Density
•describes how closely
packed the particles are in
a solid, liquid or gas.
•amount of mass per unit
volume.
• All matter contains small particles called atoms.
• The difference between the different states of
matter is how the particles are arranged:
in a solid – particles are tightly packed in a regular
structure
in a liquid – particles are tightly packed but free to
move past each other
in a gas – particles are spread out and move
randomly
Density also depends on the material.
For example:
A piece of iron with the same dimensions
as a piece of aluminium will be heavier
because the atoms are more closely
packed.
Calculating density
•density (ρ) is measured in grams per cubic metre (g/m3)
•mass (m) is measured in grams (g)
•volume (v) is measured in cubic metres (m3)
Mass
-The amount of matter an object has.
-Unit of measurement =
-What tool do we use to find mass?
Volume
• If the object is a regular shape, the volume can be
found by using a ruler and then using the equation:
• Volume = length × width × height
• If the object has an irregular shape, the volume can
be measured using a displacement/eureka can.
• The displacement can is filled with water below a
narrow spout and allowed to drain until the water is
level with the spout.
Volume
The quantity of space an object occupies.
-Unit of measurement =
so which one do you use when?
-What tools can we use to find volume?
Finding Volume of an Irregular Shaped Object (8Am)
-Can’t use a ruler!!!
-Find volume by water displacement method.
-Volume of water with object – volume of water before
object
-Don’t forget to read the graduated cylinder from the
bottom of the meniscus!!!
What is the reading
on this graduated
cylinder?
How about this one?
Last one!
What is the density of a material of 0.45 cubic
metres (m3) if it has a mass of 0.2 kg?
= 0.44 kg/m3
There are different ways to investigate density.
In an experiment to determine density of liquids
and solids, it is important to:
• record the mass accurately
• measure and observe the mass and the volume
of the different objects
• use appropriate apparatus and methods to
measure volume and mass and use that to
investigate density
Note and make a point to remember :
• Density of water = 1.0 g/cm3 OR
1.0 g/ml
Errors when determining densities
When taking measurements:
1)This the top pan balances used by different people
may not be identically calibrated
2) resolution of the measuring cylinders may be
different, causing different values for the volume to be
recorded
Why is Density Important?
-Any ideas?
-Consider 1 kg of iron and 1
kg of cotton….
-Every element has its own
unique density. How
could that help?