Chapter 5: Physical States of Matter

Physical States of Matter explains the basic forms in which matter exists — solid, liquid, and gas — along with their properties, behavior, and changes of state. These Class 9 Chemistry Chapter 5 MCQs are designed to help students test their knowledge on key concepts such as intermolecular forces, kinetic theory, diffusion, evaporation, and the effect of temperature and pressure on different states of matter.

1. Which of the following is a characteristic property of solids?

  • A. Definite shape and volume ✅
  • B. Definite volume but no definite shape
  • C. No definite shape and volume
  • D. Easily compressible
Explanation: Solids have fixed shapes and volumes due to strong intermolecular forces.

2. Which state of matter has the weakest intermolecular forces?

  • A. Solid
  • B. Liquid
  • C. Gas ✅
  • D. Plasma
Explanation: In gases, particles are far apart and have negligible intermolecular forces.

3. The process of a solid changing directly into a gas is called:

  • A. Condensation
  • B. Evaporation
  • C. Sublimation ✅
  • D. Melting
Explanation: Sublimation is when solids change directly into gases without passing through the liquid state.

4. Which factor increases the rate of evaporation?

  • A. Low temperature
  • B. High temperature ✅
  • C. Low surface area
  • D. High humidity
Explanation: Higher temperatures increase the kinetic energy of particles, speeding up evaporation.

5. The random motion of gas particles is explained by:

  • A. Law of Conservation of Mass
  • B. Dalton’s Atomic Theory
  • C. Kinetic Molecular Theory ✅
  • D. Avogadro’s Law
Explanation: The Kinetic Molecular Theory describes particle motion and energy in gases.

6. What happens to gas pressure if temperature increases at constant volume?

  • A. It decreases
  • B. It increases ✅
  • C. It remains the same
  • D. It becomes zero
Explanation: At constant volume, increasing temperature increases particle speed, leading to more collisions and higher pressure.

7. Which state of matter is nearly incompressible?

  • A. Gas
  • B. Liquid ✅
  • C. Plasma
  • D. Vapor
Explanation: Liquids are nearly incompressible due to closely packed particles.

8. The diffusion of a gas is faster when:

  • A. The gas is heavy
  • B. The gas is light ✅
  • C. Temperature is low
  • D. Pressure is high
Explanation: Lighter gases move faster and diffuse more quickly than heavier gases.

9. Which change of state is involved when water vapor turns into liquid water?

  • A. Condensation ✅
  • B. Evaporation
  • C. Melting
  • D. Freezing
Explanation: Condensation is the process where gas changes into liquid.

10. The boiling point of a liquid is affected by:

  • A. Shape of the container
  • B. Color of the liquid
  • C. External pressure ✅
  • D. Type of thermometer
Explanation: Higher external pressure increases boiling point; lower pressure decreases it.

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