Do solids liquids and gases have a definite volume?

Solids have a set volume.

Liquids have a set volume.

Gases do not have a set volume.

Why?

Solids are solids. They don't move. They're in a 'frozen state' as is.

Liquids 'mold' to the shape of their container and they stay there.

Gases are free to go anywhere. Always moving and 'flying.'