What do these two changes have in common?
breaking a piece of glass
dew appearing on grass in the morning
A: Both are only physical changes.
B: Both are chemical changes.
C: Both are caused by heating.
D: Both are caused by cooling.
Step 1: Think about each change.
Breaking a piece of glass is a physical change. The glass gets broken into pieces. But each piece is still made of the same type of matter.
Dew appearing on grass in the morning is a change of state. So, it is a physical change. Water vapor in the air touches the cool grass and becomes liquid.
The water vapor changes state to become dew, but it is still made of water. 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.
Neither change is caused by heating.
Both are caused by cooling.
Dew appears when water vapor in the air condenses into a liquid on the grass. This is caused by cooling. But breaking a piece of glass is not.