Chapter 7: Particulate Nature of Matter — Class 8 Science

🧭 Chapter Overview – Particulate Nature of Matter

The chapter “Particulate Nature of Matter” explores the fundamental concept that all matter—everything around us—is made up of extremely small particles. These particles are invisible to the naked eye but are the building blocks of all substances. Through interesting classroom activities and real-life examples, students learn how the behavior, spacing, and motion of these particles determine the three physical states of matter—solids, liquids, and gases.

This chapter also introduces ancient ideas like Acharya Kanad’s Parmanu theory, and modern explanations involving interparticle attraction and thermal energy. Learners understand how changes in heat can cause changes in state—from solid to liquid and liquid to gas—and how the properties of each state depend on the strength of these invisible forces.

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🔍 1. What Is Matter Made Of?

• All matter (anything that has mass and occupies space) is made up of very tiny particles called constituent particles.
• These particles are so small that they cannot be seen even with a microscope.

Activities & Observations

• Chalk Activity: Breaking chalk repeatedly — it remains chalk even when powdered → physical change, not chemical.
• Sugar in Water Activity: Sugar disappears but tastes sweet → sugar breaks into smaller particles and occupies spaces between water particles (interparticle spaces).

Conclusion

• Matter consists of extremely small particles.
• These particles have spaces between them and are held together by attractive forces.

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⚛️ 2. What Decides the States of Matter?

(a) Interparticle Attraction

• Force of attraction between particles is called interparticle attraction.
• Strength of this force depends on distance between particles.
  • Smaller distance → stronger attraction.

(b) States of Matter

Matter exists in three physical states: Solid, Liquid, Gas.

🧱 3. Solid State

Property	Explanation
Shape & Volume	Definite shape and volume
Particle Arrangement	Very tightly packed
Interparticle Attraction	Very strong
Movement	Only vibrate about fixed positions
Melting Point	Temperature at which solid changes into liquid

Examples:

Substance	Melting Point
Ice	0 °C
Urea	133 °C
Iron	1538 °C

Note: Ice is an exception — its solid form has particles farther apart than in liquid water.

💧 4. Liquid State

Property	Explanation
Shape	No fixed shape – takes the shape of container
Volume	Fixed volume
Particle Arrangement	Loosely packed compared to solids
Movement	Move freely but within limited space
Interparticle Attraction	Weaker than solids

Activity: Water poured into containers of different shapes always measures 200 mL → definite volume, variable shape.

Boiling & Evaporation

• Boiling Point: Temperature where liquid → vapour.
• Evaporation: Slow vaporisation from surface, even below boiling point.

🌬️ 5. Gaseous State

Property	Explanation
Shape	No fixed shape
Volume	No fixed volume – fills entire space available
Particle Arrangement	Very far apart
Interparticle Attraction	Negligible
Movement	Free and fast in all directions

Activity: Smoke from incense stick spreads in another jar → gas particles move freely and occupy all available space.

🧩 6. Interparticle Spacing

(a) Solids

• Particles closely packed; minimal spaces.
• Not compressible.

(b) Liquids

• Particles less tightly packed; have small spaces.
• Almost incompressible.

(c) Gases

• Particles far apart; have large spaces.
• Highly compressible.

Activity:

• Syringe with air → easy to compress (gas compressible).
• Syringe with water → hard to compress (liquid incompressible).

🍬 7. Dissolution and Interparticle Spaces

• When sugar dissolves in water, particles of sugar occupy the spaces between water particles → level slightly decreases.
• Sand does not dissolve because water particles cannot pull sand particles apart → sand settles down.

💨 8. Motion of Particles

In Liquids

• Potassium permanganate in water: colour spreads evenly → water particles move and help solute spread.

In Gases

• Incense stick in room: fragrance spreads → gas particles move freely in all directions.

Faster Motion with Heat:

• Hot water spreads colour faster than cold water → heating increases particle motion.

🧼 9. Application of Particle Nature

• Soap cleansing: Soap particles surround oil; one end sticks to oil, the other mixes with water → helps remove grease.

🔬 10. Key Concepts Summary Table

Property	Solid	Liquid	Gas
Interparticle spacing	Minimum	More than solids	Maximum
Arrangement	Closely packed	Loosely packed	Free
Interparticle attraction	Strong	Moderate	Very weak/negligible
Shape	Fixed	No fixed shape	No fixed shape
Volume	Fixed	Fixed	No fixed volume
Motion of particles	Vibrations only	Move within limited space	Move freely in all directions
Compressibility	Negligible	Almost none	High
Example	Ice, Iron	Water, Milk	Air, Oxygen

🧠 11. Concept Connections

• Acharya Kanad: Ancient Indian philosopher who introduced idea of Parmanu (atom) — indivisible eternal particles.
• Thermal Energy Effect:
  • Heating → increases motion → weakens attractions → solid → liquid → gas.
  • Cooling → decreases motion → strengthens attractions → gas → liquid → solid.

🧾 12. Snapshots / Quick Revision

✅ Matter is made of extremely small particles.
✅ Particles have spaces and are held by attractive forces.
✅ Strength of these forces varies in solids, liquids, and gases.
✅ Solids → strongest attraction, fixed shape.
✅ Liquids → weaker attraction, fixed volume, no fixed shape.
✅ Gases → negligible attraction, no fixed shape or volume.
✅ Heat energy increases particle movement.
✅ Interparticle spaces allow dissolution and diffusion.

💡 13. Extra Thinking

Why do gases mix easily but solids don’t?
→ Gas particles are far apart and move freely, so they mix quickly. Solid particles are fixed in place.

Why does sea water taste salty?
→ Because salt particles are dissolved and occupy spaces between water molecules, though invisible.

Are grains of rice and rice flour solids or liquids?
→ They are solids — they only appear to flow because their small solid grains slide past each other.

🧠 Conclusion – Particulate Nature of Matter

In conclusion, the Particulate Nature of Matter helps us understand that all substances are made up of particles that are constantly in motion and have spaces between them. The degree of motion and attraction among these particles defines whether a substance exists as a solid, liquid, or gas. By studying these properties, students can better grasp everyday phenomena—like dissolving sugar, melting ice, or the fragrance of incense spreading through the air.

This concept lays the foundation for future topics like atoms, molecules, and chemical reactions. It shows that the invisible world of particles is the key to understanding the visible world around us.

🔗 Explore more detailed chapter notes, visuals, and printable PDFs only on a2zly.com — where science meets simplicity.

🔗 INTERNAL & EXTERNAL LINKS

Internal Links (A2ZLY):

• Chapter 8 – Nature of Matter: Elements, Compounds, and Mixtures Notes 2025
• Class 8 Science All Chapters Notes 2025
• NEP 2025 Study Material Hub | A2ZLY

External Links:

• NCERT Official Website
• CBSE Curriculum 2025–26
• UNESCO Learning Portal

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