In the Classroom
www.JCE.DivCHED.org • Vol. 81 No. 4 April 2004 • Journal of Chemical Education 509
When teaching general chemistry, it is often a challenge
to keep the subject matter interesting for the students and
fresh for the instructor. Taking examples from science fiction
(1) or science in fiction (2) has been used as a way to
boost interest in selected topics. While motivating the students
is a worthy goal in itself, utilizing examples from another
discipline such as literature may serve to show how
seemingly remote topics such as chemistry and fiction are related
to each other. A liberal education is about seeing the
“big picture” and how each subject has an impact on other
subjects. In addition, it is necessary to strengthen students’
understanding of specific concepts by applying their knowledge
to new situations. Using examples from science fiction
certainly provides new situations to consider and also serves
to reinforce the idea that the laws of nature are universal.
Even if a situation is fictitious, concepts such as thermodynamics
can still be applied.
While teaching thermodynamics to introductory students,
I use an example taken from Kurt Vonnegut, Jr.’s, novel
Cat’s Cradle (3). In the story, an absentminded scientist1
discovers
a form of solid water, known as ice-nine, which is stable
at room temperature. When a seed crystal of ice-nine is accidentally
introduced into the ocean, the ocean immediately
solidifies into ice-nine, eventually leading to the end of life
on Earth. Any people who come into direct contact with icenine
are likewise instantly “frozen”. With only a brief introduction
to the story, students are able to apply what they
have learned about thermodynamics and make some rather
interesting conclusions about the process of forming ice-nine.
Using the information covered in a typical general chemistry
course, it can be shown that the process of crystallizing
all of the liquid water on Earth must be highly exothermic
and lead to a significant increase in the global temperature.
Although ice-nine is fictitious, it does have some interesting
ties to the real world (4). The author of the story, Kurt
Vonnegut, Jr., graduated from Cornell University with a major
in chemistry. Vonnegut took a job in the public relations
office at General Electric where his older brother, Bernard,
was working in the lab and had discovered how to use silver
iodide particles for seeding clouds to precipitate rain and
snow. The author Vonnegut credits the invention of ice-nine
to Irving Langmuir, who pioneered the study of thin films
and interfaces. While working in the public relations office
at General Electric, Vonnegut came across a story of how
Langmuir, who won the 1932 Nobel Prize for his work at
General Electric, was charged with the responsibility of entertaining
the author, H. G. Wells, who was visiting the company
in the early 1930s. Langmuir is said to have come up
with an idea about a form of solid water that was stable at
room temperature in the hopes that Wells might be inspired
to write a story about it. Apparently, Wells was not inspired
and neither he nor Langmuir ever published anything about
it. After Langmuir and Wells had died, Vonnegut decided to
use the idea in his book, Cat’s Cradle.
When covering thermodynamics in the general chemistry
curriculum, I introduce a discussion of ice-nine to tie together
the concepts of enthalpy, entropy, and spontaneity.
While the thought of water spontaneously (and instantly)
freezing at room temperature may seem so far beyond the
realm of possibilities to even consider, such phenomena are
seen with supersaturated solutions and super cooled liquids.
To add a stunning visual effect to the discussion, a demonstration
of a supersaturated sodium acetate solution (5) instantly
crystallizing onto a watch glass containing a seed
crystal, the so-called “pillar of salt”, is shown to the students.
We then consider the thermodynamics of the analogous but
fictitious ice-nine. The question of whether the formation
of ice-nine should be exothermic or endothermic may appear
to be too difficult for many students at first, but if the
question is presented stepwise, many students are able to
come up with reasonable answers. The problem is presented
in two parts (Parts A and B below). After working through
the qualitative aspects of ice-nine formation and determining
that the formation of ice-nine must be highly exothermic,
we then consider some more quantitative aspects. The
assignment is given in two parts since some of the questions
in Part B contain answers to some of the questions in Part
A. The questions below have been designed to lead the students
through the thinking process one step at a time.
