Question

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

Answer 1

Explanation:

Density,

ρ

=

Mass

Volume

. We assume a standard temperature of

298

⋅

K

.

ρ

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

ρ

<

1

⋅

g

⋅

c

m

−

3

.

The density of mercury metal is

13.55

⋅

g

⋅

c

m

−

3

. Will mercury float on water? The density of a pound coin is approx.

8

⋅

g

⋅

c

m

−

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.