What do these two changes have in common?
saliva breaking down a piece of bread
a banana getting ripe on the counter

 - 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.
Saliva breaking down a piece of bread is a chemical change. Bread is made up mostly of a chemical called starch. Saliva breaks the bonds between atoms in the starch molecules.
The atoms then link together to form smaller, simpler molecules of sugar. The sugar is a different type of matter than the starch.
A banana getting ripe on the counter is a chemical change. As a banana ripens, the type of matter in it changes. The peel changes color and the inside becomes softer and sweeter.
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.