CBSE · CLASS 9 · Science
READY

Matter in Our Surroundings

Matter has mass and occupies space. This chapter explains particles, states of matter, change of state, latent heat and evaporation.

Learning Objectives

Why This Matters

Matter in Our Surroundings connects textbook science to daily life, experiments and exam understanding.

Concept Map

particle nature of matter solids liquids and gases change of state latent heat evaporation temperature and pressure

📖 Story Mode

A stone, water and air look different, but all occupy space and have mass.

Micro-Lessons

MICRO LESSON 1

What is Matter?

Picture it: A stone, water and air look different, but all occupy space and have mass.

Simple: Matter is anything that has mass and occupies space.

Example: Air in a balloon occupies space.
Remember: Mass + space = matter.
Quick Check: Is light matter?
MICRO LESSON 2

Particles of Matter

Picture it: A drop of ink spreads through water because matter is made of moving particles.

Simple: Matter is made of extremely small particles.

Example: Potassium permanganate colours a large volume of water.
Remember: Tiny particles can spread widely.
Quick Check: What does diffusion show?
MICRO LESSON 3

Space Between Particles

Picture it: Sugar disappears in water because its particles occupy spaces between water particles.

Simple: Particles of matter have spaces between them.

Example: Salt dissolves without greatly increasing water level.
Remember: Particles are not packed without gaps.
Quick Check: Why does sugar dissolve?
MICRO LESSON 4

Particles Keep Moving

Picture it: Perfume smell reaches another corner of a room.

Simple: Particles are continuously moving and move faster when heated.

Example: Hot food smell spreads faster than cold food smell.
Remember: More heat means faster motion.
Quick Check: Why is diffusion fast in gases?
MICRO LESSON 5

Force of Attraction

Picture it: A solid keeps shape because its particles strongly attract one another.

Simple: Attraction is strongest in solids and weakest in gases.

Example: A stone is rigid; air spreads freely.
Remember: Solid strong, liquid medium, gas weak.
Quick Check: Which state has weakest attraction?
MICRO LESSON 6

Three States of Matter

Picture it: Ice, water and steam are the same substance in different states.

Simple: Solids have fixed shape and volume; liquids fixed volume; gases neither.

Example: Book, milk and oxygen.
Remember: Solid fixes both, liquid one, gas none.
Quick Check: Why are gases compressible?
MICRO LESSON 7

Change of State

Picture it: Heating ice produces water and then steam.

Simple: Temperature or pressure can change the state of matter.

Example: Melting, boiling, freezing and condensation.
Remember: Heat loosens particle attraction.
Quick Check: What is gas to liquid called?
MICRO LESSON 8

Latent Heat

Picture it: Ice absorbs heat while melting but stays at 0°C until melting ends.

Simple: Latent heat changes state without changing temperature.

Example: Melting ice at 0°C.
Remember: Hidden heat changes state.
Quick Check: Why is temperature constant during melting?
MICRO LESSON 9

Evaporation

Picture it: Wet clothes dry even below boiling temperature.

Simple: Evaporation is surface conversion of liquid into vapour.

Example: Sweat evaporates and cools skin.
Remember: Evaporation happens at the surface.
Quick Check: How is evaporation different from boiling?
MICRO LESSON 10

Factors Affecting Evaporation

Picture it: Clothes dry faster on a hot windy day.

Simple: Evaporation increases with surface area, temperature and wind speed, and decreases with humidity.

Example: Spread-out clothes dry faster.
Remember: Hot, wide, windy, dry = faster.
Quick Check: Why do clothes dry slowly in humidity?

Worked Examples

Convert 25°C to Kelvin.

25 + 273 = 298 K.

Why does an earthen pot cool water?

Water evaporates through pores and absorbs heat from the pot and water.

MCQs

1. Most compressible state is:

2. Evaporation causes:

3. SI unit of temperature is:

4. Solid directly to gas is:

5. Evaporation is fastest when humidity is:

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