What do these two changes have in common?
acid rain weathering a marble statue
milk going sour

 - Both are caused by heating.
 - Both are chemical changes.
 - Both are only physical changes.
 - Both are caused by cooling.
Step 1: Think about each change.
Acid rain weathering a marble statue is a chemical change. The acid rain reacts with the outside of the statue and breaks it down into a different type of matter. This new matter is then washed away by the rain. Acid rain is a type of pollution. It forms when smoke from automobiles and factories mixes with water in clouds.
Acid rain is a type of pollution. It forms when automobiles and factories release smoke containing sulfur or nitrogen. Some of these chemicals react with water in the atmosphere. The reaction forms droplets of water that can fall back to the ground as acid rain.
Milk going sour is a chemical change. The type of matter in the milk slowly changes. The new matter that is formed gives the milk its sour taste.
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.