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Access comprehensive study materials and useful resources for Chapter 03 Atoms and Molecules using the CBSE Class 9 Science Atoms and Molecules Exam Notes. Designed to align with the 2026-27 CBSE academic guidelines, these advanced resources help Class 9 Science students reinforce core concepts beyond standard textbooks.
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CBSE Class 9 Science Atoms and Molecules Exam Notes. Please refer to the examination notes which you can use for preparing and revising for exams. These notes will help you to revise the concepts quickly and get good marks.
Introduction
Matter is called ‘padarth’ in Hindi. Kanad was one of the first persons to propose that matter (or padarth) is made
up of very small particles called ‘parmanu’. John Dalton called these particles by the name of atom. The word
‘atom’ means ‘indivisible’ something which cannot be divided further. The particles of matter (atoms or parmanu)
normally exist in a combined form. This combined form of atoms is now called ‘molecules’. All matter is made up of
small particles called atoms and molecules. Different kinds of atoms and molecules have different properties due to
which different kinds of matter also show different properties.
Laws of Chemical Combination
The laws of chemical combination played a significant role in the development of Dalton’s atomic theory of matter.
There are two important laws of chemical combination.
(A) Law of conservation of mass
* Law of conservation of mass was given by Lavoisier in 1774. According to the law of conservation of mass :
Matter is neither created nor destroyed in a chemical reaction. The substances which combine together in a
chemical reaction are known as ‘reactants’ whereas the new substances formed as a result of chemical reaction
are called ‘products’. The law of conservation of mass means that in a chemical reaction, the total mass of products
is equal to the total mass of reactants. There is no change in mass during a chemical reaction.
Ex. Lavoisier showed that when mercuric oxide was heated, it produced free mercury and oxygen. The sum of masses of mercury and oxygen was found to be equal to the mass of mercuric oxide
Mercuric oxide = Mercury + Oxygen
100 g 92.6 g 7.4 g
Sol. Mass of the reactant = 100 g
Mass of the products = 92.6 + 7.4 g = 100.0 g
= 100 g
Since the total mass of the products formed is equal to the total mass of the reactants undergoing reaction, so the data is in agreement with low of conservation of mass.
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Science Class 9 Exam Resources: Chapter 03 Atoms and Molecules
Comprehensive Study Resources for Chapter 03 Atoms and Molecules
Explore essential learning tools for Class 9 Science Chapter 03 Atoms and Molecules. This curated collection features in-depth notes and targeted practice questions built around the active 2026 curriculum to streamline your daily revision.
Understanding Marking Schemes
Built using official NCERT guidelines for Class 9 Science, these materials provide reliable academic support. Integrating past examination questions and step-by-step solutions helps students understand official CBSE grading criteria.
Complete Revision for Science
For peak performance in upcoming evaluations, integrate official Science sample papers directly into your study schedule. Follow up your revision by attempting online MCQ tests for Chapter 03 Atoms and Molecules to refine calculation speed and precision.
FAQs
Our advanced study package for Chapter 03 Atoms and Molecules includes detailed concepts, diagrams, Mind Maps, and explanation of complex topics to ensure Class 9 students learn as per syllabus for 2026 exams.
The Mind Maps provided for Chapter 03 Atoms and Molecules act as visual anchors which will help faster recall during high-pressure exams.
Yes, teachers use our Class 9 Science resources for lesson planning as they are in simple language and have lot of solved examples.
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Yes, our subject matter experts have updated the Chapter 03 Atoms and Molecules material to align with the rationalized NCERT textbooks and have removed deleted topics and added new competency-based questions.