37. Which of the following processes is/are chemical changes?
1. Extracting iron from iron ore
2. Explosion of a firework
3. Stretching a rubber band
b. 1 and 2 only
A change in which one or more new substances are formed is called a chemical change. A chemicalchange is also called a chemical reaction. For eg - Explosion of a firework
A change in which a substance undergoes a change in its physical properties is called a physical change.
A physical change is generally reversible. In such a change no new substance is formed. For eg. Stretching rubber band represents a physical change.