Chapter 1 -MATTER IN OUR SURROUNDINGS -Class 9 – Simplified notes

What is Matter?

• Matter is anything around us that has the following properties:
  • It occupies space.
  • It has mass (can be weighed).
• Matter can be found in different forms like solids, liquids, and gases.

Also Check – Rapid Revision –Chapter 1- Matter In Our Surroundings – Class 9 Science

Examples of Matter

• Matter includes:
  • Air we breathe.
  • Water we drink.
  • Food we eat.
  • Objects like stones, plants, animals, clouds, and stars.
  • Even very small things like a drop of water or a grain of sand are also matter.

What is NOT Matter?

• Feelings like love, anger, thoughts, and smell are not matter because they do not have mass or occupy space.

Characteristics of Matter

1. Mass
   • Matter has weight, no matter how big or small the object is.
   • Example:
     • A stone is heavier than a piece of paper because it has more mass.
2. Volume
   • Matter takes up space.
   • Example:
     • A glass of water fills the glass completely, showing it occupies space.

Historical Perspective: Panch Tatva and Ancient Classifications

Panch Tatva (Five Elements)

• Early Indian philosophers believed that everything in the world, living or non-living, is made up of five basic elements, called Panch Tatva:
  • Air (Vayu)
  • Earth (Prithvi)
  • Fire (Agni)
  • Sky (Aakash)
  • Water (Jal)

Ancient Greek Philosophy

• Greek philosophers had a similar idea about matter being made of basic elements.
• Both ideas aimed to explain the diversity of materials in the world.

Also Check – 82 Reasoning-Based Questions & Answers-Matter In Our Surroundings  -Class 9 Science

Physical Nature of Matter

Matter is Made Up of Particles

• Matter is not continuous like a block of wood. It is made of tiny particles that are too small to see with our eyes.

Activity to Prove This: Dissolving Salt or Sugar in Water

1. Steps:
   • Take a glass of water.
   • Add a spoonful of sugar or salt to it.
   • Stir the water until the sugar/salt disappears.
2. Observation:
   • The sugar or salt “disappears,” but the water tastes sweet or salty.
   • The water level does not rise even after the sugar is added.
3. Conclusion:
   • Sugar/salt is made of tiny particles that mix with water particles and spread out in the spaces between them.

Also Check – Chapter 1- Matter In Our Surroundings – Class 9 Science – Very Short Question and Answers

Particles of Matter are Very Small

• The particles of matter are so small that they cannot be seen directly.
• Even a tiny crystal contains millions of these particles.

Activity to Show How Small They Are: Dilution of Potassium Permanganate

1. Steps:
   • Take a glass of water and add a few crystals of potassium permanganate (a purple-colored substance).
   • Stir until the water turns purple.
   • Take 10 mL of this purple solution and mix it with 90 mL of plain water in another glass.
   • Repeat this process 5–6 times, each time taking 10 mL of the solution and adding it to 90 mL of water.
2. Observation:
   • Even after multiple dilutions, the water still has a light purple color.
3. Conclusion:
   • Just a few crystals contain millions of tiny particles that spread and color the water, proving that particles of matter are incredibly small.

States of Matter

• Matter exists in three main states:
  • Solid
  • Liquid
  • Gas
• The state depends on:
  • Arrangement of particles.
  • Movement of particles.
  • Forces between particles.

The Solid State

Properties of Solids

1. Definite Shape and Volume:
   • Solids have fixed shapes and occupy a specific volume.
   • Example: A book or a pen.
2. Rigidity:
   • Solids do not flow and maintain their shape.
   • Example: A wooden block remains firm.
3. Negligible Compressibility:
   • Solids cannot be compressed easily because their particles are closely packed.
   • Example: A piece of iron does not shrink under pressure.

Special Cases in Solids

1. Rubber Bands:
   • A rubber band changes shape when stretched but regains its original shape when the force is removed.
   • It is considered a solid because it has definite mass and volume.
2. Salt and Sugar:
   • They take the shape of the container they are in, but their individual particles (crystals) retain their fixed structure.
3. Sponge:
   • A sponge can be compressed because it has tiny air holes.
   • These air pockets get squeezed, but the sponge is still a solid.

