ATOMS AND MOLECULES | SPEED NOTES | CBSE | SCIENCE | CLASS 9

Chapter 3- Atoms andMolecules Summary of Atoms andMolecules Law of conservation of mass: According to this law,during any physical or chemical change, the total mass of the products remains equal to the totalmass of thereactants. Law of constant proportion: Another French chemist, Joseph Proust, stated this law as 'A chemical compound always contains sameelements combined together in the sameproportion by mass'. Law of multiple proportion: John Dalton (1803) stated this law as 'when two elements combine with each other to form two or more than two compounds, the mass of the element which combine withthe fixed massof the other bears a simple whole number ratio'. Some important formulae: