Matter in Our Surroundings Class 9 Notes, Summary, Questions & MCQs

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Class 9 chapter Matter in Our Surroundings notes, summary, MCQs, keywords, and exam questions for quick revision and exams.

Introduction of the Chapter

The chapter Matter in Our Surroundings is one of the foundational topics in Class 9 Chemistry. It helps students understand what matter is, its properties, and how it changes under different conditions. Everything around us — air, water, food, plants, metals, and even our bodies — is made up of matter.

In Matter in Our Surroundings, students learn that matter occupies space and has mass. The chapter explains the particle nature of matter, states of matter, changes in states, evaporation, and factors affecting evaporation.

Understanding Matter in Our Surroundings is essential because it builds the base for advanced chemistry concepts and helps explain everyday phenomena like melting ice, boiling water, drying clothes, and the smell of perfume spreading in a room.

Short Notes

Matter is anything that has mass and occupies space.
Matter is made up of tiny particles.
Particles of matter have spaces between them.
Partices are continuously moving (kinetic energy).
Particles attract each other.
States of matter: Solid, Liquid, Gas.
Interconversion of states occurs by changing temperature and pressure.
Melting point: Temperature at which solid becomes liquid.
Boiling point: Temperature at which liquid becomes gas.
Latent heat: Heat required to change state without changing temperature.
Evaporation occurs below boiling point.
Factors affecting evaporation: surface area, temperature, humidity, wind speed.

Detailed Summary (Matter in Our Surroundings)

The chapter Matter in Our Surroundings explains that everything around us is made of matter. Matter has mass and occupies space. Ancient Indian philosophers classified matter based on five elements, while modern science classifies matter based on physical properties and particle nature.

Particle Nature of Matter

Matter is made up of very tiny particles. These particles are too small to be seen with naked eyes. For example, when sugar dissolves in water, the particles spread evenly throughout the water.

Characteristics of Particles of Matter

1. Particles have spaces between them
When sugar dissolves in water, it disappears because sugar particles fill spaces between water particles.

2. Partices are continuously moving
Particles possess kinetic energy. The movement increases with temperature, which is why diffusion occurs faster in hot water.

3. Particles attract each other
There is a force of attraction between particles that keeps them together. This force is strongest in solids and weakest in gases.

States of Matter

Matter exists in three main states:

Solids

Fixed shape and volume
Particles tightly packed
Very strong intermolecular force
Example: wood, iron, ice

Liquids

Fixed volume but no fixed shape
Particles loosely packed
Flow easily
Example: water, milk, oil

Gases

No fixed shape or volume
Partices move freely
Very weak attraction forces
Example: air, oxygen, carbon dioxide

Change of State of Matter

Matter can change its state by changing temperature or pressure.

Effect of Temperature

Melting (Fusion): Solid → Liquid
Example: ice melts into water.

Freezing: Liquid → Solid

Vaporization: Liquid → Gas
Example: water boiling into steam.

Condensation: Gas → Liquid

Sublimation: Solid directly → Gas
Example: camphor, naphthalene.

Latent Heat

Latent heat is the heat absorbed or released during change of state without change in temperature.

Latent heat of fusion: heat needed to convert solid to liquid.
Latent heat of vaporization: heat needed to convert liquid to gas.

Effect of Pressure

Applying pressure and reducing temperature can convert gases into liquids. LPG and CNG are stored as compressed gases.

Evaporation

Evaporation is the process by which liquid changes into vapor at temperatures below its boiling point.

Factors Affecting Evaporation

Surface area: larger area → faster evaporation
Temperature: higher temperature → faster evaporation
Humidity: lower humidity → faster evaporation
Wind speed: higher wind speed → faster evaporation

Evaporation causes cooling. This is why we feel cool after sweating.

The concepts in Matter in Our Surroundings help explain daily life processes and build strong scientific understanding.

