles of matter have space between them.
They are capable of intermixing with other substances.
They adjust into available spaces without increasing bulk volume.

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Case Set 4

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A drop of blue ink was slowly added to a beaker of still water. The ink slowly spread without any stirring and eventually colored the entire beaker.

Question 1: Q1. Why did the ink spread in the water without stirring?

Particles of ink and water intermix on their own.
Diffusion occurs even without external force.
Particles move from higher to lower concentration naturally.

Question 2: Q2. What does this experiment demonstrate?

Matter is composed of particles that move constantly.
Diffusion is a result of particle movement.
Liquids have enough space to allow particle motion and mixing.

Question 3: Q3. How does temperature affect this process?

Higher temperature increases particle speed.
Warm water would cause faster diffusion of ink.
Temperature boosts kinetic energy of the particles involved.

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Case Set 5

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During summer, Rahul noticed his clothes dried faster on a windy day than on a humid one. His teacher explained that it is due to evaporation.

Question 1: Q1. What factors increased the rate of evaporation here?

Wind speed carries water vapour away.
Dry air reduces humidity and allows more evaporation.
Sunlight increases temperature, enhancing particle energy.

Question 2: Q2. Why does humidity slow down evaporation?

Air already contains a lot of water vapour.
It reduces the rate at which new vapours can escape.
High humidity saturates the air, limiting evaporation.

Question 3: Q3. What daily practices use this concept?

Spreading clothes out in windy, sunny areas for drying.
Cooling rooms by sprinkling water on floors/roofs.
Using fans to increase wind speed during drying.

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Chapter sections

Chapter 1: Matter in Our Surroundings | Case Study Questions

Passage

Question 1: Q1. What does this activity suggest about particles of matter?

Question 2: Q2. Why does the smell spread throughout the room?

Question 3: Q3. Which property of matter is responsible for this observation?

Passage

Question 1: Q1. Why did the smell reach everyone in the room?

Question 2: Q2. Which characteristic of particles is illustrated here?

Question 3: Q3. Why does heating the incense stick increase the smell?

Passage

Question 1: Q1. What conclusion can be drawn from this observation?

Question 2: Q2. What does this tell us about the structure of matter?

Question 3: Q3. Which property of matter is demonstrated here?

Passage

Question 1: Q1. Why did the ink spread in the water without stirring?

Question 2: Q2. What does this experiment demonstrate?

Question 3: Q3. How does temperature affect this process?

Passage

Question 1: Q1. What factors increased the rate of evaporation here?

Question 2: Q2. Why does humidity slow down evaporation?

Question 3: Q3. What daily practices use this concept?

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