Also Check – Chapter 1- Matter In Our Surroundings – Class 9 Science – Long Question and Answers

The Liquid State

Properties of Liquids

1. No Fixed Shape:
   • Liquids take the shape of the container they are poured into.
   • Example: Water in a glass or a bowl.
2. Fixed Volume:
   • The amount of liquid remains the same, no matter the container.
   • Example: 50 mL of milk remains 50 mL whether in a cup or a bottle.
3. Fluidity:
   • Liquids can flow and be poured.
   • Example: Pouring juice from one glass to another.
4. Diffusion:
   • Liquids can mix with each other or with gases.
   • Example: Adding ink to water spreads the color evenly.

Diffusion in Liquids

• Liquids allow gases and other liquids to diffuse into them.
• Example:
  • Oxygen dissolves in water, allowing fish to breathe underwater.
  • Tea particles mix with water when making tea.

The Gaseous State

Properties of Gases

1. High Compressibility:
   • Gases can be compressed easily because their particles are far apart.
   • Example: Compressed natural gas (CNG) used in vehicles.
2. Diffusion:
   • Gases mix with other gases quickly.
   • Example: The smell of food travels through the air to other rooms.
3. Random Movement:
   • Gas particles move randomly and spread in all directions.
   • Example: Balloons inflate evenly because gas particles spread throughout the balloon.
4. Pressure Exertion:
   • Gas particles hit the walls of their container, exerting pressure.
   • Example: Air pressure in a tire keeps it inflated.

Also Check – Chapter 1- A Detailed Guide to “Matter and Its Properties” Activities for Class 9 Students

Comparison of Solids, Liquids, and Gases

Property	Solid	Liquid	Gas
Shape	Fixed	Takes shape of container	No fixed shape
Volume	Fixed	Fixed	No fixed volume
Compressibility	Negligible	Slightly compressible	Highly compressible
Flow	Does not flow	Flows easily	Flows and spreads quickly
Particle Arrangement	Tightly packed	Loosely packed	Very loosely packed

Change of State of Matter

• Matter can change from one state to another (solid ↔ liquid ↔ gas).
• The change occurs due to changes in temperature or pressure.

Effect of Temperature

Melting Point

• Melting: When a solid changes into a liquid by heating.
• The melting point is the temperature at which this occurs.
  • Example: Ice melts into water at 0°C (273 K).
• What Happens at the Particle Level?
  • Heat energy increases the movement of particles, weakening their fixed positions in the solid.

Boiling Point

• Boiling: When a liquid changes into a gas by heating.
• The boiling point is the temperature at which this occurs.
  • Example: Water boils into steam at 100°C (373 K).
• What Happens at the Particle Level?
  • Heat energy gives particles enough energy to break free from the liquid’s surface into the gaseous state.

Also Check – Chapter 1- Matter In Our Surroundings – Class 9 Science – Solved MCQs

Latent Heat

Latent Heat of Fusion

• The amount of heat energy required to convert 1 kg of a solid into a liquid at its melting point without changing the temperature.
  • Example: Ice absorbs heat to melt, but its temperature remains constant at 0°C.

Latent Heat of Vaporization

• The amount of heat energy required to convert 1 kg of a liquid into a gas at its boiling point without changing the temperature.
  • Example: Water absorbs heat to become steam, but its temperature remains constant at 100°C.

Also Check – Latent Heat of Fusion Formula- Easy Explanation with Formula & Examples

Also Check – What is Latent Heat? Fusion & Vaporization Explained with Real-Life Applications

Sublimation and Deposition

Sublimation

• A process where a solid changes directly into a gas without becoming a liquid.
  • Example: Camphor, naphthalene balls, or dry ice (solid CO₂).
• What Happens at the Particle Level?
  • Particles gain enough energy to directly escape into the gaseous state.

Also Check – Sublimation- How Solids Turn Into Gas Without Melting

Deposition

• A process where a gas changes directly into a solid without becoming a liquid.
  • Example: Frost formation or solid CO₂ forming under high pressure.

Effect of Pressure

Liquefaction of Gases

• Gases can be converted into liquids by:
  • Increasing pressure: Forces particles closer together.
  • Decreasing temperature: Reduces particle movement.
  • Example: Liquefied Petroleum Gas (LPG) is stored in cylinders by compressing gases under high pressure.

Solid Carbon Dioxide (Dry Ice)

• Solid CO₂ is stored under high pressure.
• On reducing the pressure, it changes directly into gas without becoming liquid (sublimation).
• Used in refrigeration and creating fog effects.

