What do these two changes have in common?
cellular respiration
compost rotting

 - Both are chemical changes.
 - Both are only physical changes.
 - Both are caused by heating.
 - Both are caused by cooling.
Step 1: Think about each change.
Cellular respiration is a chemical change. Cells use oxygen to break down sugar. Breaking the chemical bonds in sugar molecules releases energy that a cell can use.
The atoms from the broken molecules then combine to form different molecules such as carbon dioxide and water. These molecules are different types of matter than sugar and oxygen.
Compost forms from the remains of plants and animals, such as vegetable scraps and egg shells. Compost rotting is a chemical change. As the compost rots, it breaks down and turns into a different type of matter.
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.