Density
The density at all points of a homogeneous object equals its total mass divided by its total volume. The mass is normally measured with a scale or balance; the volume may be measured directly (from the geometry of the object) or by the displacement of a fluid. To determine the density of a liquid or a gas, a hydrometer, a dasymeter or a Coriolis flow meter may be used, respectively. Similarly, hydrostatic weighing uses the displacement of water due to a submerged object to determine the density of the object.
Viscosity
where formula_58 is the Boltzmann constant, formula_59 the molecular mass, and formula_60 a numerical constant on the order of formula_61. The quantity formula_62, the mean free path, measures the average distance a molecule travels between collisions. Even without "a priori" knowledge of formula_60, this expression has interesting implications. In particular, since formula_62 is typically inversely proportional to density and increases with temperature, formula_10 itself should increase with temperature and be "independent" of density at fixed temperature. In fact, both of these predictions persist in more sophisticated treatments, and accurately describe experimental observations. Note that this behavior runs counter to common intuition regarding liquids, for which viscosity typically "decreases" with temperature.