Also Check – NCERT Solutions for Class 9 Science Chapter 1- Matter In Our Surroundings

Key Processes for Change of State

Process	Change in State	Example
Melting	Solid → Liquid	Ice to water
Boiling	Liquid → Gas	Water to steam
Condensation	Gas → Liquid	Steam to water
Freezing	Liquid → Solid	Water to ice
Sublimation	Solid → Gas	Camphor, dry ice
Deposition	Gas → Solid	Frost forming on surfaces

Also Chekc – NCERT Exemplar Solutions- Class 9 Science Chapter – 1 – Matter in Our Surroundings

Evaporation

What is Evaporation?

Definition

• Evaporation is the process by which liquid particles at the surface gain enough energy to change into the gaseous state at any temperature below the boiling point.

Also Check – The Science of Evaporation – Process, Factors, and Applications

Phenomenon

• Only Surface Particles Evaporate:
  • Particles at the surface of the liquid absorb energy from the surroundings to overcome the forces of attraction and escape into the air as gas.
• Example:
  • Water in an open container gradually disappears over time due to evaporation.

Factors Affecting Evaporation

Several factors influence the rate at which evaporation occurs:

1. Surface Area

• Larger surface area increases evaporation.
  • More particles are exposed to air, allowing more of them to escape as gas.
  • Example:
    • Clothes dry faster when spread out compared to being folded.

2. Temperature

• Higher temperature increases evaporation.
  • Heat provides more energy for particles to escape into the air.
  • Example:
    • Water evaporates more quickly on a hot day than on a cold day.

3. Humidity

• Lower humidity increases evaporation.
  • Humidity is the amount of water vapor already present in the air.
  • If the air is already full of water vapor (high humidity), evaporation slows down.
  • Example:
    • Clothes take longer to dry on a humid day.

4. Wind Speed

• Higher wind speed increases evaporation.
  • Moving air carries away water vapor, leaving space for more liquid particles to evaporate.
  • Example:
    • Clothes dry faster on a windy day compared to a still day.

Also Check – Matter In Our Surroundings – Worksheet with Answer Key

Evaporation Causes Cooling

How It Happens

• During evaporation, liquid particles absorb energy from their surroundings to overcome the forces of attraction.
• This absorption of energy lowers the temperature of the surroundings, causing a cooling effect.

Examples

1. Sweating:
   • Sweat evaporates from our skin, taking heat from our body and making us feel cooler.
2. Sprinkling Water on the Floor:
   • In hot weather, water sprinkled on the floor evaporates, cooling the surface.
3. Acetone or Alcohol on the Palm:
   • Acetone or alcohol evaporates quickly, absorbing heat from the skin and making the palm feel cold.

Interconversion of States of Matter

• Matter can change from one state to another through specific processes.
• The change depends on conditions like temperature and pressure.

Processes of State Change

1. Melting

• Definition: The process where a solid changes into a liquid on heating.
• Example: Ice melting into water.
• Condition: Occurs at the melting point (e.g., ice melts at 0°C or 273 K).

2. Boiling

• Definition: The process where a liquid changes into gas on heating.
• Example: Water boiling into steam.
• Condition: Occurs at the boiling point (e.g., water boils at 100°C or 373 K).

3. Condensation

• Definition: The process where gas changes into a liquid on cooling.
• Example: Water vapor forming droplets on a cold glass surface.

4. Freezing

• Definition: The process where a liquid changes into a solid on cooling.
• Example: Water freezing into ice.
• Condition: Occurs at the freezing point (e.g., water freezes at 0°C or 273 K).

5. Sublimation

• Definition: The process where a solid directly changes into gas without becoming liquid.
• Example: Camphor, naphthalene balls, and dry ice (solid CO₂) sublimating.

6. Deposition

• Definition: The process where a gas directly changes into a solid without becoming liquid.
• Example: Frost forming on a cold surface.

Conditions Influencing State Changes

1. Temperature

• Effect:
  • Increasing temperature provides energy to particles, increasing their movement and causing a change in state (e.g., ice to water).
  • Decreasing temperature reduces energy, slowing particle movement and causing condensation or freezing.
• Example:
  • Heating water turns it into steam (boiling), while cooling water turns it into ice (freezing).

2. Pressure

• Effect:
  • Increasing pressure forces particles closer, changing a gas into a liquid or solid.
  • Reducing pressure allows particles to spread, changing a solid into a gas (e.g., sublimation of dry ice).
• Example:
  • Liquefied gases like LPG are stored under high pressure to remain liquid.

