A self-warming packet can be used to warm hands during cold weather. Powdered iron (Fe) reacts with oxygen (O₂) when the packet is exposed to air. With the addition of a salt catalyst, Fe₂O₃ (iron oxide) is quickly formed and heat is given off. 4Fe+3O₂ --> 2Fe₂O₃.
Which term best describes iron oxide?
A. compound
B. element
C. ion
D. mixture
