Density
Density is a physical property of matter that tells how close
together the molecules are in a substance. The more tightly
packed the molecules are, the more dense the substance is; the
less tightly packed, the less dense.
More dense
Less dense
A bowling ball and a beach ball may
have an identical size and shape. The
volume of each would be the same since
they would take up an equal amount of
space, but the bowling ball is much
heavier. Since the mass of the bowling
ball is greater, the density of the
bowling ball is also greater than the
density of the beach ball.
Density Formula
Volume
You can find the volume of an object
(such as a block ) by multiplying the
length X width X height. The mass
can then be found using a scale.
Density can be calculated using the
density formula.
Mass in grams
Volume
You can find the volume of an
irregularly shaped object (such as
a rock ) by using the water
displacement method shown in the
diagram. Mass can be found using
a scale and the density formula
can then be used to calculate the
density of the rock.
Volume of water after adding rock ––
Starting volume of water = Volume
of rock
Density is related to how heavy an
object feels. The mass of the hay
and the bricks below is equal as
shown by the balance, but the bricks
seem heavier. That is because the
density of bricks is much greater than
the density of hay.
Less dense
More dense
Water has a density of 1.0 g/mL.
Objects more dense than 1.0 g/mL will
sink in water. Objects less dense than
1.0 g/mL will float in water.
Water expands when it freezes and so
it takes up more space making it less
dense. This allows ice to float on top
of water.
The most important thing to remember is that density is a physical
property that can be calculated using the density formula.