Differentiate between physical and chemical changes.
Hint: Everyday, we come across so many different changes in our surroundings. These changes may have one or more substances involved. Essentially the difference between a physical reaction and a chemical reaction arises due to a difference in composition.
Complete step by step answer:
When a substance undergoes a physical change, its composition remains the same but there is rearrangement of molecules.
When a substance undergoes a chemical change, there is an entire change in its molecular composition, which results in the formation of new substances.
A Physical change is accompanied by change in physical properties of the substance, i.e. shape, size, color, state, etc.
Chemical change is accompanied by change in both physical and chemical properties of the substance, including its composition.
Physical changes are reversible in nature, i.e., original substance can be recovered.
Chemical changes are irreversible in nature, i.e., original substance cannot be recovered.
Physical changes do not have formation of new substances.
Chemical change leads to formation of new substances.
Examples- Freezing of water, melting of wax, boiling of water, cutting of paper into pieces, etc.
Examples- Rusting of iron, burning of coal, burning of magnesium ribbon, etc.
Note: Chemical changes require specific techniques to reverse back or prevent them from happening. For example, rusting of iron can be prevented by applying a layer of zinc or chromium on iron substance.