What do these two changes have in common?
an engine using gasoline to power a car
melting glass
A: Both are caused by cooling.
B: Both are only physical changes.
C: Both are chemical changes.
D: Both are caused by heating.
Step 1: Think about each change.
An engine using gasoline to power a car is a chemical change. High temperatures in the engine break the chemical bonds in the molecules of gasoline and release energy. The atoms then link together to form new molecules, such as water, carbon dioxide, and other chemicals.
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.
Melting glass is a physical change. But an engine using gasoline to power a car is not.
Both are chemical changes.
An engine using gasoline to power a car is a chemical change. But melting glass is not.
Both are caused by heating.
Both changes are caused by heating.
Both are caused by cooling.
Neither change is caused by cooling.