As a discipline, Chemistry has lots of jargon, needed to describe Chemistry-type things. “Amphiprotic” comes to mind.1 We can help students understand the origin of this term, but that’s not the point I want to make.
I have noticed, over the course of >36 years in this business, that students’ English vocabulary isn’t what it used to be.
They need help with words.
And we can help students by routinely explaining the English words that we use. Like it or not—we need to be English vocabulary teachers.
Here’s a good place to start—assume nothing. To you, the meaning of a word may be obvious; to a student maybe not-so-much . . .
Allow me to cite several examples from 11 and AP Chemistry with which students could use some help:
1. Spectator Ions: They’re like football fans. It can be argued that they are part of the game, but they aren’t players.
2. Electron Affinity. If we explain what “affinity"2 means, students can understand the equation a whole lot better.
X(g) + e‑ → X-(g) + energy Equation 13
I tell ‘em: “I have an affinity for 60s and 70s muscle cars.”
3. After teaching Empirical/Simplest Formula, do your students think that simplest and empirical are synonyms?
4. With respect to the Electromagnetic Spectrum: What’s a spectrum?
Corollary: the Bonding Continuum. A synonym for continuum is spectrum—a range.
5. Significant—meaningful—Figures.
6. Ionization ≠ Dissociation.
An ionization reaction, represented by:
HCl(aq) + HOH(l) → H3O+(aq) + Cl-(aq) Equation 2
involves the formation of ions from neutral compounds. This type of reaction describes the reaction of strong or weak acids with water.
By contrast, a dissociation reaction, represented by
NaOH(s) 
Na+(aq) + OH-(aq) Equation 3
involves an ionic compound simply breaking apart—dissociating—into its ions in aqueous solution. The ions were already present, they simply dissociated.
I ask students if their parents have ever told them, with respect to a less-than-savoury schoolmate: “Dissociate yourself from that kid.”
7. A reaction mechanism—a pathway. Discuss the mechanism in an old-school watch—the gears, spring, etc. It’s how the watch works.
8. A polar bond or a polar molecule has internal charge separation—a slightly positive pole and a slightly negative pole. Poles are extreme ends, like the earth’s North and South Pole, or the poles of a magnet. “John and Bob are good friends, but they appear to be polar opposites.”
9. Trigonal bipyramidal: stress the trigonal and the bi-pyramidal.
10. A calorimeter is a meter—a measuring devise—to measure calories, an old-school unit of energy. Not to be confused with a colorimeter, a spectrophotometer.
11. A buffer is a “cushion” against pH change, just as a pair of goalie pads cushions the goalie’s shins. This analogy can be extended to buffer capacity: goalie pads protect from high-velocity pucks or from tomatoes thrown by disgruntled spectators—not from artillery shells.
I hope that these examples will spur you to explain words to your students whenever the opportunity presents itself. Understanding of language reduces memorization and increases understanding.
Homework: What’s the difference between discreet and discrete?
References / Notes