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Hydrogen, Nitrogen, and John Q. Public

Brian D. Rude 2004

      For a number of years now we have heard that one of these days we’ll get on a “hydrogen economy”, and that will solve our problem of fossil fuels. I’m all for it, of course. When you burn hydrogen you don’t put carbon dioxide in the atmosphere. But it seems whenever we hear, or see, or read something about hydrogen as a fuel little is said about where we’ll get the hydrogen, or, even worse, it is asserted that hydrogen is very abundant - the ocean is full of it!

      This bothers me. What does it say about the level of science education in America? It seems to me that we must conclude that the media assumes that the general public understands little more than that water is H2O, and knows nothing about the energy relationships involved. By energy relationships I am referring to the simple idea that when hydrogen burns it joins with oxygen and gives off energy, and therefore it takes an equal amount of energy to reverse the process, to separate water into hydrogen and oxygen. I like to put it this way - hydrogen is no more a source of energy than a wallet is a source of money.

      On what educational level is this bit of knowledge? I think the idea that a water molecule consists of two atoms of hydrogen joined to one atom of oxygen is not even at the level of high school chemistry. I think it is commonly learned at least by the eighth grade, and probably more like fifth or sixth grade. The energy relationship I think of as at the level of high school chemistry. That doesn’t mean the ideas involved are at the top of John Q. Public’s mind, but it seems to me that what we learn in school should’t be totally forgotten. Not everyone takes high school chemistry. When I was young probably only about 20% of the students in my school took chemistry. In my children’s generation I think that has increased considerably. It seems to me that something like 40% of the general population takes high school chemistry, and ought to have some reaction to that statement, “hydrogen is abundant - the ocean is full of it!” Even if they don’t understand explicitly that energy must be put in to get the hydrogen out, there ought to be something in their thinking that you can’t just go in the ocean and dip out buckets of hydrogen.

      Nitrogen is making the news now. At least for the moment it is. The Forum, our local newspaper in Fargo, ND, has an article in the business section of the July 4, 04 paper about a local company that is leading the way in producing nitrogen tire inflation systems. I first noticed this a few months ago when I bought a set of new tires. While waiting to have them mounted I noticed a little advertisement on the counter. You can have your tires inflated with nitrogen for the modest sum of $3 extra per tire. Then I noticed a big green machine in the shop area. Very interesting, I thought, though surely not worth an extra $3 per tire. I suspected the main advantage, surely the only advantage, is that whatever method you use to get nitrogen, you get rid of water vapor in the process. And it seems sensible that under at least some circumstances that water vapor in the tire would condense, and that’s not good for the steel wheels.

      I wondered just how the nitrogen is obtained. Does that big green machine in the shop area somehow take the nitrogen out of the air, or do they get tanks of nitrogen from some commercial producer of bottled gasses? I asked the tire salesmen who was there. He did know that the machine produced the nitrogen, there were no tanks to be replenished regularly from a commercial gas producer. Beyond that, the salesman didn’t know anything about how it worked. I figured there were two possibilities. It could be produced by a refrigeration system. I think I am correct in saying that bottled oxygen and nitrogen are produced commercially by liquifying air by compression, cooling, and decompression, and then the constituents boil off at different temperatures. Could that type of system be packaged in that green machine in the shop area? Another possibility, which I don’t understand, would be some sort of reverse osmosis. I understand that is done for distilling water now. Could that be the method used? The salesman apparently had no idea what I was talking about, so I didn’t persue the matter.

      Does the salesman’s response say much about the state of science education in America? I decided that no, it didn’t. Hopefully these ideas are touched on in high school chemistry, but they’re perhaps not that basic. Did the salesman remember anything about Boyle’s and Charles’ laws? Did he take high school chemistry? I have no way of knowing, but just judging from what clues were available I would guess that yes, he probably took high school chemistry. But that is not enough to say he should have been more curious about the workings of that big green machine. Such curiosity ought to be the result of having taken a year of college chemistry and physics. A salesman in that situation was likely to have had some college, but it’s not too likely that he was an engineering student. So, no, the salesman’s knowledge of nitrogen didn’t really tell me much about the state of science education in America, so I didn’t give it much more thought.

