Class 9 Science – Chapter: Matter in Our Surroundings
🔹 Introduction to Matter
Matter is anything that has mass and occupies space.
Examples: Air, water, iron, sand.
🔿 Characteristics of Matter
Made up of tiny particles.
Particles have space between them.
Particles are constantly moving.
Particles attract each other.
📈 States of Matter
| State | Shape | Volume | Compressibility | Flow |
|---|---|---|---|---|
| Solid | Fixed | Fixed | Negligible | Does not flow |
| Liquid | Not fixed | Fixed | Very less | Flows easily |
| Gas | Not fixed | Not fixed | High | Flows freely |
Examples
Solid: Ice, wood
Liquid: Water, oil
Gas: Oxygen, carbon dioxide
🔹 Properties of Particles of Matter
1. Particles are very small
Cannot be seen by naked eye.
2. Particles have spaces between them
The space is maximum in gases, minimum in solids.
3. Particles are constantly moving
Movement increases with temperature.
4. Particles attract each other
Strongest in solids, weakest in gases.
🔹 Diffusion
Definition: The intermixing of particles of two different types of matter on their own.
Faster in gases, slower in liquids, very slow in solids.
Example: Smell of perfume spreads in a room.
🔹 Change of State of Matter
Matter can change from one state to another by changing temperature or pressure.
📈 Important Terms
| Term | Definition |
|---|---|
| Melting | Solid → Liquid (on heating) |
| Freezing | Liquid → Solid (on cooling) |
| Boiling | Liquid → Gas (at boiling point) |
| Condensation | Gas → Liquid (on cooling) |
| Sublimation | Solid → Gas directly (without liquid stage) |
Examples of Sublimation
Camphor, iodine, ammonium chloride.
🔹 Evaporation
Definition: The phenomenon of change of a liquid into vapour at any temperature below its boiling point.
Factors Affecting Evaporation
Surface area (increases evaporation)
Temperature (higher temperature, faster evaporation)
Humidity (more humidity, slower evaporation)
Wind speed (higher speed, faster evaporation)
Applications of Evaporation
Cooling of water in earthen pots.
Sweat evaporates to cool our body.
🔹 Latent Heat
| Type | Description |
|---|---|
| Latent heat of fusion | Heat energy required to change 1kg solid to liquid without temperature change. |
| Latent heat of vaporization | Heat energy required to change 1kg liquid to gas without temperature change. |
Example: Ice melts to water at 0°C by absorbing latent heat of fusion.
🔹 States of Matter: Beyond Solid, Liquid, and Gas
Plasma
Fourth state of matter.
Ionized gases (high energy particles).
Found in stars and fluorescent lights.
Bose-Einstein Condensate (BEC)
Fifth state of matter.
Formed at temperatures close to absolute zero (-273°C).
Extremely low-energy particles behaving as one.
🔹 Summary Table
| Property | Solid | Liquid | Gas |
|---|---|---|---|
| Shape | Definite | Not definite | Not definite |
| Volume | Fixed | Fixed | Not fixed |
| Compressibility | Very less | Slightly | High |
| Kinetic energy | Low | Moderate | High |
| Forces of attraction | Strong | Moderate | Weak |
📌 Key Points to Remember
Matter can exist in different states depending on temperature and pressure.
Energy plays a vital role in the change of state.
Evaporation causes cooling.
Sublimation is a direct change from solid to gas.