The volume will not change significantly under pressure.

Liquids can be considered non-compressible. When a liquid is placed in a container, it assumes the shape of the container but the volume and mass remain the same under constant temperature and pressure. Liquids are fluids that have a definite volume of their own that is independent of the shape and volume of the container. This is explained later with Dalton's law of partial pressures. However, the moisture content of air is water vapor (steam) at a temperature of, say, 70 oF. For example, water boils at 212 oF (100 oC) at standard atmospheric pressure of 14.7 pounds per square inch absolute (psia), and becomes steam at 212 oF. Vapors are gases that can condense at everyday atmospheric pressures and temperatures whereas dry gases condense at very high pressures and very low temperatures. Two containers of different volumes can contain the same mass of gas. The volume of gas in an enclosed container is the volume of the container. They are affected by temperature and pressure. A gas has no shape and it assumes the volume of the container that it is confined in. Gases are fluids that do not have a definite volume. They cannot be torn, fractured or broken into smaller pieces. They cannot sustain shear (lateral) stress under equilibrium conditions. They have no consistent shape when it is not confined a container. Fluids have a definite mass and volume at a given temperature and pressure. The term 'Fluid' consists of gases and liquids. The study of HVAC requires understanding gases (particularly Air) and liquids (particularly Water). For example, the flow of air in ducts and the flow of water in pipes are based on the same theory and equations. Fluids have common performance characteristics. Liquids and gases can be grouped together as Fluids. This is theoretically true of all elements and compounds. They are solid (ice), liquid (water) and gas (steam). The compound H 2O (2 molecules of the element Hydrogen combined with 1 molecule of the element Oxygen) can exist in 3 states.

Solid to liquid