Density can be defined by the mass of the substance over the volume which this
substance occupies. This is described by the well known equation D=m/ V, where D is
the density of the substance, m is the mass of the substance and V is the volume occupied
by the substance. The typical units for density are g/mL.
Density is an intensive property
of matter. This means that it does not depend on the mass of the substance present but
rather on the nature of the substance. Each pure substance has a defined, unchanging
density. As a result, density is very useful in determining the identity of an unknown
The purpose of this experiment was to determine the identity of an unknown
liquid based on its density using a procedure that we designed in order to maximize the
precision and accuracy of our measurements of the liquid’s density.
Part I: Distilled Water
The procedure was first tested on samples of distilled water, which is known to
have a density of about 0.997 g/ mL.
Distilled water was obtained in a 50mL beaker
A 30 mL beaker was cleaned, dried and massed on an analytical balance. The
analytical balance was chosen because provided a greater degree of precision
because it provided the mass to three decimal places. This mass was recorded.
10.00mL±0.04mL were measured in a clean calibrated pipet and placed in the
30mL beaker. The pipet was used because it provided a greater degree of
precision than the graduated cylinder, which provides an uncertain measurement
in the tenths place. (Before actually using the pipet for the procedure, the amount
delivered by the pipet was initially tested by measuring the amount of distilled