What do these two changes have in common?
mixing lettuce and salad dressing
melting glass

 - Both are only physical changes.
 - Both are caused by cooling.
 - Both are chemical changes.
 - Both are caused by heating.
Step 1: Think about each change.
Mixing lettuce and salad dressing is a physical change. Together, the salad and dressing make a mixture. But making this mixture does not form a different type of matter.
Melting glass is a change of state. So, it is a physical change. The glass changes from solid to liquid. But a different type of matter is not formed.
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.
Glass melting is caused by heating. But mixing lettuce and salad dressing is not.
Both are caused by cooling.
Neither change is caused by cooling.