How can you conclude that the change in a substance is a chemical change ?

Explanation

1) The original substances lose their properties. Hence there may be products with different physical physical states and colours.
2) Chemical changes may be exothermic or endothermic that means they may involve heat energy liberation or heat energy absorption.
3) They may form an insoluble substance known as precipitate.
4) There may be gas liberation in a chemical change.