The Assignment
The students are presented with the following brief introduction
to ice-nine and related questions in Part A prior
to the discussion:
In the Kurt Vonnegut, Jr., novel Cat’s Cradle, a hypothetical
substance known as ice-nine destroys the world. Ice-nine is
described as a crystalline compound, composed of H2O
molecules that are arranged in a different way than the molecules
in “regular” ice. This alternate arrangement of H2O
molecules gives ice-nine its unique properties. For example,
ice-nine is blue–white in appearance, and has a melting point
of 114.4 ЊF. When a seed crystal of ice-nine is introduced
into the ocean, it solidifies instantly. The event is described
as follows (3):
I closed my eyes.
There was a sound like that of a gentle closing of a portal as big
as the sky, the great door of heaven being closed softly.
It was a grand AH-WHOOM.
I opened my eyes-and all the sea was ice-nine.
The moist green earth was a blue white pearl.
The sky darkened. Borassi, the sun, became a sickly yellow ball,
tiny and cruel.
The sky was filled with worms. The worms were tornadoes.
Using Science Fiction To Teach Thermodynamics: W
Vonnegut, Ice-nine, and Global Warming
Charles A. Liberko
Department of Chemistry, Cornell College, Mount Vernon, IA 52314-1098; cliberko@cornellcollege.edu
In the Classroom
510 Journal of Chemical Education • Vol. 81 No. 4 April 2004 • www.JCE.DivCHED.org
Part A
Consider the thermodynamics of the hypothetical pro-
cess.
H2O(l) → ice-nine(s)
1. Based on the information above, will ∆GЊ for the formation
of ice-nine from liquid water be positive (+) or
negative (−)? Explain how you know.
2. Will the entropy, SЊ, for the system (the ocean) increase
or decrease for this process? Explain how you know.
3. Based on your answers above, will the enthalpy change,
∆H Њ, for this process be positive (+) or negative (−)?
Write an equation to support your answer.
4. In the story, the author makes no mention of any temperature
change that occurs when the entire ocean
“froze” to ice-nine. Based on your answers above, is it
necessary that the temperature of the ocean and its surroundings
change as the liquid water is converted to icenine?
Explain.
5. Given that the melting point of ice-nine is much higher
than that of regular ice, will the ∆HЊ for the conversion
of water to ice-nine be more positive or more negative
than the ∆H Њ for the conversion of water to regular ice?
Does ice-nine have stronger or weaker intermolecular
attractions than regular ice? Explain.
Part B
6. The melting point of ice-nine is given as 114.4 ЊF. What
is the melting point of ice-nine in Celsius degrees?
7. If 1.00 mol of water at 0 ЊC were converted to ice-nine,
what is the minimum quantity of heat that would be
released? (The enthalpy of fusion for regular ice is 6.01
kJ͞mol.)
8. Imagine 1.00 mol of water being converted to ice-nine
in an insulated container. Liquid water has a heat capacity
of 4.184 J͞(g ЊC). Since liquids generally have a
higher heat capacity that their corresponding solids we
can make the assumption that the heat capacity for icenine
would not be more than 4.184 J͞(g ЊC). Given the
minimum quantity of heat released when 1.00 mol water
is converted to ice-nine (step 7 above) and our assumption
about the maximum heat capacity of ice-nine,
calculate the temperature change that would have to result
from the conversion of 1.00 mol liquid water at 0 ЊC
to ice-nine in an insulated container. Is this possible?
9. If we imagine that ice-nine really existed, is it possible
that the ocean could be “instantly” converted into icenine
as described by the author? What other changes
might need to take place?
Discussion
After the students have had an opportunity to think
about the questions in Part A and discuss them in small
groups, we come together as a class to defend our answers.
