Q21 of 28 Page 14

Define a chemical reaction. Which observations help you to determine whether a chemical reaction has taken place?

A chemical reaction is a process when two or more substances undergo a chemical change to form a new product.

The observations which help us to determine whether a chemical reaction has taken place:


i. New substances are formed by breaking and making of new


bonds.


ii. Some gases may evolve during the reaction.


iii. Change in the smell.


iv. Change in colour.


v. Change in state (liquid, solid or gaseous)


vi. Change in temperature.


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