States of Matter — Answer Key
Part A: Multiple Choice
Circle the best answer for each question.
1. A chocolate bar is left in a hot car. What will it become?
A) A harder solid
B) A melted liquid
C) An invisible gas
D) A block of ice
Heat from the car warms the chocolate, so the solid melts into a soft liquid.
2. A pot of soup boils on the stove. Some of the liquid becomes what?
A) Solid chunks
B) Heavier liquid
C) Steam, a gas
D) Ice
Boiling turns liquid water in the soup into steam, which is a gas that rises.
3. Juice is put in the freezer for a long time. What will it become?
A) Warm gas
B) Hot liquid
C) Frozen solid
D) Invisible air
The freezer makes the juice very cold, so it freezes into a solid popsicle.
4. A puddle of water in the sun slowly gets smaller. Where does the water go?
A) Into the ground only
B) Into the air as gas
C) It disappears from matter
D) It turns to rock
Sun heat changes liquid water into a gas that goes up into the air.
Part B: Fill in the Blank
Write the correct answer on each line.
1. Heating a solid enough makes it melt into a liquid.
Melting is the change from solid to liquid caused by adding heat.
2. Cooling a liquid enough makes it freeze into a solid.
Freezing is the change from liquid to solid caused by taking heat away.
3. Boiling a liquid enough turns it into a gas.
Boiling gives enough heat to change liquid into its gas state.
4. If you cool steam down, it turns back into a liquid.
Cool air takes heat from the steam and changes it back into liquid water drops.
5. Adding or taking away heat can change the state of matter.
Heat is the key: more heat makes matter flow or spread; less heat makes it firm up.