Question

single red crystal is heated as the temperature heats up it begins to break, and a green gas is made. as t crystal melts it changes from red to brown. based on this information you can determine that the crystal i

Explanation:

A compound is a substance formed when two or more elements are chemically bonded together. When the red crystal is heated, it decomposes (breaks down) into different substances (a green gas and a brown - colored substance upon melting). An element cannot be broken down into simpler substances by chemical means. A mixture can be separated by physical means, but here a chemical change (decomposition) is occurring. A solution is a homogeneous mixture, and the description does not fit that of a solution.

Answer:

C. A compound