LE CHATELIER
OR BUST?—OR WHY
DOOMSDAY SCENARIOS ARE ALWAYS WRONG
by Dr. David J. Goodwill
SUMMARY: This paper argues that Le Chatelier’s Principle may be
extended beyond simple chemical equilibria and applied to a wide variety of everyday
situations involving systems that are in equilibrium. Because such systems always
compensate when a stress is applied, their equilibrium seldom breaks down completely.
The author goes on to propose a corollary to Le Chatelier’s
principle that would extend it’s scope. This has been called "The Goodwill
Overshoot Principle".
Applying these two principles to key environmental matters of the day
like the earth’s atmosphere, and in particular to global warming, might suggest that
the likely outcome could actually be a mini ice age and not the more intuitive
alternative.
Introduction
In 1884, the French industrial chemist, Henri-Louis Le Chatelier (1850-1936), in
commenting on chemical systems in equilibrium1 observed that :
"When a stress is applied to a system in equilibrium, the system
will change so as to undo or offset the effect of the stress".
He enunciated this principle to describe the changes that occurred in
chemical reactions at equilibrium when external changes were made to the concentration of
the components of the reaction or to temperature or pressure.
It is being argued here that this principle has much wider relevance and
may be applied to a wide range of everyday situations and, in fact, to any system in
stable equilibrium including among others to environmental systems in the political,
cultural, scientific, technical, economic and physiological arenas. Furthermore, it will
be shown to provide a very useful analytical and predictive tool.
Le Chatelier’s Principle was applied to systems in equilibrium. A
system is said to be in stable equilibrium if after a small perturbation is applied
to it, it returns on its own to its original equilibrium state. A simple example of a
system in stable equilibrium would be a ball at the bottom of a curved bowl. When the ball
is deflected from the bottom of the bowl, other things being equal gravity will always
bring it back to the bottom center of the bowl. It should be noted that not all systems in
equilibrium are stable. A simple example of a system in unstable equilibrium would
be a pencil balanced on its point. Any small deflection will cause the pencil to fall
over. The fallen pencil will be in a very different equilibrium state from when it was
balanced on its point and so the original equilibrium was unstable. Le Chatelier’s
Principle, as originally enunciated, did not require the system to return to its original
equilibrium. Nor are we requiring that here. However, it has to be said that it is likely
that the application of Le Chatelier to situations outside of the chemical equilibria, to
which it was originally applied, is only likely to prove to be valid where relatively
small stresses and perturbations are being applied to the system in question.
A system in equilibrium is comprised of a number of inputs and outputs
that have achieved a "balanced" state. In many everyday situations, the systems
will be very complex and the inputs and outputs may be numerous. Because of this, a system
under stress will not necessarily return to its original equilibrium state but may well
return to a different one. What Le Chatelier says is that the system will respond by
resisting the changes and try to retain its original equilibrium state or at best achieve
a slightly changed equilibrium state.
Most everyday situations that we encounter are systems in some form of
equilibrium. If they were not, we would not view them as a system at all since they would
be changing continuously. We shall now go on to examine several examples of where Le
Chatelier provides added insights into real life situations.
An Economic Example—The Oil Crisis of 1976
Le Chatelier’s Principle can be a very powerful predictive tool. A good
example of the power of Le Chatelier in a situation where it was not used but should have
been relates to the period just after the oil crisis of 1976.
At that time, the author was the Group Strategic Planner for an
international holding company that had significant interests in polymers and plastic
products. On this holding company’s board was a non-executive director who was also a
director and main board member of one of the world’s leading international oil
companies. This so-called industry expert made a presentation to our board immediately
after the oil crisis predicting a Doomsday Scenario whereby the price of oil, and hence
polymers that are derived from petrochemicals, would continue to escalate for the next
decade or two along with massive and continuing inflation. His projections were based on
limited oil resources and unrestrained population growth. As a consequence, demand for oil
continued to increase over time and soon outstripped production and supply, as the known
and available oil resources of the world got used up. He argued that we might therefore
expect the trend towards higher oil prices to get steadily worse in the future. This was
indeed a very grave economic scenario for our business.
However, this pessimistic forecaster clearly had no knowledge of Le
Chatelier. He ignored the fact that when you apply a stress to a system in equilibrium,
the system adjusts so as to undo or offset the effect of the stress.
