Particulate Nature of Matter
1. What is Matter Made Of?
- Matter is made up of very small particles.
- These particles are called constituent particles.
- These cannot be seen with the naked eye or even an ordinary microscope.
- Example: Chalk powder is made of tiny particles of chalk.
Activities:
- Grinding chalk only breaks it into smaller pieces. It’s a physical change, not a chemical one.
- When sugar is dissolved in water, it breaks into tiny particles and spreads throughout the water – it disappears but still tastes sweet.
Key Terms:
- Interparticle spaces – Small spaces between the particles of matter.
- Constituent particles – Smallest units of any substance (like chalk, sugar).
2. What Decides Different States of Matter?
- Particles are held together by interparticle forces of attraction.
- The amount of attraction and the space between particles decide the state of matter: Solid, Liquid, or Gas.
2.1 Solid State
- Particles are tightly packed.
- Very strong interparticle attraction.
- Particles vibrate but do not move freely.
- Solids have fixed shape and fixed volume.
- When heated, particles vibrate more and the solid can melt into a liquid.
Melting Point: The temperature at which a solid turns into a liquid.
| Solid | Melting Point |
|---|---|
| Ice | 0°C |
| Urea | 133°C |
| Iron | 1538°C |
2.2 Liquid State
- Particles are less tightly packed than in solids.
- Weaker attraction between particles.
- Can move around, so liquids have no fixed shape.
- Liquids take the shape of the container but have a fixed volume.
- On heating, liquids boil and become gases.
Boiling Point: Temperature at which a liquid becomes a gas.
Evaporation: Slow process where liquid turns into vapour at any temperature.
2.3 Gaseous State
- Particles are very far apart and move freely in all directions.
- Very weak or no attraction between particles.
- Gases have no fixed shape or volume.
- They fill the entire space of the container.
3. Interparticle Spacing in All States
| Property | Solid | Liquid | Gas |
|---|---|---|---|
| Particle Spacing | Very close | A bit apart | Very far apart |
| Force of Attraction | Strongest | Moderate | Very weak |
| Movement | Only vibration | Can move slightly | Move freely |
| Shape | Fixed | Not fixed | Not fixed |
| Volume | Fixed | Fixed | Not fixed |
Example Activity:
- Pushing air in a syringe – it compresses, showing gases have more space.
- Mixing sugar in water – sugar particles fill the spaces between water particles.
4. Movement of Particles
- Particles in solids vibrate.
- In liquids, they move slowly.
- In gases, they move quickly in all directions.
Examples:
- Potassium permanganate in water spreads due to particle movement.
- Fragrance of incense sticks spreads in a room because air particles move and carry the smell.
Real-Life Example: Soap and Cleaning
- Soap particles surround oil stains.
- One end of the soap particle sticks to the oil, the other to water.
- This helps wash away oil and dirt.
Important Concepts to Remember
1. Matter is made of tiny particles.
2. These particles have spaces between them (interparticle space).
3. They attract each other with varying force.
4. Their movement and attraction decide if the matter is solid, liquid, or gas.
5. Solids – fixed shape and volume, strong attraction.
6. Liquids – no fixed shape, fixed volume, moderate attraction.
7. Gases – no fixed shape or volume, very weak attraction.
Snapshots (Quick Revision)
1. Matter = Small particles
2. Solid = Strong attraction, fixed shape and volume
3. Liquid = Medium attraction, fixed volume, no fixed shape
4. Gas = Weak attraction, no fixed shape or volume
5. Heating gives energy → particles move more → changes state
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