density Flashcards
Density is
the mass per unit volume of a material:
it is measured in
kg/m3 or
g/m3
g/cm3
density symbol
p
Objects made from low density materials typically have
a low mass
volume symbol and unit
V m3
Density is related to mass and volume by the following equation:
The units of density depend on what units are used for mass and volume:
If the mass is measured in g and volume in cm3, then the density will be in g/cm3.
If the mass is measured in kg and volume in m3, then the density will be in kg/m3.
The main thing to remember is that density is
mass per unit volume.
density is greater when the object is a
and smaller when is a
the exception is …because
so ice… in water
solid
liquid
water as solid is less dense than when liquid
floats
Floating
an object will float in a liquid if the average density of that object is less than the density of the liquid it is placed in.
Measuring Density
To measure the density of an object, we must measure its mass and volume and then use the following equation:
The mass of an object can be measured quite simply by placing it on a
You ought to state that you will the balance before using it.
top pan balance or mass balance
‘zero’
measurements In the case of a liquid,
the liquid must be placed in a container, the mass of which should be measured both when it is empty and when it contains the liquid:
The mass of the liquid will be the difference between the two values.
The volume can be determined in a couple of ways depending if
it is a regular shape or not
regular shapes
Regular shapes (e.g. cubes, spheres, cylinders):
The width (and length) can be measured using a ruler or a pair of digital calipers.
To make the measurements accurate, several measurements should be taken between different faces or points on the circumference, and an average taken.
The volume can then be calculated using an appropriate equation:
Irregular shapes:The volume can be found using a Eureka can:
The volume can be found using a Eureka can:
Fill the Eureka can with water.
Place an empty measuring cylinder below its spout.
Now carefully lower the object into the Eureka can (use a piece of string, perhaps).
Measure the volume of displaced water in the measuring cylinder.
Alternatively, the object can be placed in a measuring cylinder containing a known volume of liquid, and the change in volume then measured.
Once the mass and volume of the shape is known, its density can be calculated.
