When substances are mixed and heated, a change can occur. The image below shows what happens when sodium is added to chlorine gas and burned. What demonstrates that this was a chemical change and not a physical change?
A. A new substance was formed when the sodium was burned.
B. Mass was conserved after the chlorine and sodium were mixed and heated.
C. Two substances with different properties were mixed together.
D. Both the solid sodium and the sodium chloride formed are solids.