Study Guide
Density and Buoyancy
I.
Density
A.
Density is the amount of matter in a given
space. The formula for density
is: Density = mass/volume.
B.
Students should know how to solve density
problems.
C.
Students should know the definitions and units
for mass and volume.
D.
Know that density is a property of matter - no
matter how much you have of a pure substance, the density remains the same.
E.
Know that the density of water is 1 g/mL (1 g/cm3). And that objects with a density less
than 1.0 g/mL will float and objects with a density greater than 1.0 g/mL will
sink.
II.
Buoyancy
A.
Buoyancy is an upward force exerted by a fluid
(a fluid is substance that flows – a liquid or a gas). It is always an UPWARD force.
B.
Archimedes’ Principle states that for a floating
object, the weight of the object equals the weight of the water displaced.
C.
Be able to explain, using buoyancy, why some
objects float (like a heavy aircraft carrier) and some objects sink.
D.
If buoyant force is less than the weight of the
object, the object will sink. If
buoyant force is the same as the weight of the object, the object will
float. (Buoyant force can’t be
greater than the weight of the object because then the object would fly out of
the water!)
E.
Buoyant force is a force and is measured in
Newtons like weight.
(kg
x meters /seconds2 = Newton)
