Gases will fill any space that they are allowed into. In a liquid state, molecules touch one another and interact with one another. In a gas state, molecules will rarely bump into one another they are too far apart. Liquefaction of a gas occurs when the molecules start moving slower and slower and get closer and closer together. In a liquid molecules are touching one another and interacting with one another.
Boiling point is the temperature at which a liquid boils.
Odors are detected when some molecules escape the liquid phase and enter the gas phase. That is when a liquid evaporates, it forms into a gas. Our sense of smell only can detect gas molecules not liquid. The molecules essentially quit moving around. They slow down so much that the material becomes rigid.