We have discussed in the previous classes on different changes that
Now, just think about the changes involved in the following processes
in our daily life.
• The process of digestion.
• Burning of the crackers.
• The process of Respiration.
• Powdered lime added to water.
• Ripening of the Mango.
• Exposing iron nails to moisture in air for longer period.
What changes do you notice? Are they physical changes or chemical
changes ? Are they temporary changes or permanent changes?
In all the above processes, the nature of original substance would be
changed. If new substances are formed with properties completely unlike
to those of the original substances, we say that a chemical change has
taken place.
• How do we know that a chemical reaction has taken place?