      But the article in the paper gave me a lot more food for thought. There was enough information there to give me some idea of the author’s knowledge of science, and his estimation of John Q. Public’s knowledge of science. I will give some quotes from the article.

      “Nitrogen is an inert, dry gas which is used in race car and airplane tires . . .. . It is also noncombustible.”

      “Tire industry analysts say nitrogen provides more consistent tire pressure, improved tread life and potentially better fuel milage.”

      “Air escapes from a tire three to four times faster than nitrogen because oxygen has smaller molecules.”

      Next in the article came some history of the idea of using nitrogen in tires, and then a section of the article titled “Why Nitrogen?” The quotes get more interesting here.

      “Traditional compressed air molecules, smaller than nitrogen, pass through tire liners and cause tires to lose air . . . ”

      “Nitrogen particles are larger and pass through tire liners 30 percent to 40 percent slower than oxygen . . . So tire pressure stays constant for a longer period.”

      “Oxygen contains moisture that causes steel tire plies to rust and weaken the tire, . . .”

      “And tires run cooler with nitrogen than with oxygen . . .”

      Nitrogen is not inert like helium, but I believe it can be said to be relatively inert, compared to oxygen or chlorine. And I assume it is dry only because any water vapor is taken out, which is probably very easy to do, compared to getting the oxygen and argon out. It’s not surprising that tire industry spokesmen would make claims for nitrogen, but the reporter mentions “tire industry analysts”. Does the reporter know the difference? Does the reporter believe these claims? Does the reporter have any basis for questioning these claims?

      I find no evidence here that the author of the article has the basic facts in mind. The basic facts I am talking about are that air consists of about 80% nitrogen and 20% oxygen, with a bit of argon, carbon dioxide, water vapor and trace amounts of other gases, and that all these gasses are made of molecules that bounce off each other causing pressure, and that when a gas is compressed the molecules are closer together and therefore collide more often causing greater pressure. I think of these facts as being taught before high school chemistry, at least by ninth grade. Anyone who takes high school chemistry ought to have the basic facts reinforced.

      The language of the article is consistent with the idea that there is such a thing as an “air molecule”, which might or might not be the same thing as a “compressed air molecule”, and that a nitrogen molecule is bigger than an “air molecule”. There is nothing to suggest that the author knows that nitrogen is the major part of air, and that tires are inflated primarily with nitrogen already, or that all gases obey the same gas laws, or that tire pressure will vary with temperature. From the article we could guess that perhaps nitrogen has nothing to do with air, but rather is a chemical that will substitute for air, perhaps made in test tubes in a laboratory.

      It appears to me that the media portrayals of both hydrogen and nitrogen indicate that the general public knows considerably less about basic science than I would have guessed that the general public knows.

      I am rather painfully aware of current trends in the teaching of math, but I know little about current trends in the teaching of science. I have heard a bit about “discovery” being stressed in science teaching in recent decades, and I know it has been popular to emphasize the role of laboratory exercises in the teaching of science, but I know nothing more than that. Is it possible that the science curriculum has become so watered down that what used to be commonly assumed to be elementary science no longer is? If children don’t learn about air and water in the elementary grades, what do they learn?

      Or, as an alternative explanation, perhaps it is only the media that are lacking in basic science knowledge. Maybe John Q. Public asks pretty much the same questions I do, but doesn’t bother to complain to the newspaper. Perhaps journalism is the problem, not science education in general.

      This brings back a memory of journalism from about ten years ago. The local television station was doing a story about the weight of women’s handbags, suggesting that women may be carrying so much weight in their handbags that they may be injuring themselves. So they weighed several handbags. One came out as “three pounds and forty-eight ounces.” Another came out as “five pounds and sixty-four ounces”. I may not have remembered the actual numbers correctly, but I believe I got the general idea right. The reporters, apparently, didn’t understand pounds and ounces.

      And speaking of math, and how well do reporters know their math? Did the writer of the nitrogen story have any problem reconciling the statement “Nitrogen particles are larger and pass through tire liners 30 percent to 40 percent slower than oxygen” with the statement “Air escapes from a tire three to four times faster than nitrogen because oxygen has smaller molecules.”

      So what are we to make of all this?