Matter

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1. Introduction to Matter

• Definition of Matter:
  Matter is anything that occupies space and has mass. It forms the physical “stuff” around us—from the air we breathe to the objects we use.

• Key Idea:
  Every object, whether living or non-living, is composed of matter.

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2. Classification of Matter

• Based on Composition:

  • Pure Substances:
    Matter that has a uniform and definite composition. It can be an element (like oxygen) or a compound (like water).
  • Mixtures:
    Matter composed of two or more pure substances that are not chemically combined. Mixtures can be:
    • Homogeneous (uniform composition, e.g., saltwater)
    • Heterogeneous (non-uniform, e.g., a salad)

• Based on States of Matter:

  • Solids
  • Liquids
  • Gases

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3. States of Matter and Their Characteristics

a. Solids

• Properties:
  • Fixed shape and volume
  • Particles are tightly packed
  • Particles vibrate in place
• Examples: Wood, ice, iron

b. Liquids

• Properties:
  • Fixed volume, shape of container
  • Particles are close but can move
  • Exhibit fluidity
• Examples: Water, oil, milk

c. Gases

• Properties:
  • No fixed shape or volume
  • Particles move freely and are far apart
  • Exert pressure on container walls
• Examples: Air, oxygen, nitrogen

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4. Particle Arrangement and Movement

• Solids: Particles are tightly packed and vibrate in place
• Liquids: Particles are loosely packed and move past each other
• Gases: Particles are far apart and move freely in all directions

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5. Change of State (Phase Transitions)

• Melting: Solid → Liquid (on heating)
• Freezing: Liquid → Solid (on cooling)
• Evaporation: Liquid → Gas (from surface)
• Boiling: Liquid → Gas (throughout the liquid)
• Condensation: Gas → Liquid (on cooling)
• Sublimation: Solid → Gas (directly, e.g., camphor)
• Deposition: Gas → Solid (directly, e.g., frost)

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6. Physical and Chemical Properties

• Physical Properties: Can be observed without changing identity (e.g., color, boiling point)
• Chemical Properties: Observed during a chemical change (e.g., flammability, rusting)

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7. Importance of Understanding Matter

• Helps in understanding everyday phenomena
• Used in industrial and scientific processes
• Crucial in designing and using materials in different fields

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8. Summary

• Matter exists in three primary states: solid, liquid, gas
• Particles have motion and interact with each other
• States of matter change due to heat and pressure
• Understanding matter helps in science, industry, and daily life

Evaporation – Short Notes (Class 9)

1. Definition

Evaporation is the process of slow conversion of a liquid into vapour from its surface, at any temperature below boiling point.

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2. Daily Life Example

Drying of wet clothes

Water from ponds and puddles disappearing

Sweat drying from skin

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3. Key Features

Happens only at the surface

Takes place at any temperature

Slow and natural process

Uses heat from surroundings

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4. Factors Affecting Evaporation

Temperature: Higher temp = faster evaporation

Surface Area: Larger area = more evaporation

Humidity: More humidity = slower evaporation

Wind Speed: More wind = faster evaporation

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5. Evaporation Causes Cooling

When a liquid evaporates, it takes heat from the surface, causing cooling.

Examples:

Sweat cools our body

Water stays cool in an earthen pot

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6. Importance in Daily Life

Cooling effect (sweating, matka)

Drying clothes

Making salt from seawater

Used in coolers and fridges (indirectly)

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Matter in Our Surroundings – Short Notes (Class 9)

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1. What is Matter?

Anything that has mass and occupies space

Found in all forms — solid, liquid, gas

2. Characteristics of Particles of Matter

Made up of tiny particles

Particles have space between them

Particles are constantly moving

Particles attract each other

3. States of Matter

Solid: Fixed shape and volume, tightly packed particles

Liquid: No fixed shape, fixed volume, flows easily

Gas: No fixed shape or volume, highly compressible, free-moving particles

4. Diffusion

Mixing of particles of two substances

Faster in gases than liquids

Example: Smell of perfume spreads in a room

5. Interconversion of States of Matter

Solid ↔ Liquid: Melting / Freezing

Liquid ↔ Gas: Evaporation / Condensation

Solid ↔ Gas: Sublimation / Deposition

These changes are physical and reversible

6. Melting Point

Temperature at which a solid changes to liquid

Melting point of ice = 0°C

7. Boiling Point

Temperature at which liquid changes to gas

Boiling point of water = 100°C

8. Latent Heat

Heat required to change the state without temperature change

Latent heat of fusion: Solid → Liquid

Latent heat of vaporisation: Liquid → Gas

9. Sublimation

Solid directly changes to gas without becoming liquid

Example: Camphor, naphthalene, dry ice

10. Evaporation

Slow change from liquid to gas at all temperatures below boiling point

Happens only at surface

Uses heat from surroundings

Factors affecting evaporation:

