C - 1, Matter In Our Surroundings || Notes

🧪 Matter in Our Surroundings – Class 9 Notes

🔷 What is Matter?

Matter is anything that occupies space and has mass.

Examples: Clouds ☁️, Stars ✨, Plants 🌱, Animals 🐘, Stones 🪨

📚 Classification of Matter

🔹 Physical Classification

• 🧊 Solid
• 💧 Liquid
• 💨 Gas

🔸 Chemical Classification

• 🧪 Element
• 🧬 Compound
• 🥣 Mixture

🧬 Characteristics of Particles of Matter

• Have space between them: Solids < Liquids < Gases
• Are always moving: Higher temperature increases particle motion
• Attract each other: Strongest in solids, weakest in gases

🌡️ States of Matter

1. 🧊 Solid

• Definite shape and volume
• Rigid and incompressible
• Example: Ice, Pen, Brick

2. 💧 Liquid

• No definite shape, but definite volume
• Can flow and take shape of container
• Example: Water, Juice

3. 💨 Gas

• No definite shape or volume
• Highly compressible and has high fluidity
• Example: Air, LPG

🔄 Change of State of Matter

By:

• 🌡️ Changing Temperature
• 🧯 Changing Pressure

Temperature Changes

• Melting Point: Ice melts at 0°C or 273K
• Latent Heat of Fusion: Heat to convert solid → liquid at melting point
• Boiling Point: Water boils at 100°C
• Latent Heat of Vaporization: Heat to convert liquid → gas at boiling point
• Sublimation: Solid ⇌ Gas without liquid phase (e.g., Camphor, Iodine)

Pressure Changes

Gas can be liquefied by increasing pressure and reducing temperature.

Dry Ice: Solid CO₂ formed by cooling CO₂ under high pressure

🌬️ Evaporation

Definition: Conversion of liquid to vapour at temperatures below boiling point.

Factors Affecting Evaporation

Factor	Effect
🌍 Surface Area	Larger area = faster evaporation (e.g., tea in a saucer)
🌡️ Temperature	Higher temp = faster evaporation
💧 Humidity	More moisture = slower evaporation
💨 Wind Speed	Wind removes water vapour = faster evaporation

❄️ Cooling by Evaporation

Evaporation absorbs heat from surroundings → cooling effect

Example: Acetone on palm feels cold