What do these two changes have in common?
using polish to remove tarnish from a silver spoon
a penny tarnishing

 - Both are chemical changes.
 - Both are caused by heating.
 - Both are caused by cooling.
 - Both are only physical changes.
Step 1: Think about each change.
A tarnished silver spoon is one that has become less shiny over time. Polishing the spoon makes it look shiny again.
The polish changes the tarnish into a different type of matter that can be easily wiped away. So, using polish to remove tarnish from silver is a chemical change.
Metal turning less shiny over time is called tarnishing. A penny tarnishing is a chemical change. When air touches the penny, the surface of the penny changes into a different type of matter. This matter makes the penny dull.
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.