Question

Define a chemical reaction. What changes is presented by a chemical reaction?

Answer 1

chemical reaction is the reaction taken place between two or more elements or compounds which cause in change in their chemical properties.

change in chemical reaction are:-
the substance we will get will have completely different properties such as smell , colour , their shape n size ( not necessary)
they cannot be reversed from any physical methods

Answer 2

A process in which new substances having composition and properties entirely different from the original substance are formed is called chemical reaction
changes:
1. Rusting of iron
2.Curding of milk
3. Burning of substances in air (like burning of paper)
4. Digestion of food
5. Respiration
6. Boiling of an egg
hope it is helpful for u :)