Question Paper
Class / Subject: Class 9 (CBSE) · Science
Chapter: Chapter 3 — Chapter 3: Atoms and Molecules
Time Allowed: 15 minutes
Max Marks: 6
1. The Law of Conservation of Mass states mass is: [1]
(A) neither created nor destroyed
(B) always increasing
(C) always decreasing
(D) created during reactions
2. The Law of Constant Proportions was proposed by: [1]
(A) Joseph Proust
(B) Antoine Lavoisier
(C) John Dalton
(D) Isaac Newton
3. Water always contains hydrogen and oxygen in a fixed mass ratio of: [1]
(A) 1:8
(B) 8:1
(C) 1:1
(D) 2:1
4. A molecule is formed when: [1]
(A) two or more atoms combine chemically
(B) an atom splits into pieces
(C) an atom loses its nucleus
(D) protons are removed from an atom
5. The molecular mass of water (H₂O) is: [1]
(A) 18u
(B) 16u
(C) 2u
(D) 34u
6. Avogadro's number represents: [1]
(A) the number of particles in one mole of a substance
(B) the atomic mass of oxygen
(C) the number of protons in an atom
(D) the mass of one electron