Let us examine the three main factors involved here, or the inputs to
the system , so called. These three inputs are:
- oil consumption and demand
- population growth
- oil supply and sources of supply
First, as the price of oil went up, this provided a compelling need for
change. Everyone had to get more efficient and use less oil. That is exactly what
happened. Cars got smaller and more efficient by design, insulation on houses was
improved, factories used less fuel in their processes, etc, etc. All of this was due to
human initiatives in response to high energy costs backed by government that had an eye on
balance of payments and the need to control cash outflows to purchase oil from the small
number of countries who at that time controlled crude oil. Secondly, the rate of
population increase in the developed countries, who were the big oil users, slowed due to
the unfavorable economic circumstances that people were experiencing. Families got smaller
as people had less children. Lastly, and perhaps most important of all, it became
increasingly economic to explore for new sources of oil and natural gas and new sources of
power. As a direct consequence, nuclear, solar, wind, and wave power were developed, and
vast new and as yet untapped oil resources were found, not least among which were those in
the North Sea, Alaska, etc. We now know that we have an almost unlimited supply of oil and
natural gas, at least for the foreseeable future.
The author argued with the oil industry expert at the time that his
extrapolations of population growth, oil usage and supply limitations were
over-simplistic. Judicious use of Le Chatelier would have predicted all of the above
changes and that the Doomsday Scenario would be avoided by the establishment of a new but
not very different equilibrium between oil demand and supply. This is a good example of
how to examine the main inputs to a system in equilibrium in an attempt to understand how
they might change in response to the stress being applied so as to maintain a state of
equilibrium. Fortunately, the board did not buy the scenario being presented by the
expert. If it had, it would have over-reacted unnecessarily, which might have had dire
consequences on the businesses under its control.
A Humanitarian Example—World Population Expansion
For years, we have been hearing Doomsday Scenarios about a world population
explosion. This is a particularly good example for Le Chatelier to debunk because the
logic is relatively straightforward. The planet earth is a closed ecosystem from the point
of view of population change. There are only three key input variables involved in
establishing an equilibrium situation in earth’s population: births, life expectancy,
and deaths. If the population gets too high, countries’ governments can apply rules
and laws to slow down the number of births as they have done, for example, in China. Here,
in response to runaway population growth, the Chinese government enacted a law making it a
punishable offence for a couple to have more than one child. We all know that people in
western society are living longer. We would not wish to stop progress here. But if all
else fails, we can rely on death to maintain the equilibrium for us. People will starve in
countries where their numbers have become economically unsupportable. Or diseases such as
the plague, smallpox, AIDS, SARS, etc. will spread rapidly among overcrowded populations
and cull the numbers. One way or another, the earth’s population will be controlled
to fit our planet’s limited resources. We can affect to some extent the outcome and
the means by which this is achieved providing that we are smart and can coordinate our
activities among all peoples of the earth.
A Physiological Example—Hormesis
An interesting physiological example that would appear to support Le Chatelier is hormesis.
This is the phenomenon whereby exposure to small concentrations of toxic chemicals and
pollutants has been observed actually to make humans and other living things stronger and
more resistant to infection or sickness. These observations also gave rise to the medical
practice of homeopathy, which holds that diseases may be treated by stimulating the
body’s natural defences with toxins that cause similar symptoms. However, this is a
somewhat different concept and will not be pursued here.
Hormesis is believed by Calabrese2, a foremost proponent of
the phenomenon, to be due to homeostasis, the process whereby a living organism tries to
maintain equilibrium with its environment. Thus, the immune system responds to infection
by becoming more active. When we are hot, we perspire. When we are exposed to a lot of
sun, our skin darkens, etc. The body overcompensates to small perturbations in the
environment and achieves a new and healthier equilibrium state. It would appear that our
bodies are well aware of Le Chatelier’s Principle.
Environmental Example—The Earth’s Atmosphere
We can use Le Chatelier to try to analyze and predict the outcome of other situations that
affects us all. One such is actually occurring right now, where the equilibrium is already
under significant stress. This involves the earth’s atmosphere and global warming.
The stress here is being produced by our releasing into the atmosphere ever increasing
amounts of carbon dioxide and other waste gases. These end up as a layer in the upper
atmosphere and lead to the well-known "greenhouse effect" . This results in the
average temperature of the earth’s surface rising slowly. The impact of this if it
continued unabated would be catastrophic to the earth. Among the other bad things that
could happen, the ice caps would melt and large areas of the earth would become flooded.
