Find the density of an unknown liquid in a beaker. the empty beaker's mass is 165
grams. with the unknown liquid inside the beaker, the total mass is 309 grams. the
volume of the unknown liquid is 125ml. is the liquid pure water? explain your answer.

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.