Density = mass / volume
So in order calculate the density of the unknown liquid, we need to know
its mass and its volume.
If the mass of the beaker is 165 grams empty and 309 grams with
something in it, then the mass of the stuff in it must be
(309 - 165) = 144 grams.
The question tells us that its volume is 125 mL (same as 125 cm³),
so we have everything we need.
Density = mass/volume = 144/125 = 1.152 grams per cm³ .
The density of pure water is 1.000 gram per cm³ , so the unknown liquid
is definitely not pure water.
The density of this unknown liquid is 15.2% more than that of pure water.
Even if water had a huge amount of pollution and junk in it, its density
would probably not be that much greater than 1.000 . So the unknown
liquid is probably not polluted water either.
