Thursday, January 7, 2010

What is DENSITY ?

DENSITY is a physical property of matter, as each element and compound has a unique density associated with it. Density defined in a qualitative manner as the measure of the relative "heaviness" of objects with a constant volume.

For example: A rock is obviously more dense than a crumpled piece of paper of the same size.
A Styrofoam cup is less dense than a ceramic cup.

Density may also refer to how closely "packed" or "crowded" the material appears to be - again refer to the Styrofoam vs. ceramic cup.

The formal definition of density is mass per unit volume. Usually the density is expressed in grams per mL or cc. Mathematically a "per" statement is translated as a division. cc is a cubic centimeter and is equal to a mL Therefore,




Where:
m = mass (kg)
V = Volume (m3)
ρ = Density (kg/cm3)


Example: Calculate the density in g/mL of aluminum if a 50 mL block weighs 135 g.

Solution:
Apply the definition:


Density = 135 : 2,70 = 50 g/mL