Complete Chemistry notes on matter and its state for BPSC and Other Competitive Exams in 2025
General Science- 7 (Chemistry)
Matter and its State
Matter
- Definition: Matter is anything that has mass and occupies space.
- It exists in various forms such as solid, liquid, and gas.
- Composed of atoms and molecules.
Physical Nature of Matter
- Matter is made of tiny particles.
- These particles are in constant motion (kinetic energy).
- Particles attract each other, and this force varies with state.
Characteristics of Particles of Matter
- Extremely small in size.
- Have inter-particle spaces (spaces between particles).
- Always in motion (possess kinetic energy).
- Possess inter-particle forces of attraction.
States of Matter
| State | Shape | Volume | Compressibility | Flow | Inter-particle Force | Particle Movement |
| Solid | Fixed | Fixed | Very Low | No | Strong | Vibrate at fixed positions |
| Liquid | Not fixed | Fixed | Low | Yes | Moderate | Freely move |
| Gas | Not fixed | Not fixed | High | Yes | Weak | Very fast movement |
Other States of Matter
- Plasma: Superheated ionized gas (e.g., Sun, lightning).
- Bose-Einstein Condensate (BEC): Formed at near absolute zero temperature. Particles behave as a single quantum entity.
Interconversion of States of Matter
Physical changes between states due to temperature or pressure:
| Process | Change |
| Melting | Solid → Liquid |
| Freezing | Liquid → Solid |
| Vaporization | Liquid → Gas |
| Condensation | Gas → Liquid |
| Sublimation | Solid ↔ Gas |
- Examples of Sublimation: Camphor, Iodine, Naphthalene
- Latent Heat: Heat absorbed or released during state change without a change in temperature.
Effect of Temperature and Pressure
- Increase in temperature → increases kinetic energy → leads to state change.
- Increase in pressure → compresses gas → can turn into liquid (e.g., LPG in cylinders).
Evaporation
- Conversion of liquid to vapor at its surface below the boiling point.
- Factors affecting evaporation:
- Surface area
- Temperature
- Humidity
- Wind speed
- Cooling Effect: Evaporation of sweat cools the body.
Key Terms to Remember
- Matter = Mass + Volume
- Inter-particle space: Maximum in gases, minimum in solids
- Latent Heat of Fusion: Heat required to change solid → liquid
- Latent Heat of Vaporization: Heat required to change liquid → gas
- Kinetic Energy: Energy possessed by particles due to motion
Few Important Facts– Matter and its state
- Sublimation: Camphor, Naphthalene, Iodine
- Highest Kinetic Energy: Gas
- Evaporation Factors: Temperature ↑, Surface area ↑, Humidity ↓
- BEC Predicted By: Satyendra Nath Bose and Albert Einstein
Matter and Its States – Quiz for Practice
1. Which of the following statements best describes a solid?
- ☐ It has a definite volume but no definite shape.
- ☐ It has neither a definite shape nor a definite volume.
- ☐ Its particles are far apart and move randomly and rapidly.
- ✅ It has a definite shape and a definite volume.
Rationale: Solids maintain shape and volume due to strong intermolecular forces and closely packed particles.
2. Which of the following is an example of a chemical compound?
- ☐ Air
- ☐ Gold (Au)
- ✅ Water (H₂O)
- ☐ Saltwater
Rationale: Water is a compound formed by hydrogen and oxygen in a fixed ratio, resulting in new properties.
3. A substance that cannot be broken down into simpler substances by ordinary chemical means is called a:
- ☐ Compound
- ☐ Mixture
- ✅ Element
- ☐ Solution
Rationale: Elements are pure substances consisting of only one type of atom.
4. Which of the following is a characteristic of a heterogeneous mixture?
- ☐ Components are chemically bonded.
- ☐ It has a uniform composition.
- ✅ Components retain their individual properties.
- ☐ Can be separated only chemically.
Rationale: Heterogeneous mixtures are not uniform and components remain physically distinct.
5. When ice melts into water, what state change occurs?
- ☐ Solid to Gas
- ☐ Liquid to Solid
- ✅ Solid to Liquid
- ☐ Liquid to Gas
Rationale: Melting is the process where a solid becomes a liquid due to heat.
6. Which of these is a homogeneous mixture?
- ☐ Sand and water
- ☐ Oil and water
- ✅ Sugar dissolved in water
- ☐ Iron filings and sulfur
Rationale: Sugar completely dissolves in water forming a uniform solution.
7. In which state of matter are particles most closely packed and have the least kinetic energy?
- ☐ Liquid
- ☐ Gas
- ✅ Solid
- ☐ Plasma
Rationale: Solids have tightly packed particles with minimal motion.
8. Which of the following describes the formation of a compound?
- ☐ Physical mixing of substances
- ☐ Elements broken down
- ✅ Chemical combination of elements in fixed ratio
- ☐ Change in physical state
Rationale: Compounds result from chemical bonding of elements in set proportions.
9. Oxygen (O₂) is an example of a:
- ☐ Compound
- ☐ Homogeneous mixture
- ✅ Element
- ☐ Heterogeneous mixture
Rationale: Oxygen is a pure element with identical atoms.
10. Which physical process involves a liquid turning into a gas?
- ☐ Condensation
- ☐ Melting
- ☐ Sublimation
- ✅ Evaporation
Rationale: Evaporation is the process of a liquid becoming vapor, especially below boiling point.
