Definition of Density

"Mass per unit volume of a substance" is known as density.

Definition of Density

More About Density:

  • In S.I. system of units mass is measured in Kilograms, and the volume is measured in cubic meters (m3)
  • The units for density are Kg/ m3
  • Mass is measured with common balance and the volume is calculated by using different formulae for different types of objects
  • Example: Volume of a rectangular block = length x breadth x height ( l x b x h).
  • Find the volume of the following rectangular block
    Definition of Density
    Length = 4 m : Breadth = 3 m : Height = 1 m ;
    Volume of the rectangular block = 4 x 3 x 1 = 12 m3
    Volume of Irregular solid (if the shape is not in a regular form) the volume is calculated by using measuring cylinder.

Example: Find the mass of the following object

Definition of Density

  • Take a measuring cylinder.
  • Fill it partly with water and note the level of water level.
  • Lower the solid into a partly filled measuring cylinder.
  • Again note the water level. The rise in level on the volume scale gives the volume of solid. (Final water level � Initial water level).

  • Definition of Density

Worked Example:

An object of mass 100 g is immersed in water as shown in the diagram
What is the density of the material from which the object is made?

Definition of Density

    A. 0.4g/cm3
    B. 0.9g/cm3
    C. 1.1g/cm3
    D. 2.5g/cm3
Correct answer is "D".


    Step 1: Mass of the substance = 100 gm
    Step 2: Volume of the substance = 90 � 50 = 40 cm3
    Step 3: Density of the substance Density = mass / volume =100/40 = 2.5g / cm

Related Terms: Mass | Volume
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