Question

write down the observation which indicate the occurrence of chemical reaction

Answer 1

change in colour
change in temperature
evolution of gas
change in state
formation of precipitate

Answer 2

The following observations will takes place during the chemical reaction.

•    Change in physical state, temperature, colour of products, and also evolution of some gases.
•    A chemical reaction is a reaction in which a product that has chemical properties that differ from the original reactants is produced.
•    The chemical reactions occur in different ways combination, separation, or rearrangement of atoms.
•    Although the reaction causes changes at the atomic level, physical changes in the system can sometimes be observed indicating a chemical change is underway.