Flowchart / Mind Map

Matter
│
├── Particle Nature
│ ├── Spaces between particles
│ ├── Motion
│ └── Attraction
│
├── States of Matter
│ ├── Solid
│ ├── Liquid
│ └── Gas
│
├── Change of State
│ ├── Melting
│ ├── Freezing
│ ├── Vaporization
│ ├── Condensation
│ └── Sublimation
│
└── Evaporation
├── Surface Area
├── Temperature
├── Humidity
└── Wind Speed

Important Keywords with Meanings

Matter: Anything that has mass and occupies space.
Diffusion: Mixing of particles on their own.
Kinetic Energy: Energy possessed by moving particles.
Intermolecular Force: Force of attraction between particles.
Melting Point: Temperature at which solid melts.
Boiling Point: Temperature at which liquid boils.
Latent Heat: Heat absorbed without temperature change.
Evaporation: Surface conversion of liquid into vapor.
Sublimation: Solid changing directly into gas.
Condensation: Gas changing into liquid.

Important Questions & Answers

Very Short Answer Questions

What is matter?
Matter is anything that has mass and occupies space.
Why do gases compress easily?
Because particles are far apart with large spaces.
What is diffusion?
The intermixing of particles on their own.
Define melting point.
Temperature at which solid changes into liquid.
What is sublimation?
Solid directly converting into gas.
Why do we feel cool after sweating?
Evaporation of sweat absorbs heat.
Name factors affecting evaporation.
Surface area, temperature, humidity, wind speed.
Why do solids have fixed shape?
Strong force of attraction between particles.
What is latent heat?
Heat absorbed during state change without temperature rise.
Why does diffusion increase with temperature?
Particles move faster at higher temperature.

Short Answer Questions

Explain characteristics of particles of matter.
Particles have spaces, are in motion, and attract each other. These properties explain diffusion, compressibility, and states of matter.
Differentiate between solids, liquids, and gases.
Solids have fixed shape and strong forces; liquids have fixed volume and flow; gases have no fixed shape and weak forces.
Explain interconversion of states of matter.
Matter changes state by temperature and pressure changes through melting, freezing, vaporization, condensation, and sublimation.
What is latent heat? Explain types.
Latent heat is heat absorbed during state change. Types include latent heat of fusion and vaporization.
Explain evaporation and factors affecting it.
Evaporation is surface vaporization influenced by temperature, humidity, surface area, and wind speed.
Why does evaporation cause cooling?
Particles absorb heat to escape into vapor, lowering surrounding temperature.
Explain effect of pressure on gases.
High pressure compresses gases into liquids, used in LPG storage.
What is sublimation? Give examples.
Direct conversion of solid to gas. Examples: camphor, dry ice.
Why are gases highly compressible?
Large spaces between particles allow compression.
Explain importance of Matter in Our Surroundings in daily life.
It explains cooking, drying clothes, cooling by sweat, gas storage, and weather processes.

