Question

a food item that is left out of the refrigerator turns brown and forms bubbles and gas. what are the signs that this is a chemical reaction? check all that apply. heat is produced. heat is absorbed. bubbles appear. a precipitate forms. the color changes.

Explanation:

The food turning brown is a color - change sign. The formation of bubbles and gas indicates a gas - evolution sign. There is no information about heat production/absorption or precipitate formation.

Answer:

C. Bubbles appear, E. The color changes