From the information given, most students are able to determine
that the formation of ice-nine is a spontaneous process
(in the story) and that the ∆GЊ for the process must be
negative. From previous discussions on entropy changes associated
with changes of state, most students remember that
in going from a liquid to a solid, the entropy of a system
decreases, and ∆S Њ for the formation of ice-nine from liquid
water (in the ocean) would be negative since solids are inherently
more ordered than liquids. Given that the process
is spontaneous and that the entropy change is negative, students
can then reason that the ∆H Њ must be negative as well.
This is easily shown from the Gibbs function,
∆GЊ = ∆H Њ − T∆S Њ. If ∆S Њ is negative, the only way for
∆GЊ to be negative is if ∆H Њ is negative as well. This idea
can be reinforced in the discussion with the saturated sodium
acetate demonstration. A stoppered flask containing newly
solidified sodium acetate, made by dropping a seed crystal
into a flask of supersaturated sodium acetate (5), is passed
around so that the students can feel for themselves that this
related process is exothermic. A commercial hot pack could
suffice here as well.2
Once the formation of ice-nine is shown to be exothermic,
it should follow that the process must be accompanied
by an increase in temperature since this is how we define an
exothermic process. This is not necessarily obvious to the students
since many of them associate the formation of ice with
getting colder. Indeed, room temperature water, when placed
in a freezer, gets colder and freezes but the freezing process is
exothermic and will not occur unless the freezer removes the
heat.
The discussion is also used to review intermolecular interactions.
Since ice-nine is a solid at room temperature and
has a higher melting point than regular ice, it can be deduced
that the intermolecular interactions that hold the water molecules
to each other in ice-nine must be stronger than the
intermolecular interactions holding water molecules together
in regular ice. This would also mean that the enthalpy of fusion
for ice-nine must be greater than the enthalpy of fusion
for regular ice since the enthalpy of fusion results from these
intermolecular interactions.
After discussing the qualitative aspects of the change in
Part A, the students then consider a few calculations for the
process in Part B. We begin with a simple temperature conversion
problem by converting the reported melting point
of ice-nine from 114.4 ЊF to 45.78 ЊC.
Once it is shown that the ∆H Њ for the conversion of
liquid water to ice-nine is more negative than ∆H Њ for the
conversion of liquid water to regular ice, a lower limit on
the quantity of heat released in the process can be estimated.
The enthalpy of fusion for water is 6.01 kJ͞mol so the conversion
of 1.00 mol of liquid water to ice-nine will release at
least 6.01 kJ. For simplicity, the students are asked to consider
what would happen if 1.00 mol water were converted
to ice-nine in an insulated container. We can calculate a lower
limit on the temperature increase that this process would need
to produce if we make the assumption that the specific heat
capacity for ice-nine would not be greater than that for liquid
water, 4.184 J ЊC᎑1 g᎑1. This assumption is, by necessity,
pure speculation but not unreasonable since liquids tend to
have higher heat capacities than their corresponding solids
(6). Given this assumption and the lower limit to the ∆H Њ
for the process, we can calculate that the conversion of 1.00
In the Classroom
www.JCE.DivCHED.org • Vol. 81 No. 4 April 2004 • Journal of Chemical Education 511
mol (18.0 g) liquid water to ice-nine in the insulated container
would need to be accompanied by a temperature increase
of at least 79.8 ЊC!3
Even if the temperature of the
water started out at 0 ЊC, this would put the temperature in
the container above the melting point of ice-nine.4
Clearly,
the complete conversion of liquid water to ice-nine could not
occur unless a large quantity of heat was transferred to the
surroundings. If the ocean were to be converted to ice-nine,
the atmosphere would certainly need to warm considerably.5
It may be helpful, particularly for the more advanced
students, to discuss the reasonableness of this estimation of
the temperature increase. First, the physical changes discussed
above are for substances that are not in their standard states
and the phase transitions do not occur at constant temperature
and pressure. As we are making generalizations and estimations,
this should not affect our conclusions. Since the
enthalpy for the conversion of liquid water to ice-nine is likely
to be more negative than the enthalpy for the conversion of
liquid water to regular ice and the heat capacity of ice-nine
is likely to be less that that for liquid water, as discussed above,
our estimated temperature increase is merely a lower limit
on what might be expected for such a process. A higher enthalpy
or a lower specific heat capacity would each result in
a larger estimated temperature increase. Our estimation ignores
the fact that heat capacities generally increase with temperature
although the change is usually small for a narrow
temperature range (6). Taking an increased heat capacity at
higher temperature into account would bring our estimated
value down slightly.
