Atomic Foundations of Matter — Class 9 Science NCERT Solutions (Free)
Free step-by-step NCERT solutions for Class 9 Science chapter "Atomic Foundations of Matter" — 8 important questions with detailed answers for CBSE board exam preparation.
TL;DR: Free step-by-step NCERT solutions for Class 9 Science chapter "Atomic Foundations of Matter" — 8 important questions with detailed answers for CBSE bo…
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Key Questions Covered:
- State and explain the Law of Conservation of Mass.
- State and explain the Law of Definite Proportions.
- Define atomic mass unit (u) and atomic mass.
- + 5 more questions in the full chapter
Solutions Summary:
| Question | Status |
|---|---|
| State and explain the Law of Conservation of Mass. | ✓ Solved |
| State and explain the Law of Definite Proportions. | ✓ Solved |
| Define atomic mass unit (u) and atomic mass. | ✓ Solved |
Showing 3 of 8 questions
Q1: State and explain the Law of Conservation of Mass.
Law of Conservation of Mass:
Mass cannot be created or destroyed in a chemical reaction; mass of reactants = mass of products.
Explanation: In chemical reaction, bonds break and reform between atoms. Atoms rearrange but total number of each type of atom remains same, so total mass remains constant.
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Q2: State and explain the Law of Definite Proportions.
Law of Definite Proportions (Law of Constant Composition):
A compound always contains the same elements in the same proportion by mass, regardless of source or method of preparation.
Example: Water always contains H and O in ratio 1:8 by mass
2 g H : 16 g O in any water sample (H₂O)
Explanation: A c...
Q3: Define atomic mass unit (u) and atomic mass.
Atomic mass unit (u or amu):
Standard unit for measuring mass of atoms and molecules.
1 u = 1/12 of mass of one carbon-12 atom = 1.66 × 10⁻²⁷ kg
Atomic mass = Average relative mass of atom of an element compared to 1/12 of C-12
Example: Atomic mass of Hydrogen ≈ 1 u, Carbon = 12 u, Oxygen = 16 u
Mol...
Showing 3 of 8 questions. Visit the full page for complete solutions.