What is the density of tap water and how can a property such as density be used to identify an unknown substance?

1 Answer
anor277
Oct 6, 2016

The density of water is #1*g*cm^-3#.

Explanation:

#"Density, "rho# #=# #"Mass"/"Volume"#. We assume a standard temperature of #298*K#.

#rho_"water"# is conveniently 1:1 with respect to volume and mass given appropriate units of mass and volume.

As liquids go, water is exceptionally dense, a property attributable to hydrogen bonding, and the strong intermolecular forces that exist between water molecules. Most organic solvents will float on water, and thus necessarily have #rho<1*g*cm^-3#.

The density of mercury metal is #13.55*g*cm^-3#. Will mercury float on water? The density of a pound coin is approx. #8*g*cm^-3#. Will a pound coin float on mercury metal?

If you have a table of densities, sometimes you can identify the substance if you measure its density. Usually, there are other more convenient means of identification.

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