Molecular Monday: Water Gets Freaky

After today’s post, you might never look at a glass of water the same way again.

The water molecule is made of two hydrogen atoms plus one oxygen atom, arranged in a Mickey Mouse shape, with the chemical formula H20. You already knew that, I’m sure. But you may not be aware of this: water’s chemical formula gives you a hint about water’s true nature.

Hydrogen ions play an important role in acid/base chemistry, so when you see hydrogen listed first in a chemical formula, that typically indicates that you’re looking at the chemical formula of an acid.

  • Acid: an acid is a chemical that can give up a proton (a.k.a. a hydrogen ion) to a base.
  • Base: a base is a chemical that can accept a proton from an acid.

Water can do both. It’s an acid. It’s also a base.

  • Acidic Water: a water molecule (H2O) can give up a proton to a base, transforming itself into a hydroxide ion (HO).
  • Basic Water: a water molecule (H2O) can accept a proton from an acid, transforming into a molecule called hydronium (H3O+).

Now this is where things get really freaky: because water is both an acid and a base, it can actually react with itself.

Image credit: Manuel Almagro Rivas – Own work, CC BY-SA 4.0, Link

In fact water is constantly reacting with itself. The result is that even “pure water” is really a mix of water, hydroxide, and hydronium in a proton-swapping party that never ends.

Something to think about the next time you drink a glass of water.

* * *

Today’s post is part of a special series here on Planet Pailly called Molecular Mondays.

On the first Monday of the month, we take a closer look at the atoms and molecules that make up our physical universe, both in reality and in science fiction.

3 thoughts on “Molecular Monday: Water Gets Freaky

  1. Great stuff. For something that we see so often, and is such a big part of our lives, we really don’t spend a lot of time thinking about the substance itself, do we? Ever do any reading into some of the other forms of water, for instance, the excitingly named “heavy water” (deuterium hydroxide)?

    Liked by 1 person

    1. I’ve heard of heavy water, but I haven’t done much reading about it. A while back I did some posts on various alternative forms of water ice, like the high temperature/high pressure ices that may exist inside gas giants.

      Liked by 1 person

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