How are chemical changes different from physical change

Chemical changes and physical changes are different in several ways:

1. Nature: A chemical change involves the formation or breaking of chemical bonds, resulting in the creation of new substances with different properties. In contrast, a physical change does not involve any change in the chemical composition or bonding of a substance.

2. Reversibility: Physical changes are often reversible, meaning the substance can return to its original state after undergoing the change. On the other hand, chemical changes are typically irreversible, as they involve the formation of new substances which cannot easily be reversed.

3. Energy Changes: Chemical changes often involve the absorption or release of energy in the form of heat, light, sound, or electricity. Physical changes typically do not involve any energy changes.

4. Observability: Physical changes can often be observed directly, such as changes in shape, size, or state of matter, without the need for chemical tests. In contrast, chemical changes often require specific indicators or tests to observe the formation of new substances.

5. Stoichiometry: Chemical changes follow the principles of stoichiometry, which dictate the ratio of reactants and products involved in a chemical reaction. Physical changes do not involve any change in stoichiometry.

Overall, chemical changes involve a transformation at the molecular level resulting in the formation of new substances with different properties, while physical changes only involve alterations in the state or appearance of a substance without any changes in the chemical composition.