In considering whether or not the author’s description
of the formation of ice-nine is reasonable from a thermodynamic
point of view, we could make a few conclusions. Since
the author makes a visual description of the surface of the
ocean being converted to ice-nine we can deduce that either
the entire ocean was converted to ice-nine or that only the
surface of the ocean was converted to ice-nine, which would
then require that ice-nine be less dense than liquid water. It
could be pointed out that the majority of solids are more
dense than their corresponding liquids (regular ice is an exception)
so that if ice-nine were to float it would be unusual
in that respect. Also, if ice-nine were less dense than liquid
water, the transition from liquid water to ice-nine would require
an increase in volume. The author gives no indication
of any shock waves or earthquakes that accompany the transition
indicating that there were no significant changes in the
volume of the ocean. There is the mention of the tornadoes
formed that would indicate that a tremendous quantity of
energy was somehow transferred to the atmosphere. It is certainly
reasonable that rapidly heating the atmosphere could
cause tornadoes. As stated above, the formation of ice-nine
from room temperature water is not possible without a large
quantity of heat being transferred to the surroundings. A great
deal of the heat released could also be transferred into the
ocean floor. If only the surface of the ocean were converted
to ice-nine, much less heat would be released and the liquid
water underneath could absorb a great deal of it. In any case
the conversion of liquid water to ice-nine will release a great
deal of heat that will eventually be transferred to the envi-
ronment.
Conclusion
I have used this example in both my regular second semester
introductory course as well as in my accelerated general
chemistry courses. I cover the qualitative aspects of the
discussion (Part A) with all my students and I am able to
have a much deeper discussion (Part B) with groups of stronger
students. The exercise requires from 15 to 30 minutes
depending on student interest. In general, the students come
up with reasonable answers but occasionally need a bit of
guidance. I have found this discussion to be well received
and some students are particularly enthusiastic about the discussion.
It is quite rewarding when a student says, “ I want
to go read this book” or “this is the example that made thermodynamics
stick in my head”.
This example provides an opportunity to review thermodynamic
concepts and apply them to a new situation. By
using minimal information and consistently applying the
theory, one could conclude that if ice-nine were to spontaneously
form as described in the story, its formation must be
accompanied by a very large increase in the temperature of
the ocean and its surroundings. This example demonstrates
the universality and the tremendous predictive power of thermodynamics.
In addition, the discussion allows the students
to see chemistry in relation to other disciplines such as lit-
erature.
Acknowledgments
The author wishes to thank Cornell College for its support
in developing this exercise. Truman Jordan was helpful
in the preparation and critical reading of the manuscript.
WSupplemental Material
The student assignment is available in this issue of JCE
Online.
Notes
1. The scientist in this story is the fictitious inventor of the
atomic bomb and is portrayed as rather cold and impersonal, showing
no regard for the lives destroyed by his inventions. The writings
of Vonnegut, referenced below, reflect common stereotypes of
scientists and shed important insight on the relationship of science
and society. The discussions of the thermodynamic example above
might also be used as a lead-in to the discussion of these other important
topics, which are often ignored in science courses.
2. This is the basis of a commercial hot pack in which a supersaturated
solution of sodium acetate is seeded to produce the
heat. The pack can be reused by placing it in boiling water and
heating it until supersaturation is reestablished. More information
can be obtained on http://jchemed.chem.wisc.edu/JCESoft/CCA/
CCA3/MAIN/ACETATE/PAGE1.HTM (accessed Jan 2004).
