Answer the following question: Answer the following question given this paragraph: A: Another example of matter changing color is a penny changing from reddish brown to greenish brown as it becomes tarnished. The color change indicates that a new chemical substance has been produced. Copper on the surface of the penny has combined with oxygen in the air to produce a different substance called copper oxide. Q: What substance is created when a copper turns from reddish brown to greenish brown? Choices: - rust - copper alloy - iron oxide - copper oxide A:
Answer:
copper oxide