States of Matter — Answer Key
Part A: Fix the Sentence
Each sentence has an error. Rewrite it correctly on the line.
1. Fix the sentence:
Melting is when a liquid changes into a solid.
Corrected: Melting is when a solid changes into a liquid.
Melting turns a solid into a liquid, not the other way around. Think of an ice cube melting into water — the solid changes into a liquid when heat is added.
2. Fix the sentence:
Air inside a balloon is a liquid.
Corrected: Air inside a balloon is a gas.
Air is a gas, not a liquid. You cannot see air and it spreads out to fill the whole balloon, which is how gases behave.
3. Fix the sentence:
A solid flows to fill its container like a liquid.
Corrected: A liquid flows to fill its container, but a solid does not.
Solids keep their own shape and do not flow. Only liquids flow and take the shape of whatever container they are poured into.
Part B: Fill in the Blank
Write the missing word or number on each line.
1. Tiny particles called molecules make up all matter.
All matter — solids, liquids, and gases — is made of tiny particles called molecules. These molecules are so small you cannot see them without a special microscope.
2. When water freezes, it changes from a liquid to a solid.
Freezing turns liquid water into ice, which is a solid. The cold temperature causes the water particles to slow down and lock into a fixed shape.
3. Helium inside a party balloon is a gas.
Helium is a gas that is lighter than the air around it, which is why helium balloons float upward. Like all gases, helium spreads out to fill the space inside the balloon.
4. A coin keeps its shape because it is a solid.
A coin is a solid, and solids keep their shape because their particles are packed tightly together. A coin stays round whether it is on a table or in your pocket.
Part C: True or False?
Read each statement. Circle True or False.
1. Heating ice causes it to melt into water.
True False
When ice absorbs heat, its particles speed up and break apart from their fixed positions, turning the solid ice into liquid water.
2. Gases always sink to the bottom of a container.
True False
Gases do not sink to the bottom — they spread out in every direction to fill the entire container. Gas particles move quickly and bounce around freely.
3. Milk is a liquid because it takes the shape of its glass.
True False
Milk is a liquid because it flows and takes the shape of whatever container you pour it into. If you pour milk from a carton into a glass, it changes shape to match the glass.