Write any observations in an activity which may suggest that a chemical reaction has taken place. Give an example in support of your answer.

Explanation

The observations that suggest that a chemical reaction has occurred are :
Change in state, change in colour in temperature, evolution of gases, formation of precipitate.
e.g. : When a solution of potassium bromide is added to a solution of barium iodide it gives a yellow precipitate of potassium iodide and a barium bromide solution.