States of Matter — Answer Key
Part A: Multiple Choice
Circle the best answer for each question.
1. Which state of matter has a definite volume but takes the shape of its container?
A) Solid
B) Liquid
C) Gas
D) Plasma
A liquid takes the shape of its container because its particles can slide past each other, but it keeps a fixed volume.
2. What happens to water when it is heated to its boiling point?
A) It freezes into ice
B) It stays the same
C) It evaporates into water vapor
D) It becomes heavier
The sun's heat causes the liquid water to evaporate, changing it into water vapor (a gas) that rises into the air.
3. Which is an example of condensation?
A) Ice cubes melting in a glass
B) A puddle drying in the sun
C) Water droplets forming on a cold can
D) Snow falling from clouds
When warm water vapor in the air touches the cold surface of a can, it cools and turns into liquid water droplets — this is condensation.
4. Why does a gas fill its entire container?
A) Its particles are packed tightly
B) Its particles move fast and spread apart
C) Its particles do not move at all
D) Its particles are heavier than liquid
Gas particles have a lot of energy and move quickly in all directions, while solid particles are packed tightly and vibrate in place.
Part B: Fill in the Blank
Write the correct answer on each line.
1. The temperature at which ice melts into water is 0 degrees Celsius.
Water freezes at 0 degrees Celsius (32 degrees Fahrenheit), changing from a liquid to a solid.
2. Adding heat to a substance makes its particles move faster.
Adding heat gives particles more energy, causing them to move faster and spread farther apart.
3. When water vapor cools, it condenses back into liquid water.
Condensation occurs when water vapor (gas) cools down enough that the particles slow down and form liquid water.
4. A chocolate bar left in the sun will melt because heat changes its state.
Heating ice adds energy to the solid water, causing the particles to move apart and change into liquid water.
5. The process of a liquid changing into a solid is called freezing.
Freezing is the process where a liquid loses heat and its particles slow down enough to form a solid.