Case Study Questions for Class 9 Science Chapter 1 Matter in Our Surroundings

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Board	CBSE
Useful for	Class 9 Students
Subject	Science
Chapter	Chapter 1 Matter in Our Surroundings
Question Type	Case Study Questions
No. of Questions	5
With Answers	Yes
Important Link	Class 9 Chapterwise Case Study

Table of Contents

Case Study Questions for Class 9 Science Chapter 1 Matter in Our Surroundings

Here we are providing case study questions for class 9 science chapter 1 Matter in Our Surroundings. Students are suggested to go through each and every case study questions for better understanding of the chapter.

Case Study/Passage Based Questions:

Case Study Question 1:

Read the following passage and answer the questions given below.

Every matter is made up of tiny particles. These particles are so tiny that they can’t be seen with naked eyes.

The three characteristics shown by particles of matter are as follows:

(i) There are small voids between particles in a matter. This characteristic is the concept behind the solubility of a substance in other substances.

(ii) Particles of matter show continuous random movements, that is they possess kinetic energy. The spreading of ink in a beaker of glass, smell of agarbattis, etc. are few illustrations that show the movement of particles of a substance.

(iii) The particles of matter attract each other with a force called interparticle force of attraction.
Read the given passage carefully and give the answer of the following questions:

Q 1. Spreading of fragrance of a burning incense stick in a room shows that:
a. particles of matter have spaces between them.
b. particles of matter attract each other.
c. particles of matter are constantly moving.
d. None of the above

Q 2. What happens when we add sugar to water?
a. Volume of water doubles.
b. Volume of water decreases
c. Volume of water remains the same.
d. None of the above

Q 3. A stream of water cannot be cut by fingers. Which property of matter does this observation show?
a. Particles of matter attract each other.
b. Particles of matter have spaces between them.
c. Particles of matter are continuously moving.
d. None of the above

Q 4. When we put some crystals of potassium permanganate in a beaker containing water, we observe that after some time, the whole water turns pink. This intermixing of particles of two different types of matter on their own is called:
a. Brownian motion
b. melting
c. sublimation
d. diffusion

Q 5. Why is the rate of diffusion of liquids higher than that of solids?
a. In the liquid state, particles are tightly packed as compared to solids.
b. In the liquid state, particles move freely as compared to solids.
c. In solid state, particles have least force of attraction between the particles.
d. In solid state, particles cannot be compressed easily.

Answers

(c) particles of matter are constantly moving.
(c) Volume of water remains the same.
(a) Particles of matter attract each other.
(d) diffusion
(b) In the liquid state, particles move freely as compared to solids

Case Study Question 2:

Understanding States of Matter

Read the following passage and answer the questions given below.

A group of students conducted an experiment in which they heated a solid substance in a beaker. As the temperature increased, the solid first melted into a liquid and then gradually turned into vapour. During the phase change from solid to liquid, they noticed that the temperature remained constant even though heat was continuously supplied. One curious student asked, “Where does the heat go if the temperature is not increasing?”

Case Study Questions for Class 9 Science Chapter 1 Matter in Our Surroundings - 1

Q1. What is the name of the heat energy absorbed during the change from solid to liquid without a change in temperature?
Ans. Latent heat of fusion.

Q2. Why does the temperature remain constant during the melting of a solid?
Ans. The temperature remains constant because the heat energy supplied is used to overcome the forces of attraction between the particles of the solid, changing it into a liquid. This energy does not increase kinetic energy, hence temperature stays constant.

Q3. Which property of matter allows it to exist in different states (solid, liquid, gas)?
Ans. The property of inter-particle forces of attraction and kinetic energy of particles determines the state of matter.

Q4. If 100 grams of ice at 0°C is converted into water at 0°C, what kind of energy change has occurred, and what remains unchanged?
Ans. The ice absorbs latent heat of fusion to become water, indicating a change in internal energy. The temperature remains unchanged at 0°C.

Case Study Question 3:

Evaporation and Everyday Life

Read the following passage and answer the questions given below.

Ravi hung his wet clothes on a windy day. He noticed that the clothes dried faster than usual. His sister asked why the clothes dried more quickly. Ravi recalled his science lesson, which mentioned that the rate of evaporation depends on several factors such as temperature, surface area, wind speed, and humidity. He also observed that when he rubbed alcohol on his hand, it felt cool.

Case Study Questions for Class 9 Science Chapter 1 Matter in Our Surroundings - 2

Q1. Why did Ravi’s clothes dry faster on a windy day?
Ans. Because increased wind speed helps to remove the water vapour from the surface of clothes faster, increasing the rate of evaporation.

Q2. How does evaporation cause cooling, as observed in the alcohol example?
Ans. During evaporation, particles absorb heat from the surface (in this case, the skin) to gain energy and escape. This heat loss from the surface causes a cooling effect.

Q3. If the humidity is high, how will it affect the rate of evaporation?
Ans. High humidity means the air already contains a lot of water vapour, so evaporation slows down as the air cannot accept more moisture easily.

Q4. Give one reason why evaporation of sweat is essential for the human body.
Ans. Evaporation of sweat cools the body and helps regulate body temperature, preventing overheating.

Case Study Question 4:

Interconversion of States

Read the following passage and answer the questions given below.

In a chemistry lab, students are observing dry ice (solid carbon dioxide). One student notices that it directly changes into a gaseous state without becoming liquid. The teacher explains this process and compares it with camphor burning, which also seems to disappear without leaving any liquid behind. This led to a discussion on conditions under which substances change their state.

Q1. What is the name of the process by which dry ice changes directly into a gas?
Ans. Sublimation.

Q2. Name one more substance (other than dry ice and camphor) that undergoes the same type of change.
Ans. Naphthalene.

Q3. What condition of pressure and temperature is usually required for sublimation?
Ans. Sublimation typically occurs at low pressure and/or specific temperatures unique to the substance, where it bypasses the liquid state.

Q4. How can knowledge of sublimation be applied in daily life or industries?
Ans. It is used in the purification of substances like camphor or naphthalene and also in making dry ice-based refrigeration and fog machines in events.

Case Study Question 5:

Role of Temperature and Pressure in Changing States

Read the following passage and answer the questions given below.

In a pressurized canister, liquefied petroleum gas (LPG) is stored as a liquid. When released into the air, it comes out as a gas. Similarly, oxygen tanks used in hospitals store oxygen in compressed form. The teacher explains that temperature and pressure play a crucial role in determining the state of matter.

Case Study Questions for Class 9 Science Chapter 1 Matter in Our Surroundings - 4

Q1. Why is LPG stored as a liquid under high pressure but used as a gas in homes?
Ans. Under high pressure, gases can be compressed into a liquid state for easy storage and transport. When pressure is released, it turns back into gas which is easier to use for combustion in homes.

Q2. How does decreasing the pressure affect the boiling point of a liquid?
Ans. Decreasing pressure lowers the boiling point of a liquid because less energy is needed for particles to escape into the vapour phase.

Q3. What would happen if pressure is suddenly released from a gas stored at high pressure?
Ans. The gas will rapidly expand and cool down, possibly forming mist or frost due to sudden evaporation and pressure drop.

Q4. Explain why mountain cooking takes longer compared to cooking at sea level, in terms of boiling point.
Ans. At high altitudes, atmospheric pressure is lower, so water boils at a temperature lower than 100°C, resulting in slower cooking due to less heat energy in boiling water.

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