Which is a definite sign of a chemical reaction? Chemical properties change.

Physical properties change.

A gas forms.

A solid forms

Chemical properties change.

Step by step explanation

new substances formed, as evidenced by the color changes and bubbles. Some signs of a chemical change are a change in color and the formation of bubbles. The five conditions of chemical change: color change, formation of a precipitate, formation of a gas, odor change, temperature change.