Myths and legends: In defence of general chemistry



Elisabeth Tondl is in the second year of her PhD at the University of Sydney, investigating selective delivery of chemotherapeutics to prostate cancer. She holds two Teaching Fellowships, at The University of Sydney and The Women’s College, and is insatiably curious about the world.

There are some pretty crazy ideas on the interwebs about chemicals and how they can make you (and the environment) sick. So, as a researcher in chemistry, I’m going to contribute my 2 cents’ worth by combating some common misconceptions.
“Pure H2O is the healthiest”

This attractive legend is thoroughly undermined by an understanding of osmotic pressure. In our blood, we have lots of different molecules – proteins, sugars, enzymes and so on. For every litre of our blood, there’s a certain amount of those molecules in there (known as concentration), just as the liquid in our cells has a certain concentration.
The principles of osmotic flow tell us that water flows towards the region of highest concentration – this means, if we dilute our blood by drinking pure H2O, water will rush from our watered down blood into our very concentrated cells. Such a sudden influx causes the cells to burst and die. Next time you buy bottled water, take a look at the label telling you how much magnesium, chloride and other stuff there is in your H2O, and be glad to have averted the slaughter of your cells.
“Natural sugars are better than synthetic sugars”

This myth springs from a misunderstanding of the chemical structures of sugars, which are short-chain carbohydrates. There are lots of different kinds of sugars in our bodies and in our environment, and you’re most probably familiar with glucose (diabetics have harmfully high levels in their blood) and sucrose (edible table sugar). The point is, these sugar molecules have defined chemical structures – sucrose is the same, whether you get it from a plant, or eat it in a muffin.
Given that the chemical structures are the same, it’s really not logical to claim that “natural sucrose” from plants is any different to the white crystalline sugar you buy from the shops, or the sucrose I can make in the lab. The only difference is in whatever accompanies the sucrose molecules – other molecules that are removed in the refining process, to give you pure sucrose to stir in your coffee or tea.
“I have a chemical-free diet”

No, you don’t, unless you are living in a vacuum and never breathing, eating, or drinking anything at all (and then your body would still be making chemicals, until you died, and then it would make some more chemicals when your body decomposed). When people say this, they commonly mean that they are avoiding preservatives or foods containing compounds they know to have been synthesised in a lab (see comments on the previous myth). But I just had to mention this misconception, because as a chemist it hurts me physically to hear it, and I will go about contradicting it until I die and decompose.

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