The right answer is Change in color, production of gas, formation of precipitate.
Chemical changes alter the nature and characteristic properties of matter. New substances are formed as a result of the reaction.
It is said that a pure substance has undergone a chemical change if it has been transformed into one or more new pure substances which do not have the same properties as the starting substance.
The characteristic properties of the substances disappear and the products formed have new properties.
There are several (even more than three) that can recognize the presence of a chemical change.
* The formation of a gas (effervescence)
* Production or absorption of heat
* The production of bright light
* A significant color change
* A change of smell
* The formation of a precipitate
