Class9_Science_Atoms and Molecules

In any chemical reaction, the total mass of the substance before and after the reaction is the same although its matter undergoes a physical change.
law of definite proportions :
"In a chemical substance the elements are always present in definite proportions by mass".
Law of Multiple Proportions
When two elements combine to form different compounds, then the weight of one is constant and the other has a simple ratio.

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