Chapter Exam

Chapter-7 Particulate Nature of Matter — Online MCQ Test

Q: What is the smallest unit of matter that retains the properties of an element?

Answer: B. Atom — An atom is the smallest unit of an element that retains all the chemical properties of that element.

Q: Which of the following best describes a molecule?

Answer: B. Two or more atoms bonded together — A molecule is formed when two or more atoms combine together through chemical bonds.

Q: In which state of matter are particles packed most closely together?

Answer: C. Solid — In solids, particles are tightly packed with minimal intermolecular spaces, giving them a fixed shape and volume.

Q: What is the process by which a solid directly converts into a gas without passing through the liquid state?

Answer: C. Sublimation — Sublimation is the direct phase transition from solid to gas, as seen in dry ice and naphthalene.

Q: Compare the intermolecular spaces in the three states of matter. Which arrangement is correct?

Answer: B. Gas > Liquid > Solid — Gases have the largest intermolecular spaces, followed by liquids, with solids having the smallest spaces between particles.

SCIENCE (CURIOSITY) · CLASS 8th · Karnataka State Board

Practice Chapter-7 Particulate Nature of Matter with a free chapter-wise online MCQ test for Karnataka State Board CLASS 8th SCIENCE (CURIOSITY). This chapter covers: atoms - molecules - states of matter - intermolecular force - intermolecular space - sublimation. AI-generated questions from basic to board-exam level, with instant results and explanations.

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Chapter-7 Particulate Nature of Matter — Important Questions & Answers (FAQ)

Frequently asked questions from Karnataka State Board CLASS 8th SCIENCE (CURIOSITY) — Chapter-7 Particulate Nature of Matter, with answers and explanations. These are sample questions; the exam has its own separate question set.

What is the smallest unit of matter that retains the properties of an element?

A. Molecule
B. Atom ✓
C. Electron
D. Compound

Answer: B. Atom
An atom is the smallest unit of an element that retains all the chemical properties of that element.

Which of the following best describes a molecule?

A. A single atom of any element
B. Two or more atoms bonded together ✓
C. A charged particle
D. The nucleus of an atom

Answer: B. Two or more atoms bonded together
A molecule is formed when two or more atoms combine together through chemical bonds.

In which state of matter are particles packed most closely together?

A. Gas
B. Liquid
C. Solid ✓
D. Plasma

Answer: C. Solid
In solids, particles are tightly packed with minimal intermolecular spaces, giving them a fixed shape and volume.

What is the process by which a solid directly converts into a gas without passing through the liquid state?

A. Melting
B. Vaporization
C. Sublimation ✓
D. Condensation

Answer: C. Sublimation
Sublimation is the direct phase transition from solid to gas, as seen in dry ice and naphthalene.

Why do gases exert pressure on the walls of a container?

A. Because gas particles are stationary
B. Because gas particles move rapidly and collide with the walls ✓
C. Because gases are denser than liquids
D. Because gas particles stick to the walls

Answer: B. Because gas particles move rapidly and collide with the walls
Gas particles move randomly at high speed and continuously collide with container walls, creating pressure.

Which of the following correctly explains why a liquid can flow but a solid cannot?

A. Liquids have stronger intermolecular forces than solids
B. Solids have larger intermolecular spaces than liquids
C. In liquids, particles can move over each other due to weaker intermolecular forces and larger spaces ✓
D. Solids have no intermolecular forces

Answer: C. In liquids, particles can move over each other due to weaker intermolecular forces and larger spaces
Liquids have weaker intermolecular forces and greater intermolecular spaces compared to solids, allowing particles to move and flow.

Compare the intermolecular spaces in the three states of matter. Which arrangement is correct?

A. Solid > Liquid > Gas
B. Gas > Liquid > Solid ✓
C. Liquid > Solid > Gas
D. All states have equal spaces

Answer: B. Gas > Liquid > Solid
Gases have the largest intermolecular spaces, followed by liquids, with solids having the smallest spaces between particles.

A substance changes from solid to liquid at 60°C and from liquid to gas at 100°C. At 50°C and normal pressure, what can be concluded about intermolecular forces?

A. Intermolecular forces are zero
B. Intermolecular forces are strong enough to keep particles in solid state ✓
C. Intermolecular forces are weak
D. Intermolecular forces are impossible to determine

Answer: B. Intermolecular forces are strong enough to keep particles in solid state
Since the substance is solid at 50°C (below melting point), intermolecular forces are strong enough to maintain the solid structure at this temperature.

A solid compound has a sublimation point below room temperature but hasn't sublimed in a closed container. The most logical reason is:

A. The sublimation point is incorrect
B. Sublimation has reached equilibrium; vapor pressure equals atmospheric pressure ✓
C. The compound is no longer solid
D. Sublimation cannot occur in containers

Answer: B. Sublimation has reached equilibrium; vapor pressure equals atmospheric pressure
In a closed container, subliming particles accumulate as vapor until equilibrium is reached where vapor pressure equals the rate of sublimation.

Consider three substances with melting points 100°C, 500°C, and -50°C respectively. At 25°C, which substance would have the strongest intermolecular forces and why?

A. 100°C substance because it's closest to room temperature
B. 500°C substance because it requires the most energy to overcome intermolecular forces and melt ✓
C. -50°C substance because it's already in liquid state
D. Cannot determine without knowing composition

Answer: B. 500°C substance because it requires the most energy to overcome intermolecular forces and melt
The substance with the highest melting point (500°C) requires the most thermal energy to break intermolecular forces, indicating the strongest intermolecular attractions.