Among the several physical properties that you may need to convert between process variables is the density , used to convert volumetric flowrate to mass flowrate. It is the ratio of mass of the substance (mixture) to its volume. For water, the density is 1000 kg/m³ (at 4^oC) and this is used as a reference density for liquid. As for gases, air with density of 1.225kg/m3 (at 15^oC) is used. However, process liquids streams may not enters the process at 4^oC or 15^oC. Temperature and pressure would then affect the density of fluid and the effect is more significant when the fluid is in gas state.

In your own words, express how would increasing the temperature & pressure will affect fluid density and why the effect is more noticable with gas fluid, compare to liquids and solids.