Some Chemistry Myths

There are a lot of things people ask about when you tell them you’re a chemist. The things people usually want to know about are are drugs (both licit and illicit), cosmetics, cleaning products, and food. Occasionally you get questions you don’t know how to even begin thinking about, but some questions you get over and over and over again. So here are few issues people ask me about.

Processed Cheese is a Molecule Away from Plastic

This is a fun one, because it shows that a lot of the misconceptions people have about things are bound up in the words they use. The terminology is everything here. An atom corresponds to a specific element, like Helium or Iron, and two or more atoms bound together is a molecule. Molecules can be very complex or very simple. Technically water is “a molecule away” from being plastic, depending on what exactly is meant by that.

Is that a meaningful way to characterize water’s similarity with other substances? The claim is “true” in the sense that a window is a few construction workers and a lumberyard away from being a house.

But, let’s be generous here and assume what is meant is that the cheese has a similar chemical structure to plastic. Well, cheese is a mixture of a lot of different substances, but let’s narrow it down to the substances that most looks like plastic:

pplinol

The top structure represents a plastic we all know: polypropylene. You find it in the caps on soft drink bottles. The bottom is a fatty acid found in all sorts of cheese, including processed cheese. Each “kink” in the line represents a carbon atom and each line represents a carbon-carbon bound. Two lines represent double bonds, and at the tail of the linoleic acid is are a hydrogen and two oxygens. If you look at it carefully, you’ll see that fat and plastic have somewhat similar chemical structures, which is why cleaning cooking oil out of a plastic bowl always seems like it takes a little longer. They’re both carbon-based polymers, meaning they have repeating units of carbon chains that make up the primary structure. Lots of things have repeating carbon units because that’s one of the many ways nature has to create complex structures like plants and animals, and you see it in petroleum, which ultimately comes from once living things.

So instead of focusing on processed cheese’s purported similarity to plastic, why not worry about its nutritional content, or how well it melts on your burger?

Glass is a Slow-moving Liquid

This misconception seems to be dying, but it’s based on the fact that old glass panes tend to be thicker on the bottom, but this has a lot more to do with old glassmaking techniques creating uneven panes. Windows were made so that the thickest and strongest part of the glass was situated towards the bottom.

Some of the misconception seems to be based on the fact that glass is amorphous. Amorphous doesn’t mean liquid, it just means there is no long-range ordered structure. Liquids are also amorphous because they lack long-range order as well. The silica molecules in glass are orientated randomy instead of forming a crystal, but it’s not a liquid.

You can Alkalize Your Body by Eating Certain Foods

No. You can’t. Your body is constantly undertaking the process of homeostasis. All of your biological processes are highly evolved to keep everything from pH to oxygen levels within a fairly narrow range. This is more biology than chemistry, but consider what happens when you drop anything alkaline into your highly acidic stomach: It doesn’t stay alkaline. Your body constantly generates stomach acid and enzymes no matter how many “alkaline” foods you eat, because your body uses energy and nutrients to make stomach acid–you don’t supply it through eating acidic foods. The reason I put “alkaline” in scare-quotes is because this myth often list foods that are decidedly acidic as “alkaline.” Sometimes they’ll say something like “it forms a buffer with stomach acid.” I doubt the people saying this know what a buffer is, but again, say it with me: Homeostasis. Your stomach has a built-in buffer that it uses, based on bicarbonate, which is why antacids like Tums are bicarbonate based. Even those antacids are limited in what they can accomplish, just ask any long-term heartburn sufferer. Your body is not a beaker into which simple chemicals can control something as vital as pH, it’s a complex living thing that has been molded by millions of years of predation, fear, hunger, thirst, and selection pressures we can no longer even contemplate. Let’s show it a little respect.

It’s More Efficient To Melt/Condense Snow/Water Than it Is to Move it.

