DETERMINATION OF SPECIFIC GRAVITY OF
A LIQUID
Aim: To
determine the specific gravity of a liquid.
Apparatus: hydrometer,
500ml measuring cylinder/hydrometer jar, thermometer.
Sample: any liquid
Significant: To know the weight of the liquid
Theory/Definition:
Specific
gravity is a dimensionless unit defined as the ratio of density of the material
to the density of water. if the density of substance of interest and reference
substance (water )are known in same units (e.g. both in g/cm^3 or lb/ft^3) then
the specific gravity of the substance is equal to it density divided by that of
reference substance (water =1g/cm^3). The greater the density the tighter or
closer the molecule are packed inside the substance. Therefore the greater the
specific gravity/density of a liquid the higher a hydrometer will buoyed by it
Hydrometer:is an
instrument whose function is base on Archimedes principles.
The principle stated that a body
(hydrometer) immersed in a fluid are buoyed up by a force equal to the weight
of the displaced fluid. The hydrometer measures the weight of the liquid displaced
by the volume of the hydrometer.
Procedure / steps involved for the
determination of specific gravity of a liquid:
- Fill the hydrometer jar about ¾ with the liquid you
wish to test.
- Insert the hydrometer slowly, do not drop it in,
then give it a spin with your thumb and index finger, this will dislodge any
bubble that will form.
- Once the hydrometer comes to rest observe the plane
of the liquid surface. Your eyes must be horizontal to this plane. (The point
at which this line cuts the hydrometer scale is your readings).
- Insert your thermometer and take the temperature
reading
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