Chapter 2: Measurement and Problem Solving
 Calculate the density of a substance.
 Use density as a conversion factor.
 The density of a substance is the
ratio of its mass to its volume.
 Measuring mass: use a balance
 Measuring volume:
 Formula (l x w x h) (πr2h)
 Water displacement (Vf-Vi)
 Units of density:
 Solid substance = g/cm3
 Liquid substance = g/mL
 A sample of liquid has a volume of
22.5 mL and a mass of 27.2 g.
 D = m/V
m=
V=

For a liquid substance with a density of 1.32
g/cm3, what volume should be measured to
deliver a mass of 68.4 g?

A steel cylinder has a volume of 246 cm3 and
a density of 7.93 g/cm3. What is its mass in
kilograms?
 Density is an intensive property
 It does not change, no matter the size of a
sample
▪ 1 kg of gold has the same density as 1 g, or 1
lb, or 1000 kg, etc.
 Every substance has a unique density
 you can identify an unknown substance by
calculating its density and comparing it to
known values
 Density changes with temperature
 For most substances, an increase in
temperature results in a decrease in
density
▪ As temperature increases, molecules move
further apart. This increases the volume of the
substance while the mass remains the same –
thereby decreasing the density.
▪ So solids are more dense than liquids, which
are more dense than gases
 The density of liquid water is 1.00 g/mL
 Anything more dense than water will sink
 Anything less dense than water will float
 Water is one of a unique group of
substances that is actually less dense as
a solid than a liquid
 Ice floats in water!

A jeweler offers to sell a ring to a woman and tells
her that it is made of platinum. Noting that the ring
feels a little light, the woman decides to perform a
test to determine the ring’s density. She places the
ring on a balance and finds that it has a mass of
5.84 g. She also finds that the ring displaces 0.556
cm3 of water. Is the ring made of platinum? The
density of platinum is 21.4 g/cm3.
 Mass = 5.84 g
Volume = 0.556 cm3

The woman takes the ring back to the jewelry
shop, where she is met with endless apologies. The
jeweler had accidentally made the ring out of silver
rather than platinum. The jeweler gives her a new
ring that she promises is platinum. This time when
the customer checks the density, she finds the
mass of the ring to be 9.67 g and its volume to be
0.452 cm3. Is this ring genuine?
 Mass = 9.67 g
Volume = 0.452 cm3