Which is a sign that a chemical change is occurring a: boiling
b:bubbling
c:freezing
d:melting

B. Bubbling

Explanation:

The formation of bubbles are gas fumes, which are new products. The rest are only physical changes.

B.) Bubbling

Explanation:

The usual signs of a chemical change are color changes, the formation of a precipitate, the formation of a gas, an odor change, and temperature changes. Bubbles are an example of a formation of gas.

3

explanation:

the potential energy of the reactants is 200j.

from the energy diagram, the energy of the product formed is 350j; this means that, this reaction is an endothermic reaction, because it absorbs energy from its environment.