Question 3
Which postulate of Dalton's atomic theory is the result of the law of conservation of mass?
One of the postulates of Dalton's atomic theory states that : 'Atoms cannot be created nor be destroyed in a chemical reaction'. This law is the result of law of conservation of mass.
Key Concepts Covered
This question tests your understanding of the following concepts from the chapter Atoms and Molecules: Question, Postulate, Dalton's, Atomic, Theory, Result. These are fundamental topics in Science that students are expected to master as part of the CBSE Class 9 curriculum.
A thorough understanding of these concepts will help you answer similar questions confidently in your CBSE examinations. These topics are frequently tested in both objective and subjective sections of Science papers. We recommend revising the relevant section of your textbook alongside practising these solved examples to build a strong foundation.
How to Approach This Question
Read the question carefully and identify what is being asked. Break down complex questions into smaller parts. Use the terminology and concepts discussed in this chapter. Structure your answer logically — begin with a definition or key statement, then provide supporting details. Review your answer to ensure it addresses all parts of the question completely.
Key Points to Remember
- Read the question carefully and identify all parts before answering.
- Use the terminology specific to this subject and chapter.
- Review the textbook content for this chapter before attempting questions.
- Practice writing concise, well-structured answers within time limits.
Practice more questions from Atoms and Molecules — Science, Class 9 CBSE
Chapter 3: Atoms and Molecules — Quick Reference
Quick Revision Points
- Law of conservation of mass: total mass unchanged in a reaction
- Law of constant proportions: elements in fixed mass ratio in a compound
- 1 u = 1/12 mass of C-12 = 1.66 × 10⁻²⁴ g
- Molecular mass = sum of atomic masses of all atoms in molecule
- 1 mole = 6.022 × 10²³ particles (Avogadro's number)
- Moles = mass / molar mass; Particles = moles × Nₐ
- Criss-cross method for writing chemical formulae using valencies
- Polyatomic ions: NH₄⁺, OH⁻, SO₄²⁻, NO₃⁻, CO₃²⁻, PO₄³⁻
- Read the detailed chapter notes for complete coverage of all NCERT topics.
- Practice all NCERT in-text and back exercise questions — they are frequently asked in exams.
- Focus on comparison tables, diagrams, and definitions — these are high-scoring areas.
- For numericals (if applicable), practice at least 20 problems of varying difficulty.
- Refer to the practice question bank (200+ questions) for thorough preparation.
- Detailed Notes: ch03-atoms-and-molecules.html
- Practice Questions: 100+ questions with answers in 05-practice-questions/
- Chapter Test: 30-mark test paper in 06-tests/chapter-tests-30marks/
- Formula Sheet: Complete formula reference in 03-teacher-aid/formula-sheet.html