What do these two changes have in common?
bending a paper clip
mixing sand and water

 - Both are chemical changes.
 - Both are caused by cooling.
 - Both are caused by heating.
 - Both are only physical changes.
Step 1: Think about each change.
Bending a paper clip is a physical change. After you bend it, the paper clip has a different shape. But it is still made of the same type of matter.
Mixing sand and water is a physical change. Adding water makes the sand wet. But both the sand and water are still made of the same type of matter as before.
Step 2: Look at each answer choice.
Both are only physical changes.
Both changes are physical changes. No new matter is created.
Both are chemical changes.
Both changes are physical changes. They are not chemical changes.
Both are caused by heating.
Neither change is caused by heating.
Both are caused by cooling.
Neither change is caused by cooling.