If two different liquids have the same volume will they have the same density? Why or why not?

Two liquids that
have the same volume don't necessarily have the same density. Density = mass/volume, so they
would only have the same density if they also have the same mass. 

Density is
an intensive property, which means that it doesn't depend on the amount of the substance
present. If two liquids have the same density, then any volume of the first substance will have
the same density as any volume of the second substance. Changing the volume of a substance
doesn't change the density.

As an example, mercury is a liquid metal whose
density is 13.5 times that of water. If you have 10 ml of mercury and 10 ml of water, the
mercury will have a mass of about 135g and the water will have a mass of 10g, so mass/volume of
the mercury is greater than that of water and mercury therefore has a higher density. This would
be true for any equal volume of the two substances.