30 MCQs with Answers

Matter occupies
A. space ✔
B. time
C. light
D. energy
Particles of matter are
A. stationary
B. moving ✔
C. invisible only
D. cold
Strongest force of attraction is in
A. gases
B. liquids
C. solids ✔
D. plasma
Diffusion is fastest in
A. solids
B. liquids
C. gases ✔
D. ice
Ice melts at
A. 0°C ✔
B. 50°C
C. 100°C
D. -10°C
Boiling point of water is
A. 50°C
B. 100°C ✔
C. 150°C
D. 0°C
Evaporation occurs at
A. any temperature ✔
B. boiling point only
C. freezing point
D. 0°C
Latent heat is
A. sensible heat
B. hidden heat ✔
C. solar heat
D. kinetic heat
Which shows sublimation?
A. salt
B. camphor ✔
C. sand
D. sugar
Liquids have
A. fixed shape
B. fixed volume ✔
C. no mass
D. no particles
Gases are compressible due to
A. heavy particles
B. large spaces ✔
C. strong forces
D. solid nature
Diffusion increases with
A. cold
B. pressure
C. temperature ✔
D. darkness
Sweat cools body due to
A. condensation
B. evaporation ✔
C. freezing
D. melting
Wind speed ___ evaporation.
A. slows
B. increases ✔
C. stops
D. freezes
Humidity ___ evaporation.
A. increases
B. decreases ✔
C. stops
D. freezes
Solid → gas is
A. melting
B. sublimation ✔
C. freezing
D. condensation
Gas → liquid is
A. condensation ✔
B. fusion
C. sublimation
D. freezing
LPG is stored as
A. liquid under pressure ✔
B. solid
C. gas at room pressure
D. plasma
Particles attract each other due to
A. gravity
B. intermolecular force ✔
C. friction
D. heat
Evaporation causes
A. heating
B. cooling ✔
C. melting
D. freezing
Diffusion is mixing of
A. solids
B. particles ✔
C. liquids only
D. gases only
Kinetic energy increases with
A. cold
B. temperature ✔
C. humidity
D. pressure
Matter exists in ___ states.
A. two
B. three ✔
C. four
D. five
Water vapour is
A. solid
B. liquid
C. gas ✔
D. plasma
Melting is also called
A. fusion ✔
B. freezing
C. sublimation
D. condensation
Freezing is
A. liquid → solid ✔
B. solid → liquid
C. gas → liquid
D. liquid → gas
Which spreads smell fastest?
A. perfume ✔
B. stone
C. metal
D. wood
Ice is
A. liquid
B. solid ✔
C. gas
D. plasma
Milk is
A. solid
B. liquid ✔
C. gas
D. vapor
Oxygen is
A. liquid
B. gas ✔
C. solid
D. plasma

Exam Tips & Value-Based Questions

Exam Tips

Learn definitions exactly as given.
Practice diagrams and flowcharts.
Understand evaporation & cooling concept.
Revise differences between states of matter.
Practice MCQs for quick revision.

Value-Based Questions

Why should we dry clothes in sunlight and wind?
Because evaporation is faster in heat and wind.
Why is sweating important for the body?
It helps cool the body through evaporation.
Why should LPG cylinders be handled carefully?
They contain compressed gas under high pressure.
Why are earthen pots used to cool water?
Water evaporates through pores causing cooling.
Why should we avoid leaving perfume bottles open?
Perfume evaporates quickly and gets wasted.

Conclusion (Matter in Our Surroundings)

The chapter Matter in Our Surroundings forms the foundation of scientific understanding about the physical world. It introduces students to the concept that everything around us is made of matter, which has mass and occupies space. This simple idea helps learners connect science with daily life experiences such as melting ice, boiling water, drying clothes, and the spreading of fragrance.

One of the most important lessons from Matter in Our Surroundings is the particle nature of matter. Matter is made up of extremely tiny particles that cannot be seen with the naked eye. These particles have spaces between them, are in constant motion, and attract each other. These characteristics explain why substances diffuse, dissolve, and change states.

The chapter explains the three primary states of matter: solids, liquids, and gases. Solids have fixed shape and volume because their particles are tightly packed and strongly attracted to each other. Liquids have fixed volume but take the shape of their container due to weaker forces of attraction. Gases have neither fixed shape nor fixed volume because their particles move freely with very weak intermolecular forces.

Understanding the interconversion of states is another key concept discussed in Matter in Our Surroundings. By changing temperature and pressure, matter can change from one state to another. Processes such as melting, freezing, vaporization, condensation, and sublimation demonstrate how matter transforms under different conditions.

Latent heat plays a vital role during state changes. During melting or boiling, heat energy is absorbed without any rise in temperature because it is used to overcome intermolecular forces. This concept explains why temperature remains constant during melting and boiling.

Evaporation is an important surface phenomenon explained in Matter in Our Surroundings. Unlike boiling, evaporation occurs at temperatures below the boiling point. It is influenced by surface area, temperature, humidity, and wind speed. The cooling effect of evaporation is observed in sweating, earthen pots cooling water, and desert coolers.