3. A standard equation for heat capacity q = mcs ∆T (where q
is the heat transferred, m is the mass, cs is the specific heat, and T
is temperature) can be rearranged to ∆T = q͞(mcs ). Taking 1.00
mol of water with a mass, m = 18.0 g, 6.01 kJ for q, and a specific
heat of 4.184 J ЊC᎑1
g᎑1
we can calculate a ∆T of 79.8 ЊC for the
complete conversion of the water to ice-nine.
In the Classroom
512 Journal of Chemical Education • Vol. 81 No. 4 April 2004 • www.JCE.DivCHED.org
4. Alternately, we could calculate the amount of the sample
in the insulated cup that would freeze if all of the heat released
went into heating the contents of the container from 0 ЊC to the
melting point of ice-nine, at which point the freezing process would
cease. Warming the sample from 0 ЊC to 45.78 ЊC would require
18.0 g × 45.78 ЊC × 4.184 J ЊC᎑1
g᎑1
= 3448 J. This is the quantity
of heat that would be released when 3448 J × 1 mol͞(6010 J) =
0.5736 mol water (10.32 g) had been converted to ice-nine. Since,
as discussed above, 4.184 J ЊC᎑1
g᎑1
, the heat capacity of liquid water,
is the upper limit on the heat capacity of ice-nine and 6010 J
is a lower limit on the enthalpy of fusion, this estimate is an upper
limit on the amount of the 1.00 mol sample that could be converted
to ice-nine without the presence of some form of a heat sink to remove
the tremendous quantity of heat released by this process.
5. If all of the heat released from the conversion of liquid water
to ice-nine were transferred to the atmosphere, an even more dramatic
temperature increase would occur. The following estimate
was suggested by a reviewer: If the ocean contains 35 million cubic
miles of water = 1.4 × 1023
mL water = 8.1 × 1021
mol, the water
would lose (8.1 × 1021
mol)(6010 J͞mol) = 4.9 × 1025
J heat. If
the troposphere were 9 miles deep and had a volume of 1.8 × 1010
mi3
= 7.5 × 1022
L, there would be 4.6 × 1021
mol of gas (assuming
a uniform pressure of 1 atm and a uniform temperature of 200
K). Assuming a heat capacity of 29 J͞(mol K) (heat capacity of
nitrogen gas) would give a temperature increase of 370 ЊC. This
estimation is offered as a dramatic example of the tremendous quantity
of heat involved in the conversion of liquid water to ice-nine.
Since heat flows from higher temperature to lower temperature, the
newly formed ice-nine would not be able to heat the atmosphere
to a higher temperature than the ice-nine itself reaches.
Literature Cited
1. (a) Hudson, R. L. J. Chem. Educ. 1987, 64, 1039. (b) Lang,
F. T. J. Chem. Educ. 1990, 67, 277.
2. (a) Labianca, D. A.; Reeves, W. J. J. Chem. Educ. 1982, 58,
683. (b) Chemistry and Science Fiction; Stocker, J. H. Ed.;
American Chemical Society: Washington, DC, 1998.
3. Vonnegut, K., Jr. Cat’s Cradle; Delacorte Press: New York,
1963; p 185.
4. Vonnegut, K., Jr. Wampeters, Foma & Granfalloons; Dell Publishing
Co.: New York, 1974; p 96.
5. Summerlin, L. R.; Ealy, J. L. Chemical Demonstrations: A
Sourcebook for Teachers; American Chemical Society: Washington,
DC, 1985; pp 28–29.
6. (a) Steiner, L. E. Introduction to Chemical Thermodynamics;
McGraw Hill: New York, 1948; pp 53–67. (b) Levine, I. N.
Physical Chemistry, 4th ed.; McGraw-Hill: New York, 1995.