What do these two changes have in common?
a copper statue turning green
rust forming on a bicycle frame
Both are caused by heating. Both are only physical changes. Both are chemical changes. Both are caused by cooling.
Step 1: Think about each change.
A copper statue turning green is a chemical change. The copper reacts with oxygen in the air. This reaction forms a different type of matter called copper oxide. The copper oxide is green.
Rust forming on a bicycle frame is a chemical change. Oxygen in the air reacts with iron in the bicycle frame. The outside of the frame turns into a different type of matter called rust. Rust is reddish-brown and falls apart easily.
Step 2: Look at each answer choice.
Both are only physical changes.
Both changes are chemical changes. They are not physical changes.
Both are chemical changes.
Both changes are chemical changes. The type of matter before and after each change is different.
Both are caused by heating.
Neither change is caused by heating.
Both are caused by cooling.
Neither change is caused by cooling.