Class 9 Science — Chapter 8: Atoms and Molecules
90 practice questions · 30 Easy · 30 Medium · 30 Hard
Practise Class 9 Science Chapter 8, "Atoms and Molecules", with 90 NCERT-aligned multiple-choice questions. The set is split into 30 Easy, 30 Medium and 30 Hard questions, so you can warm up on the fundamentals and then push into the exam-level problems that separate top scorers in CBSE Board exams and the JEE & NEET foundation years.
"Atoms and Molecules" is one of the chapters where concept clarity across physics, chemistry and biology basics really pays off. Each MCQ on this chapter is timed and uses exam-grade marking (+2 correct, −1 wrong, 0 skipped), training the same accuracy-under-pressure that real papers demand. Every question carries a short explanation, so a wrong answer becomes a quick lesson rather than a dead end — the fastest way to close gaps before a test.
Use this chapter as targeted revision: attempt the Easy set first to confirm your basics on Atoms and Molecules, then move to Medium and Hard to test application and problem-solving. Your accuracy, streaks and XP save automatically, and the chapter feeds into your overall Class 9 Science mastery score. A few sample questions are shown below; sign in free to practise all 90.
Key concepts: Atoms and Molecules (Class 9 Science)
This chapter explains force and inertia through Newton's three laws of motion, defines momentum, and applies the law of conservation of momentum.
- Force and inertia
- A force can change the speed, direction or shape of a body. Inertia is the tendency to resist a change in state of rest or motion, and depends on mass.
- Newton's first law
- A body stays at rest or in uniform motion unless acted on by an unbalanced (net) force — the law of inertia.
- Newton's second law
- The rate of change of momentum is proportional to the applied force; this gives F = ma.
- Newton's third law
- To every action there is an equal and opposite reaction; the two forces act on different bodies.
- Momentum
- The product of mass and velocity, p = mv; a vector with the same direction as velocity.
- Conservation of momentum
- In the absence of an external force, the total momentum of a system stays constant — the basis of recoil and collision problems.
Key formulas — Atoms and Molecules
💡 Exam tips for Atoms and Molecules
- Action and reaction act on different bodies, so they never cancel each other out.
- Always assign directions (signs) to velocities before applying conservation of momentum.
Sample questions
The atomic theory was proposed by:
John Dalton proposed the atomic theory in 1808.
Molecular mass of CO₂ (C = 12, O = 16) is:
12 + 2(16) = 12 + 32 = 44 u.
Number of atoms in 0.5 mole of carbon is:
0.5 × 6.022 × 10²³ = 3.011 × 10²³ atoms.
Atoms and Molecules — FAQs
What are the key concepts in Class 9 Science Atoms and Molecules?+
This chapter explains force and inertia through Newton's three laws of motion, defines momentum, and applies the law of conservation of momentum. Key ideas include Force and inertia, Newton's first law, Newton's second law, Newton's third law, Momentum.
What does Class 9 Science Chapter 8 (Atoms and Molecules) cover on XamBaaz?+
It covers 90 NCERT-aligned MCQs on "Atoms and Molecules" — 30 Easy, 30 Medium and 30 Hard — each with a timed quiz and an instant explanation, suitable for CBSE Board exams and the JEE & NEET foundation years.
Are these "Atoms and Molecules" questions free to practise?+
Yes — sign in with Google to practise "Atoms and Molecules" free. Full unlimited access is ₹999/year (limited-time launch price), with no per-chapter charges.
How should I revise "Atoms and Molecules" for the exam?+
Start with the Easy quiz to confirm your fundamentals, then attempt Medium and Hard for application-level practice. Review each explanation, retry the questions you miss, and track your accuracy on this chapter until it is consistently high.
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