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
The water in the towel did not freeze, fall as droplets from the air, or melt — it warmed up and slowly turned into water vapor that drifted away. That change from a liquid to a gas at normal temperatures is evaporation.
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 stand on their own without needing a bowl or cup to hold them in shape, because their particles are locked together. Liquids do have a definite volume, gases have no definite shape, and solids do not flow, so the only true statement is that solids keep their shape without 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
On a cold morning, water vapor already in the air touches the icy glass and loses so much heat that it skips straight to a solid. Frost is that thin layer of ice formed when water vapor freezes onto the cold surface.
4. Which change of state requires removing heat from a substance?
A) Melting
B) Evaporation
C) Boiling
D) Freezing
Melting, evaporation, and boiling all need heat added to give particles more energy. Freezing is the opposite — heat has to be taken away so the particles slow down enough to lock into a solid.
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 shows up as ice when cold, as the liquid we drink at room temperature, and as vapor or steam when hot. The third form, when water spreads out into the air, is gas.
2. Removing heat from liquid water causes it to freeze into ice.
Pulling heat out of liquid water slows its particles until they lock into a fixed pattern. That cooling change from liquid to solid is what we call freezing.
3. The particles in a gas are spread far apart and move quickly.
Gas particles have lots of energy and almost nothing pulling them together, so they zoom in every direction. Because they hardly hold on to each other, they end up spread far apart.
4. Boiling water on a stove produces steam, which is water in the gas state.
When water on a stove gets hot enough, its particles fly off as a hot, fast-moving gas. The cloudy gas you see escaping from the pot is steam.
5. Matter can change state but the total amount of matter stays the same.
When something freezes, melts, or evaporates, its particles only rearrange — none of them disappear. So even as the state changes, the total amount of matter stays the same.