The chapter also highlights the effect of pressure on gases. By increasing pressure and lowering temperature, gases can be liquefied. This principle is used in storing gases like LPG and CNG for domestic and industrial use.

The knowledge gained from Matter in Our Surroundings is not limited to textbooks. It helps us understand real-life applications such as refrigeration, gas storage, weather changes, and cooling mechanisms in the human body. It also builds a scientific attitude and encourages students to observe and question everyday phenomena.

From an examination perspective, this chapter is extremely important. Questions frequently appear on states of matter, evaporation, latent heat, and particle theory. Understanding concepts rather than memorizing facts helps students answer both theoretical and application-based questions effectively.

In conclusion, Matter in Our Surroundings provides a strong conceptual base for further studies in chemistry and physics. It explains how matter behaves, changes, and interacts with energy. By mastering this chapter, students develop scientific thinking skills and gain a deeper understanding of the world around them.

Long Question Answer 💫

1. Explain the characteristics of particles of matter.

Particles of matter have three main characteristics:

1. Partices have spaces between them
When sugar is dissolved in water, it disappears because sugar particles occupy the spaces between water particles.

2. Particles are continuously moving
Particles possess kinetic energy and keep moving constantly. When temperature increases, particle movement increases, which speeds up diffusion.

3. Partices attract each other
There is a force of attraction between particles that holds them together. This force is strongest in solids and weakest in gases.

These characteristics explain the behavior and physical properties of matter.

2. Describe the three states of matter with their properties.

Matter exists in three main states: solids, liquids, and gases.

Solids

Fixed shape and volume
Strong intermolecular forces
Particles tightly packed
Do not flow
Example: wood, ice, metal

Liquids

Fixed volume but no fixed shape
Weaker force of attraction than solids
Flow easily
Example: water, milk, oil

Gases

No fixed shape or volume
Very weak intermolecular forces
Highly compressible
Example: air, oxygen, carbon dioxide

3. Explain interconversion of states of matter.

Matter can change from one state to another by changing temperature or pressure.

Melting (Fusion): Solid → Liquid
Freezing: Liquid → Solid
Vaporization: Liquid → Gas
Condensation: Gas → Liquid
Sublimation: Solid → Gas (without becoming liquid)

Example: Ice melts into water, and water boils into steam.

4. What is latent heat? Explain its types.

Latent heat is the heat absorbed or released during the change of state of a substance without any change in temperature.

Latent heat of fusion:
Heat required to convert solid into liquid at melting point.
Example: ice → water.

Latent heat of vaporization:
Heat required to convert liquid into gas at boiling point.
Example: water → steam.

This heat is used to overcome intermolecular forces.

5. Explain evaporation and factors affecting it.

Evaporation is the process by which a liquid changes into vapor at temperatures below its boiling point.

Factors affecting evaporation:

Surface area → larger area increases evaporation
Temperature → higher temperature increases evaporation
Humidity → lower humidity increases evaporation
Wind speed → higher wind speed increases evaporation

Evaporation causes cooling because heat is absorbed from surroundings.

6. Why does evaporation cause cooling?

During evaporation, particles at the surface gain energy and escape into the air. They absorb heat energy from the surroundings to do so.

As heat is removed from the surface, the temperature drops, producing a cooling effect.

Examples:

sweating cools the body
water in earthen pots becomes cool
desert coolers cool air

7. Explain diffusion and factors affecting diffusion.

Diffusion is the intermixing of particles of two substances on their own.

Examples:

smell of perfume spreads in a room
ink spreads in water

Factors affecting diffusion:

temperature (higher → faster diffusion)
state of matter (fastest in gases)
size of particles (smaller → faster diffusion)

Diffusion proves that particles of matter are in motion.

8. Explain the effect of pressure and temperature on matter.

Temperature and pressure affect the state of matter.

