Chapter Summary 📝

Key Points to Remember

About Matter

• ✅ Made up of small particles
• ✅ Exists in three states: Solid, Liquid, Gas

Forces of Attraction

State Changes

• Melting point of ice: 0°C = 273 K
• Boiling point of water: 100°C = 373 K
• States can be changed by temperature or pressure

Special Changes

• Sublimation: Solid → Gas (directly)
• Deposition: Gas → Solid (directly)

Evaporation

• Surface phenomenon (below boiling point)
• Causes cooling
• Depends on: surface area, temperature, humidity, wind

Latent Heat

• Latent heat of fusion: Energy to melt 1 kg solid
• Latent heat of vaporisation: Energy to vaporise 1 kg liquid

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Important Units 📏

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Practice Questions ❓

Short Answer

1. Convert to Celsius:

   • 293 K = 20°C (293 - 273)
   • 470 K = 197°C (470 - 273)

2. Convert to Kelvin:

   • 25°C = 298 K (25 + 273)
   • 373°C = 646 K (373 + 273)

3. Why do naphthalene balls disappear?

   They undergo sublimation — directly change from solid to gas.

4. Why can we smell perfume from metres away?

   Perfume particles diffuse rapidly through air due to kinetic energy.

5. Arrange in increasing order of forces of attraction:

   Oxygen < Water < Sugar

6. Physical state of water at:

   • 25°C → Liquid
   • 0°C → Solid/Liquid (melting point)
   • 100°C → Liquid/Gas (boiling point)

Reasoning Questions

1. Why is ice at 273 K more effective for cooling than water at 273 K?

   Ice absorbs latent heat of fusion while melting, providing extra cooling!

2. What produces more severe burns — boiling water or steam?

   Steam — it has extra latent heat of vaporisation!

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Quick Revision Diagram

STATES OF MATTER
       │
       ├── SOLID (rigid, fixed shape/volume)
       │      ↓ Melting (273 K for ice)
       ├── LIQUID (fluid, fixed volume)
       │      ↓ Boiling (373 K for water)
       └── GAS (compressible, fills container)

      SUBLIMATION: Solid ↔ Gas directly

You've completed Chapter 1! 🎉