1. Temperature

2. Surface area

3. Humidity

4. Wind speed

Evaporation causes cooling

Example: Sweat cools the body, matka water stays cool

11. Condensation

Gas changes to liquid on cooling

Example: Water droplets on a cold glass

12. Freezing

Liquid changes to solid on cooling

Reverse of melting

Example: Water turns to ice in freezer

13. Effect of Pressure on Matter

Increasing pressure → Gases become liquids

Example: LPG and CNG cylinders are compressed gases

14. Plasma and Bose-Einstein Condensate (For Info Only)

Plasma: Ionized gas (found in stars, neon signs)

Bose-Einstein Condensate (BEC): Supercooled atoms behaving as a single unit

15. Important Temperatures

Melting point of ice: 0°C

Boiling point of water: 100°C

Room temperature: ~25°C

16. Summary (One-Liners for Revision)

Matter has mass and occupies space

Three main states: Solid, liquid, gas

Matter changes state due to heat or pressure

Evaporation causes cooling

Interconversion of states.

HOTS-Based MCQs – Matter in Our Surroundings

1. When dry ice is kept in open air, it disappears without forming any liquid. This is due to:

a) Evaporation

b) Sublimation

c) Boiling

d) Melting

2. Why do we feel cool when sweat evaporates from our body?

a) It absorbs heat from the sun

b) It releases heat into the air

c) It absorbs body heat during evaporation

d) It reacts with oxygen

3. If a gas is compressed in a closed container, what happens to its pressure and temperature (assuming no heat loss)?

a) Both increase

b) Pressure increases, temperature decreases

c) Both decrease

d) Pressure decreases, temperature increases

4. Why does a balloon burst when over-inflated?

a) Increase in kinetic energy

b) Increase in intermolecular space

c) Increase in air pressure

d) Decrease in temperature

5. A gas jar containing air is inverted over a gas jar containing bromine vapours. After some time, the upper jar also turns reddish-brown. What does this prove?

a) Bromine is heavier than air

b) Bromine reacts with air

c) Gases diffuse and mix

d) Air is reddish

6. Steam causes more severe burns than boiling water because:

a) Steam occupies more volume

b) Steam is hotter than water

c) Steam contains more dissolved oxygen

d) Steam has more latent heat

7. When perfume is sprayed in one corner of a room, its smell quickly spreads. This demonstrates:

a) Evaporation

b) Condensation

c) Diffusion

d) Boiling

8. In which of the following situations does water vaporise faster?

a) In a closed room

b) On a rainy day

c) On a windy and hot day

d) In a refrigerator

9. A solid substance directly converted into gas without melting. This is due to:

a) Low boiling point

b) Weak intermolecular forces

c) High humidity

d) Strong gravitational force

10. If you increase the pressure on a gas at constant temperature, its volume:

a) Increases

b) Decreases

c) Remains the same

d) Becomes zero

11. Which of the following helps in drying wet clothes faster?

a) High humidity

b) Still air

c) Low temperature

d) Large surface area

12. A substance X is rigid, incompressible and has a definite shape. Identify the state of matter:

a) Liquid

b) Gas

c) Solid

d) Plasma

13. Why is ice at 0°C more effective in cooling than water at 0°C?

a) Ice has less density

b) Ice absorbs latent heat during melting

c) Water evaporates faster

d) Water has higher surface tension

14. Which of the following does not affect the rate of evaporation?

a) Temperature

b) Wind speed

c) Humidity

d) Boiling point

15. What change will occur in boiling point of water if atmospheric pressure is decreased?

a) Boiling point increases

b) Boiling point decreases

c) Boiling point remains the same

d) Water doesn’t boil

16. Why are gases compressible but solids are not?

a) Gases are lighter

b) Gases have high kinetic energy and large intermolecular space

c) Solids have high temperature

d) Solids can flow

17. A liquid changes into vapour without boiling. This process is called:

a) Sublimation

b) Boiling

c) Evaporation

d) Fusion

18. Why does camphor disappear when kept open?

a) It melts

b) It dissolves in air

c) It evaporates

d) It sublimates

19. Which of the following statements is true for all matter?

a) All matter has fixed shape

b) All matter can be compressed

c) All matter is made up of particles

d) All matter diffuses at the same rate

20. Which process takes place when a gas changes into a liquid?

a) Evaporation

b) Condensation

c) Sublimation

d) Freezing

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Here are the answers to the 20 HOTS-based MCQs from Chapter: Matter in Our Surroundings (Class 9):

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1. b) Sublimation

2. c) It absorbs body heat during evaporation

3. a) Both increase

4. c) Increase in air pressure

5. c) Gases diffuse and mix

6. d) Steam has more latent heat

7. c) Diffusion

8. c) On a windy and hot day

9. b) Weak intermolecular forces

10. b) Decreases

11. d) Large surface area

12. c) Solid

13. b) Ice absorbs latent heat during melting

14. d) Boiling point

15. b) Boiling point decreases

16. b) Gases have high kinetic energy and large intermolecular space

17. c) Evaporation

18. d) It sublimates

19. c) All matter is made up of particles

20. b) Condensation

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