Lesson ObjectivesBy the end of this activity, students will be able to:
understand how icebergs are suspended in water.
understand why ice floats.
describe the melting process of an iceberg.
differentiate between the floating behavior of ice and cork.
Related National StandardsNational Science Education Standards (National Research Council)
Science Standard B: Physical Science
Properties and changes of properties in matter
A substance has characteristic properties, such as density, a boiling point, and solubility, all of which are independent of the sample.
Materials Needed for Each Group
2 8-ounce paper cups
1 glass measuring cup
4 glass beakers (400 ml size)
mud or fine clay
graphite or charcoal dust
access to a freezer
Estimated Time to Complete Lesson
The paper cups should be filled as described in Procedure Step #1 the day
before the activity is done in class and placed into a freezer overnight. The
activity itself should take one class period.
Teaching StrategyBackground information
One milliliter (cubic centimeter) of liquid water weighs 1 gram, (i.e. the
density of water is 1.00 g/ml). Ice floats in water because its density (0.92
g/ml) is slightly less than that of water. Students will discover this when
they compare the mass and volume of liquid water with the mass and volume of the same
cup of water after it is frozen. The ice cup will weigh the same as when it was in liquid form
but the volume of ice in the cup will be larger than what it was in liquid form.
This is because when ice crystallizes into its
hexagonal structure the water molecules are farther apart than when they are in
the liquid state.
The density of the ice is so close to that of water that when ice floats more
than 90 percent of its volume is under the water. In contrast, a piece of
wood—whose density is 0.5 g/ml—will float with half its volume under water
since its density is half that of water. A piece of cork with a density of 0.2
g/ml will float with only 20 percent of its volume under water. While this
activity demonstrates how much of an iceberg actually exists under water, the
coffee cup-sized iceberg model differs from actual Antarctic icebergs in
several major aspects: its composition (mud and water), its shape
(cylindrical), its formation (the ice was not created under great pressure),
and its temperature (O°C, not below negative 50°C as are actual
Antarctica's ice sheets and ice shelf continuously discharge icebergs into the
Antarctic sea. These icebergs often have unusual shapes due to the weathering
effects. Some of these icebergs are almost as large as the state of
Connecticut. Almost 90 percent of the iceberg is under water, which makes
shipping and underwater exploration very hazardous (thus the expression "that's
only the tip of the iceberg").
The day before students do the floating iceberg activity have them make a
mixture of water and mud or water and fine clay. Then have each group label the two
paper cups and the glass measuring cup. Fill the cups with the following
cup 1 (paper cup): filled to the top with the water / fine clay or mud mixture
cup 2 (paper cup): filled half full with the water / fine clay or mud mixture
cup 3 (glass measuring cup): filled with pure water to the 275 milliliter mark
Once cup #3 has been filled, have students weigh it and record its mass and water volume.
Put the three cups into the freezer overnight.
The next day, have students weigh cup #3 again, record its mass, and record the volume of ice in it.
What happened to the volume of the liquid water as it froze? What happened to the mass?
(The density of a substance is defined as the
mass of substance per unit volume.) Once students have compared the mass and volume of the liquid vs.
frozen water, have them now consider a different scenario: If you take the same volume
of both water and ice, say exactly 1 cup of each, which of the two has more "stuff," i.e., water
molecules, in it?
Have students remove the ice from the cups so that cups 1, 2, and 3 now are just the
frozen "icebergs." Put the "icebergs" into three separate beakers that are half filled
with liquid water. Have students observe the three icebergs. Do they float in a
similar manner? Are there differences? What are they? Where is most of the ice
located, above or below the surface of the water? Have students estimate how
much volume of ice is above the water. Is it approximately the same for all the
Have students discuss how their model iceberg is different from the icebergs
found in Antarctica.
Sprinkle soot, graphite powder, or charcoal dust on iceberg #1. Put all 3
icebergs outside in the sun (or under a heat lamp). Observe the melting
behavior of the three. Which melts the fastest? Does melting occur in the water
or just in the air? Have students discuss the possible consequences of
industrial pollution settling out on the polar ice caps.
Have students put the cork stopper on top of the water in the fourth beaker. How does
its flotation differ from that of the "water" icebergs? Have students estimate
how much volume of the cork stopper is above the water. Have students propose
some possible reasons as to why when floating most of the cork is above the
water while most of the iceberg is below the water.
This site, devoted to Antarctica and the role it plays in Earth systems,
includes a section on ice and glaciers.
Students may be assessed through:
their participation in the activity.
the level of detail they provide in their observations. Very detailed
work would include information about what fraction of the volume was above and
below the level of the liquid, and about melting behavior in air versus in
water. The information would be presented in a clear, organized, and concise
being asked to draw and label a picture that diagrams the floating
iceberg and another diagram that depicts the floating cork. Students should
include a paragraph to describe how the flotation behavior is the same and how
it is different. Students may be asked to propose an explanation.
Experiment with different solutions. Students can put their iceberg
into different liquids such as rubbing alcohol or nail polish remover. What
happens? How can they explain this?
Determine the quantitative value for the density of liquid water and the
density of ice. To do this the student must make two additional
measurements beyond those described in procedure step #2. The student must
weigh the empty coffee cup to determine its mass. To determine the volume of
the cup fill it full of water and then pour the water into a graduated
Now the density of the water can be calculated:
(Mass of cup +water) - mass of cup = mass of water = density of water
volume of cup volume of water
In order to calculate the density of ice:
(Mass of cup +ice) - mass of cup = mass of ice = density of ice
volume of cup volume of ice
Determine the density of the cork by weighing it to get the mass and
determining its volume. One way to determine the volume would be to
calculate it according to its geometric shape and using the appropriate
formula. At this point the student may see a relationship between the density
and volume submerged when floating.
Investigate the types of icebergs and glaciers and how they are
formed. Students can use a map to locate some of the major glaciers in the
world. They can start their investigation of ices with Kingdom of Ice on
this Web site. (Requires Macromedia Flash Player)