Also, we would get major changes in climate, etc.
Let us again first examine the inputs to the system. The increase in
waste gases is due to our cutting down the rain forests, burning more fossil fuels and
producing more pollution, and by the reduction in micro-organisms in the sea that are now
known to contribute greatly to the recycling of carbon dioxide into oxygen for us to
breathe. The sort of reactive changes that we might expect to see to offset this stress
and thus to sustain equilibrium and avert disaster are as follows:
- We stop polluting the planet at the same rate (if we are intelligent and
can learn to act together in a concerted fashion). Clearly, this change requires human
intervention and, once again, cooperation among all nations.
- As the seas warm up, more evaporation occurs producing more cloud cover
and less warming of the planet’s surface. This change is, in effect, a
self-correcting mechanism and is truly in the spirit of Le Chatelier, as is 3 below.
- Warmer average temperatures cause the ice to melt in the polar regions
and the seas to rise. This causes climate changes and higher average rainfall leading to
increase in plant cover on the land and more micro-organisms in the oceans.
These are just some of the factors that can be argued might reduce the
carbon dioxide build-up and reduce the effect of the stress being applied to the system,
which in this case is our planet’s environment. Le Chatelier’s Principle would
argue that these and other changes will occur and will tend to restore the earth’s
environmental equilibrium. Indeed, the more extreme climatic conditions that are currently
being experienced at various points of the globe could be evidence that the earth’s
climatic equilibrium is already responding by attempting to offset the various atmospheric
stresses that we are putting on it.
Other possible equilibrium restoring mechanisms are also possible. The
point of this article is not to identify all such, nor is it to suggest that we should be
complacent. Clearly in the case of the oil crisis, significant human intervention was
required in order to maintain that equilibrium. This took the form of government controls
and legislation, exploration, research and development, and significant financial
investment by individual business enterprises. These were just some of the responses among
the many initiatives that the stress being applied to the system in equilibrium brought
about.
A Corollary to Le Chatelier
We should add a corollary to Le Chatelier’s Principle. This will be called "The
Goodwill Overshoot Principle". It states simply that:
In the absence of sufficient damping force, when a system in
equilibrium is put under stress, the offsetting changes that occur, following Le
Chatelier’s Principle, will likely overcompensate before equilibrium becomes
re-established, i.e. the system will "overshoot".
This was manifest in the economic example cited above following the oil
crisis of 1976 and, indeed, would seem to be the very essence of hormesis, where the body
benefits from this overreaction by actually becoming stronger following exposure to
controlled doses of toxins or infection.
It is also likely to be a factor in global warming. Here, ironically,
The Goodwill Overshoot Principle would, in fact, predict "global cooling" rather
than the more fashionable "global warming", together with the possibility of a
mini ice age as a consequence. We shall need to wait to see what actually happens. The
point here is that, as with the oil crisis of 1976, there are many factors to be
considered including Le Chatelier. Over-simplistic predictions will be wrong.
Conclusions
The purpose of this article is simply to point out that the equilibria we find in
everyday systems are formed from fairly complex sets of inputs and outputs and that Le
Chatelier’s Principle applies just as well to these situations as it did to the
chemical equilibria for which it was originally prescribed. It should always be considered
when evaluating the possible impact on the equilibrium of a system from stresses applied
through changes to one or more of the input variables. Doomsday Scenarios are nearly
always wrong because they do not take Le Chatelier into account.
Furthermore, and as a direct consequence of Le Chatelier’s
Principle, if in doubt it can be argued that it is usually safer to assume that a system
that exhibits stable equilibrium is more likely to self-correct when small stresses are
applied to it than it is to become unstable or to bring about fundamental changes to the
system. Le Chatelier gave us this important piece of scientific observation and
understanding, albeit in the limited area of chemical reactions.
Also, we can extend the usefulness of Le Chatelier by adding a
corollary, namely The Goodwill Overshoot Principle which states that in adapting to a
stress, a system in equilibrium usually overcompensates in an attempt to sustain that
equilibrium. This will help in using Le Chatelier as a predictive tool when examining
environmental systems in equilibrium and under stress.
References
- Henri-Louis le Chatelier, Comptes rendus., 99: 786-789 (1884). Journal of
the French Academy of Sciences.
- Will Hively, "Is Radiation Good for You", Discover, December
2002.