Effect of temperature:

increases kinetic energy
particles move faster
solid → liquid → gas

Effect of pressure:

compresses particles closer
gas → liquid conversion possible

Example: LPG is stored as liquid under high pressure.

9. What is sublimation? Explain with examples.

Sublimation is the process in which a solid directly changes into gas without passing through the liquid state.

Examples:

camphor
naphthalene balls
dry ice (solid CO₂)

During sublimation, particles gain energy and escape directly into the air.

10. Explain the importance of Matter in Our Surroundings in daily life.

The concepts of this chapter explain many everyday phenomena:

sweating cools our body (evaporation)
drying clothes in sunlight (evaporation)
LPG storage (pressure and liquefaction)
melting ice and freezing water (state change)
perfume smell spreading (diffusion)
earthen pots cooling water (evaporation cooling)

Understanding matter helps us explain natural processes and technological applications.

Assertion Reason 💫

Directions:

For each question, choose the correct option:

A. Both Assertion (A) and Reason (R) are true, and R is the correct explanation of A.
B. Both A and R are true, but R is not the correct explanation of A.
C. A is true, but R is false.
D. A is false, but R is true.

1.

Assertion (A): Solids have a definite shape.
Reason (R): Particles in solids are closely packed with strong forces of attraction.

Answer: A
Explanation: Strong forces hold particles in fixed positions, giving solids a definite shape.

2.

Assertion (A): Gases are highly compressible.
Reason (R): There are large spaces between gas particles.

Answer: A
Explanation: Large intermolecular spaces allow gas particles to be compressed easily.

3.

Assertion (A): Diffusion occurs faster at higher temperatures.
Reason (R): Particles gain kinetic energy and move faster when heated.

Answer: A
Explanation: Increased kinetic energy increases particle movement, speeding diffusion.

4.

Assertion (A): Liquids can flow.
Reason (R): Particles in liquids are less tightly packed than in solids.

Answer: A
Explanation: Weaker attraction allows particles to slide past each other.

5.

Assertion (A): Evaporation causes cooling.
Reason (R): Partices of liquid absorb heat from surroundings to change into vapor.

Answer: A
Explanation: Heat absorption lowers surrounding temperature.

6.

Assertion (A): Ice melts at 0°C but temperature does not rise during melting.
Reason (R): Heat energy is used to overcome intermolecular forces.

Answer: A
Explanation: Heat supplied acts as latent heat of fusion rather than raising temperature.

7.

Assertion (A): Perfume smell spreads throughout a room.
Reason (R): Gas particles move randomly in all directions.

Answer: A
Explanation: Random motion of gas particles causes diffusion.

8.

Assertion (A): Evaporation increases with increase in humidity.
Reason (R): Air already contains more water vapor at high humidity.

Answer: D
Explanation: High humidity slows evaporation because the air cannot hold more vapor.

9.

Assertion (A): LPG is stored in liquid form.
Reason (R): Gases can be liquefied by applying pressure and lowering temperature.

Answer: A
Explanation: LPG is compressed and cooled to store it as liquid.

10.

Assertion (A): Sublimation occurs in camphor.
Reason (R): Camphor changes directly from solid to gas on heating.

Answer: A
Explanation: Sublimation is the direct solid-to-gas transition.

