How do we come to Know that a chemical reaction has taken place ?

1.	How do we come to Know that a chemical reaction has taken place ?
Answer» The presence of any of the following changes helps us to determine that a chemical reaction has taken place.\tFormation of new substance(s)\tChange in state\tChange in colour\tChange in temperature\tFormation of a precipitate\tEvolution of a gas\tFor example, if on mixing two substances a gas is evolved, then we can say that a chemical reaction has taken place.

Discussion