DensityDensity

The objective of study Define liquid density Difine solid density

If some oil is mixed with some water, what happens! The oil will be at upper of water. Why !

Imagine you have some cotton with 1 kg of mass and a stone with the same mass !

Why the volume of cotton is bigger than that of the stone, although they have the same mass?

The Ratio between Mass and Volume of Vegetable oil

Mass ( g ) Volume ( cm 3 ) Mass / Volume ( g/cm 3 )

The Ratio between Mass and Volume of water

Mass ( g ) Volume ( cm 3 ) Mass / Volume ( g/cm 3 )

No

ObjectsMass ( g)

Volume ( cm3 )Density ( g/cm 3 )

What is your conclusion?

You have learned that density does not depend on the size and shape of matter, The same matters with different sizes and shapes has the same density, while different matters with the same sizes and shapes have different density . So we can conclude that density is one of characteristics of matter

Calculating Density of an Object

To calculate the density of an object , we use the equation given in the previous section :

ρ = m / V

Look at the following examples!

1. 48 grams of a block of wood measures 6 cm long, 5 cm

wide , and 4 cm high. What is the density of the wood ?

Solution :Identified : m = 48 grams

l = 6 cm, w = 5 cm , h = 4 cm

Asked : ρ = ………..

Answer : V = l x w x h

= 6 cm x 5 cm x 4 cm

= 120 cm3

ρ = m / V = 48 g / 120 cm3

= 0,4 g/cm3

Exercise

1. 25 grams of stone is placed into a graduated glass filled with 30 mL. of water and completely submerged. The water level rises to 40 mL. What is the density of the stone ?.