Question

when do you tell that a chemical changes had occur

Answer 1

You will said that a chemical reaction is happen when
1] a new compound form which have no characteristics of element taking part in the reaction
2] if their is production of heat
3] if their is any change in colour
Andany more

Answer 2

Like in which effects ?

I know electric effect

Whenever the chemical change occurs in the circuit, then near electrodes the bubbles will form



OR


When ever a chemical reaction occurs we can see by changing of its size or shape or colour etc....



I think it is not applicable