Key Points to Remember

Process	Change in State	Example	Conditions
Melting	Solid → Liquid	Ice to water	Increase in temperature
Boiling	Liquid → Gas	Water to steam	Increase in temperature
Condensation	Gas → Liquid	Steam to water	Decrease in temperature
Freezing	Liquid → Solid	Water to ice	Decrease in temperature
Sublimation	Solid → Gas	Camphor, dry ice sublimating	Increase in temperature or reduce pressure
Deposition	Gas → Solid	Frost formation	Decrease in temperature or increase pressure

Applications of Interconversion

• Refrigeration: Cooling and freezing involve condensation and freezing.
• Cooking: Boiling water and melting ice are examples of temperature-induced changes.
• Industrial Gases: Gases like LPG are liquefied under high pressure for storage and transportation.

Applications and Daily Life Examples

Diffusion in Gases and Liquids

What is Diffusion?

• Diffusion is the process by which particles of matter move from a region of higher concentration to a region of lower concentration.

Examples in Daily Life

1. Diffusion in Gases:
   • Example: The smell of food or perfume spreads across a room.
   • Gases diffuse faster because their particles move freely and are far apart.
2. Diffusion in Liquids:
   • Example: Adding ink to water spreads its color uniformly.
   • Liquids diffuse slower than gases because their particles are closer together.
3. Diffusion of Solids in Liquids:
   • Example: Sugar dissolving in water is a type of diffusion where particles of sugar mix with water particles.

Importance of Diffusion

• Essential for Life:
  • Oxygen diffuses from air into our blood and reaches body cells.
  • In aquatic life, oxygen dissolved in water (through diffusion) helps fish and plants survive.

Cooling Effects of Evaporation

How Evaporation Causes Cooling

• During evaporation, particles at the surface of a liquid absorb heat energy from the surroundings to escape into the gaseous state.
• This process removes heat from the surroundings, causing cooling.

Examples in Daily Life

1. Acetone (Nail Polish Remover):
   • When applied to the skin, acetone evaporates quickly, absorbing heat and making the skin feel cool.
2. Desert Coolers:
   • Water inside the cooler evaporates, taking heat from the air, and cools the surroundings.
3. Sprinkling Water on Hot Surfaces:
   • Water evaporates, reducing the heat of the surface.
4. Sweating:
   • Sweat evaporates from the skin, absorbing body heat and cooling it down.

Role of Diffusion in Survival

Aquatic Life

• Oxygen dissolves in water through diffusion, making it available to fish and aquatic plants for respiration.

Gas Exchange in Plants

• Carbon dioxide diffuses into leaves during photosynthesis.
• Oxygen produced in photosynthesis diffuses out of leaves.

Respiration in Animals

• Oxygen from air diffuses into the bloodstream through the lungs.
• Carbon dioxide diffuses out of the bloodstream into the air for exhalation.

Key Properties and Units

Key Properties and Their SI Units

Property	Definition	SI Unit	Symbol
Mass	The amount of matter in an object.	Kilogram	kg
Volume	The space occupied by an object.	Cubic metre	m³
Density	The mass of an object per unit volume.	Kilogram per cubic metre	kg/m³
Temperature	Measure of the average kinetic energy of particles in a substance.	Kelvin	K
Pressure	Force exerted per unit area.	Pascal	Pa
Length	The distance between two points.	Metre	m

Comparison of Properties Across States of Matter

Property	Solid	Liquid	Gas
Shape	Fixed	Takes shape of the container	No fixed shape
Volume	Fixed	Fixed	No fixed volume
Compressibility	Negligible	Very slight	Highly compressible
Particle Arrangement	Tightly packed	Loosely packed	Very loosely packed
Particle Movement	Vibrates in fixed positions	Moves more freely than solids	Moves randomly at high speeds
Interparticle Forces	Strong	Moderate	Weak
Diffusion	Very slow	Faster than solids	Very fast

Examples for Better Understanding

1. Solids:
   • Example: Iron, wood, ice.
   • Particles are tightly packed with strong forces of attraction.
2. Liquids:
   • Example: Water, oil, milk.
   • Particles are less tightly packed and can move past one another.
3. Gases:
   • Example: Air, carbon dioxide, steam.
   • Particles move randomly and have large spaces between them.