Q. How can you tell the difference between a chemist and a plumber?
A. Ask them to pronounce “unionized”.
Yeah, that might work. Here are some other nifty ways to tell the difference between a chemist and a plumber.
- Ask “Are you a chemist or a plumber?”
- Observe their appearance: plumbers wear coveralls and carry large pipe wrenches; chemists wear lab coats and carry beakers.
- Where did you see them? Plumbers come to your home in trucks, then shimmy through the crawl space. Chemists are usually found in laboratories. They seldom visit your home on business and they almost never shimmy.
When asked to pronounce the word unionized, a plumber would probably say “YOON-yun-ized”, as in belonging to a labor union. Labor unions are worker advocacy groups and are present in many professions. They try to protect worker rights and settle disputes between the labor and management.
A chemist would be more likely to say “un-EYE-on-ized”. In order to understand the meaning of unionized, you have to know the meaning of ionized. A molecule or atom is ionized when it acquires a positive or negative charge. This can happen when it loses or gains electrons. We’ve talked about this before. Acids and bases can also become ionized, not by gaining or losing electrons, but by splitting into charged pieces.
Consider hydrogen chloride, HCl. In its pure form, HCl is a noxious, colorless gas. The hydrogen atom and the chlorine atom share a pair of electrons; a covalent bond. The molecule as a whole is neutral, meaning it has an equal number of protons and electrons and no net charge.
When HCl dissolves in water, it changes. The hydrogen separates from the chlorine, but chlorine keeps both of the shared electrons. This leaves the hydrogen ion bereft of electrons, resulting in an overall positive charge. The chloride ion, for its participation, acquires a net negative charge. In this way HCl splits into ions without actually gaining or losing electrons.
HCl → H+ + Cl–
The liberated H+ ions are absorbed by water molecules, resulting in the formation of another ion: the hydronium ion, H3O+. Hydronium ions are the defining characteristic of aqueous acidic solutions. Any acid, dissolved in water, will yield hydronium ions.
H+ + H2O → H3O+
Bases also react with water molecules to produce ions. Instead of hydronium ions, bases produce hydroxide ions, OH–. Consider the reaction of ammonia, NH3, a base, with water:
NH3 + H2O → NH4+ + OH–
But we’re not talking about ionized molecules, we’re talking about unionized molecules. That part’s simple: an unionized molecule is any molecule that hasn’t been ionized. Yeah, I know: I could have just said that from the start. But you’ve got to have the foundation before you can get the joke. Right?