Important MCQs💫

1. Which of the following is not a form of matter?

A. Air
B. Water
C. Light
D. Ice

Answer: C

2. Matter is made up of

A. cells
B. particles ✔
C. tissues
D. energy

Answer: B

3. The force of attraction between particles is maximum in

A. gases
B. liquids
C. solids ✔
D. plasma

Answer: C

4. Which state of matter has the highest kinetic energy?

A. Solid
B. Liquid
C. Gas ✔
D. All equal

Answer: C

5. The process of gas changing into liquid is called

A. freezing
B. condensation ✔
C. sublimation
D. evaporation

Answer: B

6. Which of the following shows diffusion?

A. stone sinking in water
B. smell of food spreading ✔
C. ice melting
D. sugar crystallizing

Answer: B

7. The SI unit of temperature is

A. Celsius
B. Kelvin ✔
C. Fahrenheit
D. Joule

Answer: B

8. Which of the following has a fixed volume but no fixed shape?

A. Solid
B. Liquid ✔
C. Gas
D. Plasma

Answer: B

9. The boiling point of water on the Kelvin scale is

A. 273 K
B. 100 K
C. 373 K ✔
D. 212 K

Answer: C

10. Which process involves heat absorption?

A. freezing
B. condensation
C. melting ✔
D. cooling

Answer: C

11. Which substance undergoes sublimation?

A. wood
B. camphor ✔
C. salt
D. sugar

Answer: B

12. Increase in temperature causes particles to

A. stop moving
B. move slower
C. move faster ✔
D. disappear

Answer: C

13. Which of the following increases evaporation?

A. high humidity
B. low temperature
C. large surface area ✔
D. closed container

Answer: C

14. When steam cools, it changes into water. This process is

A. evaporation
B. condensation ✔
C. sublimation
D. freezing

Answer: B

15. Which state of matter fills the entire container?

A. solid
B. liquid
C. gas ✔
D. ice

Answer: C

16. Why can we smell incense sticks from a distance?

A. condensation
B. diffusion ✔
C. freezing
D. sublimation

Answer: B

17. Which of the following decreases evaporation?

A. high wind speed
B. high humidity ✔
C. high temperature
D. large surface area

Answer: B

18. Which process occurs when solid carbon dioxide changes directly into gas?

A. fusion
B. condensation
C. sublimation ✔
D. evaporation

Answer: C

19. Cooling produced during evaporation is due to

A. release of heat
B. absorption of heat ✔
C. freezing
D. condensation

Answer: B

20. Which of the following is an example of liquid changing into gas below boiling point?

A. boiling water
B. steam formation
C. evaporation ✔
D. freezing

Answer: C

Case Based question ❓

Case-Based Question 1

Case:
Ravi left a glass of water on his study table near a fan. After a few hours, he noticed that the water level had reduced.

Questions:

What process caused the reduction in water level?
List two factors that could have increased the rate of this process.
How does this process cause cooling?

Answers:

The reduction in water level is due to evaporation.
Factors increasing the rate of evaporation:
- Increased surface area (larger exposed surface)
- Increased air movement (fan blowing air)
- Higher temperature
Evaporation causes cooling because particles of water absorb heat from surroundings to escape as vapor.

Case-Based Question 2

Case:
A student observes that ice cubes in a glass of water melt faster on a sunny day than on a cloudy day.

Questions:

Why do ice cubes melt faster in sunlight?
What is the term for the heat absorbed without a change in temperature during melting?
Name the type of energy possessed by ice particles during melting.

Answers:

Ice cubes melt faster because temperature is higher, increasing kinetic energy of particles.
The heat absorbed is called latent heat of fusion.
Ice particles possess kinetic energy and absorb energy to overcome intermolecular forces.

Case-Based Question 3

Case:
During winter, a mother dries clothes by hanging them outside. The process seems slower than in summer.

Questions:

Identify the process responsible for drying.
Explain why drying is slower in winter.
Suggest two ways to speed up drying in winter.

Answers:

The process responsible is evaporation.
Drying is slower because temperature is low and humidity is high, reducing evaporation rate.
Ways to speed up drying:
- Use a heater or sunlight to increase temperature
- Hang clothes in a well-ventilated area to increase wind speed

Case-Based Question 4

Case:
A chemistry teacher shows a demonstration: solid naphthalene gradually disappears without leaving any liquid.

Questions:

Name the process taking place.
Give two other examples of substances that show this behavior.
Explain why the temperature does not rise during this process.

