What do these two changes have in common?
water vapor condensing on a bathroom mirror
your breath becoming visible on a cold day
A: Both are caused by heating.
B: Both are only physical changes.
C: Both are chemical changes.
Step 1: Think about each change.
Water vapor condensing on a bathroom mirror is a change of state. So, it is a physical change. The water changes state from gas in the air to liquid water on the mirror. But the water vapor and the liquid water are both made of water.
Your breath becoming visible on a cold day is a change of state. So, it is a physical change. Water vapor in your breath touches the cold air outside and becomes liquid. The water vapor changes state, but it is 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.
Both changes are caused by cooling.