Introduction to Density
 Density is the measurement of the mass of an
object per unit volume of that object.
d=m/V
 Density is usually measured in g/mL or g/cm3 for
solids or liquids.
 Volume may be measured in the lab using a
graduated cylinder or calculated using: Volume =
length x width x height if a box or V = pr2h if a
cylinder.
 Remember 1 mL = 1 cm3
How to measure the density of a
solid in the laboratory.
• Obtain a clean graduated
cylinder.
• Fill the graduated cylinder with
enough water to cover the object.
Record the volume
• Carefully place the object into
the water filled graduated
cylinder.
• Record the new water level.
• The volume of the object is the
Vfinal – Vinitial.
Introduction to Density
Example: An object has a mass of 50.0 g and
occupies a volume of 52.0 mL. What is its
density?
d = m / V = 50.0 g / 52.0 mL = 0.98 g/mL
Example: A cylinderical piece of metal is 2.03
inches high and has a diameter 17.0 mm wide and
weighs 31.599 g. Identify the metal.
V=pr2h = p (1.70 cm/2)2 * (2.03 in [2.54 cm/1in]) =11.7 cm3
D = m/V = 31.599 g / 11.7 mL = 2.70 g/mL
The metal is aluminum!
Practice Problems #3 on density
Show all of your work on the back. Use scientific notation when necessary and
always given your answers with the appropriate significant figures.
15.9 mL 1. Calculate the volume, in microliters, of a
• ___________
cylinder that is 32.42 mm long with a diameter of 0.0789 cm.
•
1.58 g/mL 2. Calculate the density of a solution if 45.0 mL
___________
of the solution weighs 7.12 x 10-2 kg.
•
3
2.59
cm
___________ 3. The Hope diamond weighs 45.52 carats and
has a density of 3.51 g/cm3. What is the volume of this
diamond? (1 carat = 200 mg)
3; sink
2.0
g/cm
• ___________ 4. A plastic material weighing 2.2 lb is shaped
into a cylinder 13.5 cm in height and 6.8 cm in diameter. Will
this object sink or float in water?
•
3.29 g/mL 5. A student fills a 50.0 mL graduated cylinder
___________
with 25.0 mL of water, then places a spherical object weighing
54.367 g into the graduated cylinder. The new volume is 41.5
mL. Calculate the density of the object.
Group Study Problem #3 on Density
Record your final answer on this sheet and show all of your work on the back. Use scientific notation
when necessary and always given your answers with the appropriate significant figures.
• ___________ 1. Calculate the volume, in liters, of a box that is 189
mm long by 6.75 cm wide by 7.88 in high.
•
___________ 2. Calculate the density of a liquid if 13.476 mL of the
liquid has a mass of 1156 cg.`
•
___________ 3. What mass of mercury will occupy a volume of 10.0
cm3 if it has a density of 13.6 g/ml?
•
___________ 4. What is the density (in g/ml) of a substance that
weighs 2.672 lb. and occupies a volume of 7.98 qt.
•
___________ 5. The mass of an irregular shaped object was
measured to be 76.58 g. A student fills a 50.0 mL graduated cylinder
with 20.0 mL of water, then places the object into the graduated
cylinder. The new volume is 37.5 mL. Calculate the density of the
object.