Answers:

The process is sublimation (solid → gas).
Other examples: camphor, solid carbon dioxide (dry ice).
Temperature does not rise because the heat energy is used to overcome intermolecular forces, not to increase temperature.

Case-Based Question 5

Case:
A cylinder of LPG is stored under high pressure in a gas shop.

Questions:

Why is LPG stored in liquid form under pressure?
What happens if the cylinder leaks?
Explain the role of pressure in the storage of gases.

Answers:

LPG is stored as a liquid because gases can be liquefied by applying pressure and reducing temperature.
If the cylinder leaks, LPG escapes rapidly as gas, which is flammable and can cause accidents.
Pressure reduces the volume of gas particles and allows more gas to be stored safely in liquid form.

Class 9 Science – Chemistry

Chapter: Matter in Our Surroundings

Maximum Marks: 50
Time: 2 Hours

Section A: Multiple Choice Questions (1 mark each – 10 Marks)

Choose the correct answer.

Matter is anything that has
A. mass and occupies space ✔
B. mass only
C. energy only
D. shape only
Particles of matter
A. are stationary
B. are moving ✔
C. do not attract each other
D. have no mass
Which state of matter is highly compressible?
A. Solid
B. Liquid
C. Gas ✔
D. Plasma
Melting of ice is an example of
A. condensation
B. fusion ✔
C. evaporation
D. sublimation
Diffusion of perfume in a room proves that
A. gases are compressible
B. particles of matter are in motion ✔
C. solids have fixed shape
D. liquids have fixed volume
Latent heat is
A. heat causing temperature rise
B. heat absorbed without temperature change ✔
C. heat given out during freezing only
D. none of these
The process by which a solid changes directly into gas is called
A. condensation
B. sublimation ✔
C. vaporization
D. fusion
Evaporation increases with
A. high humidity
B. low wind speed
C. large surface area ✔
D. low temperature
Condensation is
A. Gas → Liquid ✔
B. Liquid → Solid
C. Solid → Gas
D. Liquid → Gas
Which of the following affects evaporation?
A. Temperature ✔
B. Surface area ✔
C. Humidity ✔
D. All of the above ✔

Section B: Short Answer Questions (2 marks each – 10 Marks)

Answer briefly:

Define matter.
Give two examples of sublimation.
What is the difference between melting point and boiling point?
Name two factors that affect evaporation.
Explain why gases are compressible.
State the kinetic theory of matter in brief.
What is latent heat of vaporization?
Why does sweating cool the body?
Why do solids have fixed shape but liquids do not?
Explain why diffusion occurs faster in gases than liquids.

Section C: Long Answer Questions (5 marks each – 20 Marks)

Explain the particle nature of matter. Include its three main characteristics with examples.
Describe the three states of matter and explain their properties with suitable examples.
Explain the interconversion of states of matter. Give examples for each change of state.
Explain evaporation, factors affecting it, and why it causes cooling.

Section D: Value-Based/Case-Based Questions (2.5 Marks each – 10 Marks)

Case 1: A student left a cup of water near a fan, and the water level decreased after some hours.

Identify the process causing this.
Give two factors that increase this process.
Explain why this process causes cooling.

Case 2: A cylinder of LPG is stored under high pressure in a gas shop.

Why is LPG stored as liquid?
What will happen if the cylinder leaks?
Explain the role of pressure in storing gases safely.

Marking Scheme

Section A: 10 × 1 = 10
Section B: 10 × 2 = 20
Section C: 4 × 5 = 20
Section D: 4 × 2.5 = 10
Total = 50 Marks

Class 9 Chemistry – Matter in Our Surroundings

Solution – Full Chapter Test Paper (50 Marks)

Section A: Multiple Choice Questions (1 mark each – 10 Marks)

A. mass and occupies space – Matter is anything that has mass and takes up space.
B. are moving – Particles of matter are in constant motion.
C. Gas – Gases are highly compressible because particles are far apart.
B. fusion – Melting of ice is called fusion.
B. particles of matter are in motion – Diffusion occurs due to random motion of particles.
B. heat absorbed without temperature change – Latent heat is used to overcome forces, not to raise temperature.
B. sublimation – Solid changing directly into gas.
D. All of the above – Evaporation increases with high temperature, large surface area, low humidity, and higher wind speed.
A. Gas → Liquid – Condensation is the process of gas changing into liquid.
D. All of the above – Temperature, surface area, and humidity affect evaporation.

