Chemistry
Grade-8
Easy

Question

Which of the following statement is incorrect? 

  1. In a chemical reaction the matter is not created or not destroyed but only converts into one form to another.
  2. In the (N2O2) molecule, the ratio of the number of nitrogen and oxygen atoms is 2 : 2 but the mass ratio is 28 : 32.
  3. If reaction starts with 40 g of reactants, it should produce 40 grams of products.
  4. During the physical changes, the law of conservation of mass is not followed.

hintHint:

During the physical changes, the law of conservation of mass is not followed.

The correct answer is: During the physical changes, the law of conservation of mass is not followed.


    • Matter can change shape through physical and chemical changes, but each of these changes preserves matter.
    • The same amount of matter exists before and after the change, nothing is created or desA physical change can change the physical properties of matter, but not it's chemical composition.
    • For example, water is made up of two hydrogen atoms and one oxygen atom. Water is the only known substance on earth that occurs naturally in three states: solid, liquid, and gas.
    • Switching between these states requires a physical change in the water. When water freezes, it becomes harder and less dense, but chemically it is the same. There is the same number of water molecules before and after the change, and the chemical properties of water remain constant.

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