States of Matter — Answer Key
Part A: Multiple Choice
Circle the best answer for each question.
1. A wet towel dries on a clothesline. Which process caused the water to disappear?
A) Freezing
B) Condensation
C) Evaporation
D) Melting
Evaporation is the process where liquid water gains enough heat energy for its particles to escape into the air as water vapor.
2. Which statement about solids, liquids, and gases is correct?
A) Solids flow easily like liquids
B) Liquids have no definite volume
C) Gases have a definite shape
D) Solids keep their shape without a container
Solids have a definite shape because their particles are tightly packed and hold their positions, unlike liquids and gases which need a container.
3. What causes frost to form on a window on a cold morning?
A) Water evaporates from the glass
B) Water vapor in the air freezes on the cold surface
C) The window melts and creates ice
D) Rain falls directly onto the glass
When warm, moist air touches the cold window, the water vapor freezes directly onto the glass surface, forming frost.
4. Which change of state requires removing heat from a substance?
A) Melting
B) Evaporation
C) Boiling
D) Freezing
Freezing is the process where liquid water loses enough heat for its particles to lock into a solid structure, forming ice.
Part B: Fill in the Blank
Write the correct answer on each line.
1. Water can exist as a solid, a liquid, or a gas depending on temperature.
Water vapor is the gas form of water — its particles are spread far apart and move very quickly.
2. Removing heat from liquid water causes it to freeze into ice.
Freezing happens when liquid water is cooled to 0 degrees Celsius, causing its particles to slow down and form solid ice.
3. The particles in a gas are spread far apart and move quickly.
Gas particles have a lot of energy and are spread far apart, which is why gases have no definite shape or volume.
4. Boiling water on a stove produces steam, which is water in the gas state.
Steam is visible water vapor that rises from boiling water as the liquid rapidly changes to gas.
5. Matter can change state but the total amount of matter stays the same.
Matter is anything that has mass and takes up space — solids, liquids, and gases are all forms of matter.