Section B: Short Answer Questions (2 marks each – 10 Marks)

Define matter:
Matter is anything that has mass and occupies space.
Examples of sublimation:
Camphor, naphthalene, dry ice (solid CO₂).
Difference between melting point and boiling point:

Melting point: Temperature at which a solid turns into liquid.
Boiling point: Temperature at which a liquid turns into gas.

Factors affecting evaporation:

Surface area – larger area → faster evaporation
Temperature – higher temperature → faster evaporation
Humidity – lower humidity → faster evaporation
Wind speed – higher wind → faster evaporation

Why gases are compressible:
Particles of gases are far apart, so they can be pushed closer by applying pressure.
Kinetic theory of matter:

Matter is made up of tiny particles
Particles are in constant motion
Particles attract each other
Spaces exist between particles

Latent heat of vaporization:
The heat absorbed by 1 kg of liquid to convert it into vapor at its boiling point without change in temperature.
Why sweating cools the body:
Evaporation of sweat absorbs heat from the skin, reducing body temperature.
Why solids have fixed shape but liquids do not:
Particles in solids are tightly packed and held by strong forces. In liquids, forces are weaker, so particles can move and take the shape of the container.
Why diffusion is faster in gases than liquids:
Particles in gases move faster and are far apart, so mixing occurs quickly.

Section C: Long Answer Questions (5 marks each – 20 Marks)

Particle nature of matter:

Particles have spaces between them: Allows substances to mix and gases to be compressible.
Particles are in motion: Movement increases with temperature, explains diffusion.
Particles attract each other: Keeps solids and liquids together.

Example: Sugar dissolving in water shows spaces and motion of particles.

Three states of matter:

State	Shape	Volume	Particle arrangement	Example
Solid	Fixed	Fixed	Tightly packed	Ice, wood
Liquid	No fixed shape	Fixed	Loosely packed	Water, milk
Gas	No fixed shape	No fixed volume	Far apart	Oxygen, air

Explanation:

Solids: particles vibrate, strong attraction
Liquids: flow, moderate attraction
Gases: move freely, weak attraction

Interconversion of states:

Change	Process	Example
Solid → Liquid	Melting/Fusion	Ice → Water
Liquid → Solid	Freezing	Water → Ice
Liquid → Gas	Vaporization/Boiling	Water → Steam
Gas → Liquid	Condensation	Steam → Water
Solid → Gas	Sublimation	Camphor, Dry Ice

Explanation:

Changes occur due to temperature and pressure.
Latent heat is absorbed or released during change of state.

Evaporation:

Definition: Liquid changes into vapor below boiling point.
Factors affecting evaporation: Surface area, temperature, humidity, wind speed.
Cooling effect: Particles absorb heat from surroundings to escape → temperature drops.
Example: Sweating, water cooling in earthen pots.

Section D: Value-Based/Case-Based Questions (2.5 Marks each – 10 Marks)

Case 1: Cup of water near fan

Process: Evaporation.
Factors increasing evaporation: Surface area, wind speed, temperature.
Cooling effect explanation: Heat absorbed from water and surroundings lowers temperature.

Case 2: LPG cylinder storage

Reason for storing LPG as liquid: Gas is liquefied under high pressure and low temperature for safe storage.
Consequence of leakage: LPG escapes as flammable gas, may cause fire/explosion.
Role of pressure: Pressure reduces gas volume, allowing safe liquid storage and transportation.

✅ Total Marks: 50