I’m cheating a little here in that I don’t actually get this in casual conversation, but I do see it shared endlessly across the Internet. Various people have started crowdfunding drives to build devices that pull water from air in areas facing drought, or alternatively have proposed that streets can be heated to remove snow in the winter. These sound like good ideas, but the reality is that they rely on poor understandings of physics and chemistry. The issue is one of changing the state of water. Whether it’s pulling water from air (condensation) or liquefying ice (melting), whenever you take water (or any substance) from one state of matter to the next, there is a huge energy cost. Perhaps at some point in the future I’ll draw up some sample calculations to prove it, but the fundamental physics often make these ideas impractical for large scale applications. Having a heated driveway that you personally pay for is absolutely feasible, but asking a municipality or state to take up that expense for miles and miles of road is a different story. It’s a waste of electricity that could be going to other things when snow-plows do an excellent, albeit imperfect, job of pushing the snow aside.

Similarly, areas that are drought stricken and in dire need of water immediately often don’t have the well-developed energy infrastructure to power devices that condense water from air. Even if they do, low rainfall correlates directly with low ambient humidity, meaning even the air is often too dry to extract moisture energetically. Efforts such as groundwater exploration, water reclamation projects, and irrigation systems are often much more economical and practical than the various “water from air” schemes I’ve seen. In fact, those efforts may do more harm than good by diverting resources from proven strategies.

Rust Spreads

There is some truth to this, but it doesn’t spread the way people think it does, like a disease. Rusting is an electrochemical reaction that happens spontaneously between metal and air, and hastened considerably by water (so much so that we say it effectively doesn’t happen without water.) The reality is that rust has a different structure than the metal it formed from. It’s brittle and prone to forming cracks. Those cracks exposed more metal to the air and elements, causing more rust to form. Unlike copper and other metals, where the oxide layer forms a protective seal around the rest of the metal, rust begets more rust by structurally breaking up the iron surface. But simply taking rust from a piece of metal and putting it on top of another clean piece of metal won’t induce rust formation. That said, wet rust may contain some iron chlorides, salts, and other substances that can start the rusting process in an otherwise pristine piece of metal.

Stopping rust from moving along a structure can be a painful process that requires removal of material. You cannot reconvert rust to metal in a way that leaves you with the original surface in tact. Instead, you have to remove the rust using acid and/or abrasive action with stiff wire brushes and sanding paper to get to the clean iron or steel surface, then, without wasting any time, it’s critical that it be painted or sealed, although certain kinds of steel are fairly resilient. Jimmy DiResta, the restorer, maker, and artist likes to use ketchup to remove light rust because in addition to its vinegar acid content, it clings to surfaces really well.

How to Remove Stains

If there is a class of question that friends and family all tend to come to with, it’s the issue of stains on beloved clothing. This one is complicated. It depends on what the stain is, what the fabric is, how long its been in the fabric, and how valuable the clothing is. Sometimes it’s easy to prescribe a solution for something simple and common like Sharpie marks, but other kinds of stains can be a little more baffling. Stains are hard even for chemists because some substances bind so well to the fabric that there is very little recourse but to attempt using a substance that stands a good chance of destroying the fabric you’re trying to save. This is the entire conceit of dyeing fabric. Some substances are excellent dyes without anyone designing them to be, such as certain types of mud. Chlorine bleach is often a good bet for certain kinds of stains that are effectively acting as organic dyes, the trouble being that a lot of clothing is colored with organic dyes, so you risk discoloration if you use bleach. Often the best resource to have for this kind of situation isn’t a chemist, but a good dry cleaner. Why?

Well, a chemist can tell you how to remove certain stains, but you might not necessarily be able to do it yourself anyway. Certain stains can be lifted off of the fabric by using organic solvents. These are often toxic, damaging to the environment, or difficult to work with. Your local dry cleaner has the licenses, waste disposal systems, and equipment necessary to do the job safely. They also have access to more conventional stain removal methods and a lot of practical knowledge about what works and what doesn’t. It’s not so much that chemists are useless here, but rather that every case is different, and unless the fabric in question is a 14th century tapestry, it’s often not worth the effort and expense of coming up with a custom method to remove a stain without harming the underlying fabric. By all means ask your chemist friends what they think, just don’t be surprised if the first thing they ask is, “Have you tried taking it to a dry cleaner?”

 

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