Section 1–4 Chemical reactions

(Simple molecules / Special molecules / Human molecules)

According to Feynman, a chemical reaction is an atomic process in which there is a rearrangement of atomic partners. Furthermore, there is no sharp distinction between chemical reactions and physical processes. In this section, Feynman discusses chemical reactions that are related to simple molecules, special molecules, and human molecules.

1. Simple molecules (Carbon burning in oxygen):

“the oxygen may arrive with only a little energy, but the oxygen and carbon will snap together with a tremendous vengeance and commotion, and everything near them will pick up the energy (Feynman et al., 1963, section 1.4 Chemical reactions).”

Feynman begins with a simple chemical reaction pertaining to “carbon burning in oxygen.” Initially, a carbon atom can combine with an oxygen atom to form a molecule that is called carbon monoxide. He explains that atoms are very special and they tend to attract certain particular atomic partners: “carbon attracts oxygen” much more than “oxygen attracts oxygen” and “carbon attracts carbon.” Interestingly, he describes an oxygen atom and a carbon atom can snap together with a tremendous vengeance and commotion even though the oxygen atom had only a little energy. That is, chemical reactions generate additional kinetic energy of atoms (or thermal energy) and increase the temperature of the surrounding. In certain circumstances, it can result in flames and generate light.

In a sense, Feynman seems to suggest that the carbon atom in the carbon monoxide molecule is not satisfied with having one partner (oxygen atom). It is possible to have another chemical reaction when a carbon monoxide molecule collides with another oxygen atom. A carbon monoxide molecule can combine with another oxygen atom to form a molecule that is called carbon dioxide. Feynman adds that in a very rapid reaction where the explosion is very fast, more carbon monoxide molecules are formed instead of carbon dioxide. This can be related to an automobile engine or car when a very large amount of energy is released during these chemical reactions. However, “forming carbon dioxide” nowadays can be closely related to global warming and economic prosperity.

You may like Feynman’s further explanation of this chemical reaction during a British Broadcasting Corporation interview: “Atoms like each other to different degrees. Oxygen, for instance in the air, would like to be next to carbon, and if they get near to each other, they snap together. If they’re not too close though, they repel and they go apart, so they don’t know that they could snap together. It’s just as if you had a ball, it was trying to climb a hill and there was a hole it could go into, like a volcano hole, a deep one. It’s rolling along, it doesn’t go down in the deep hole, because if it starts to climb the hill and then rolls away again. But if you made it go fast enough, it will fall into the hole… (Feynman, 1994, p.128).”

2. Special Molecules (Odor of Violets):

“If we go into a field of small violets, we know what “that smell” is. It is some kind of molecule, or arrangement of atoms, that has worked its way into our noses (Feynman et al., 1963, section 1.4 Chemical reactions).”

Unlike the “carbon burning in oxygen,” there is no explanation on the formation of the “odor of violets.” Instead, Feynman mainly discusses the chemical structure of α-irone and how chemists find out the arrangement of atoms in special molecules by using chemical reactions. Essentially, they mix the special molecules with some known chemicals to find out whether the color of which changes to red or blue. During the British Broadcasting Corporation interview mentioned earlier, Feynman replies that, “the smell of violets is very similar to the chemical that's used by a certain butterfly … to attract all its mates? It turns out that this chemical is exactly the smell of violets with a small change of a few molecules (Feynman, 1994, p.107).” His main intention in this interview is to show that the smell of violets is still beautiful when we understand the special molecules in terms of atoms.

You can trust Feynman on chemistry because he had a great deal of experience as a working chemist when he was young. Interested students should read the section “The Chief Research Chemist of the Metaplast Corporation” in his autobiography, Surely You’re joking, Mr. Feynman! When Feynman asked Frederic de Hoffman to give his impression of the Metaplast Corporation, Hoffman guessed that it must have twenty-five or fifty chemists, and the chief research chemist has his own office (Feynman, 1997). Thus, Hoffman believed that his laboratory having only six chemists were unable to compete with the Metaplast Corporation. Hoffman might be shocked when he realized that Feynman was the chief research chemist of the Metaplast Corporation, whose staff consisted of only a bottle-washer (Feynman’s friend’s brother).

3. Human Molecules:

“all the life of a stream of water, can be nothing but a pile of atoms… When we say we are a pile of atoms, we do not mean we are merely a pile of atoms… (Feynman et al., 1963, section 1.4 Chemical reactions).”

It is controversial whether life can be essentially explained by a pile of atoms. Feynman primarily explains that atoms exist based on physicists’ deductions from Brownian motion and x-ray analysis. To be precise, Einstein’s (1905) derivation of diffusion coefficient of spherical particles (e.g. sugar) through a liquid and Perrin’s experiments in the determination of Avogadro’s number help to calculate the number of atoms. In addition, Max von Laue’s discovery of diffraction of X-rays in crystals shows that a crystal is a periodic array of atoms in 1912. Curiously, Feynman mentions that we cannot see atoms by using a light microscope or an electron microscope. However, Erwin Müller’s field ion microscope made history in “seeing” atoms on Oct 11, 1955.

Currently, biologists do not agree that behaviors of human beings (or human molecules) can be merely explained by a pile of atoms. Interestingly, Feynman asks us to imagine how a human being walking back and forth in front of us, talking to us, is a great glob of atoms in a very complex arrangement. He even ends the chapter with an intriguing statement: “[w]hen we say we are a pile of atoms, we do not mean we are merely a pile of atoms, because a pile of atoms which is not repeated from one to the other might well have the possibilities which you see before you in the mirror.” In a sense, this suggests the possibility of unique human molecules (e.g. a girl) looking into a mirror, but we should expect chemical reactions to occur during this process.

Feynman opines that the most important hypothesis in biology is “everything that animals do, atoms do.” This is sometimes known as a reductionist view in which the behavior of living things can be completely understood in terms of atoms according to the laws of physics. On the contrary, biologists would disagree with Feynman because they adopt an emergentist view in which a different property (or trait) of a composite system can be emerged from its smaller systems or constituents. In other words, they do not agree that all biological phenomena can be explained in terms of chemistry and physics. Simply put, reductionism means that the whole can be explained totally by its parts (or atoms), whereas emergentism means that the whole cannot be simply explained by the properties of its parts.

Questions for discussion:

1. Explain the phenomenon carbon burning in oxygen in terms of simple molecules.

2. Explain how scientists determine the chemical structure of special molecules (e.g. the odor of violets).

3. Explain whether chemical reactions occur when human molecules (male or female) look into a mirror.

The moral of the lesson: Life is nothing but a pile of atoms such as methane and ammonia, in which there is a continuous rearrangement of the atomic partners (or simply chemical reactions).

References:

1. Einstein, A. (1905). Über die von der molekularkinetischen Theorie der Wärme geforderte Bewegung von in ruhenden Flüssigkeiten suspendierten Teilchen. Annalen der physik, 322(8), 549-560.

2. Feynman, R. P. (1994). No Ordinary Genius: The Illustrated Richard Feynman. New York: W. W. Norton & Company.

3. Feynman, R. P. (1997). Surely you’re Joking, Mr. Feynman. New York: Norton.

4. Feynman, R. P., Leighton, R. B., & Sands, M. (1963). The Feynman Lectures on Physics, Vol I: Mainly mechanics, radiation, and heat. Reading, MA: Addison-Wesley.