Which of the following is a definite indicator that a chemical change has occurred? a. a solid melts to form a liquid. b. a powder dissolves when mixed with a liquid. c. a gas forms when two liquids are mixed. d. a piece of copper is minted into a penny.

C.  A gas forms when two liquids are mixed.

Explanation:

In a physical change, no change in the composition of the material occurs. There might be change in the state of the matter. Examples of physical changes: Melting, cutting, freezing. option A, B and D are all physical changes.

In a chemical change, the composition of the matter changes. In option C, when two liquids mix, a gas forms which has different composition than the individual liquids.

where's the following? you gotta add it to know what the choices are

explanation:

a

explanation:

no diagram was provided, but i'm guessing it's the one i've attached to my answer.

here, a mechanical force turns the rod.   this generates an electric current in the coil, which powers the bulb.