Sciency Words: Volatility

Hello, friends!  Welcome to Sciency Words, a special series here on Planet Pailly where we talk about the definitions and etymologies of science or science-related terms and expand our scientific vocabularies together!  In today’s Sciency Words post, we’re talking about:


Wow, it’s been a while since I did a Sciency Words post.  I’ve really missed writing these things.  Once I decided I was ready to bring this series back to life, I knew right away that volatility was the first word I wanted to cover.  I cannot think of any scientific term that is more frequently misused and misunderstood.

Definition of Volatility: In chemistry, volatility refers to the tendency of a chemical substance to switch from a liquid or solid state to a gaseous state.  The faster a chemical will evaporate or sublimate under ordinary environmental conditions, the more volatile that chemical is said to be.  As examples, alcohol is a highly volatile liquid, and dry ice is a highly volatile solid.

Etymology of Volatility: Words like volatile, volatility, and volatilize trace back to a Latin word meaning “to fly away.”  So you could think of it this way: the individual atoms or molecules of a volatile chemical substance are prone to “flying away” as gas.

Rather strangely for a scientific term, there is no precise mathematical definition or formula for volatility.  It’s not something you can measure, per se, but vapor pressure and boiling points are closely related concepts.  You can measure those things.  If a chemical has a high vapor pressure and/or a low boiling point, you can safely call it a volatile chemical.

As a science fiction writer who does a lot of research about science, I come across the words volatile and volatility a lot.  Most science articles—even articles written for a general audience—do not spell out what these words mean in the context of chemistry.  This can lead to some confusion.

A volatile chemical is not necessarily a dangerous chemical.  In some cases, a chemical that is volatile might also be toxic, corrosive, flammable, or explosive—or it might not.  To say a chemical substance is “volatile” or “highly volatile” simply means that chemical is prone to evaporating or sublimating under fairly ordinary environmental conditions.  That’s all.

Click here for a short article from Chemicool Dictionary titled “Definition of Volatile.”
Or click here for a video from eHow titled “Volatile vs. Non-Volatile in Chemistry.”