Why is chemistry vocabulary harder than biology or physics?

Biology vocabulary tends to label things you can draw (cell, mitochondrion, alveolus). Physics vocabulary tends to label things you can measure (velocity, current, resistance). Chemistry vocabulary often labels things you can't directly see — ions and isotopes and electron configurations — and the labels sit very close to each other in meaning. A wobbly word in chemistry causes more damage downstream.

Should my child make flashcards?

Flashcards work well for chemistry vocabulary, but only after the concept has been taught at the particle level. A flashcard reading 'ion — a charged atom' is doing very little if the student doesn't have a Bohr diagram in their head showing why an atom would become charged. Curie's order is: concept first, vocabulary second, flashcards third.

Will Prof Curie help with chemistry homework that's all definitions?

Yes, but she'll do it the slow way. If the homework is 'define ion, isotope, and ion', she'll start by checking the underlying picture, then prompt the student to write the definition in their own words, then sharpen it to exam-quality phrasing. She won't just provide the definitions. The student writing it themselves is the part that sticks.

What's the link between Curie and Prof Quill on vocabulary?

They overlap deliberately. Prof Quill teaches English and is the master of word-level analysis. The technique he uses for unpacking a literary key word (Greek/Latin roots, near-synonyms, what it isn't) is the same technique Curie borrows for chemistry. A student learning 'oxidation' from Curie will hear ideas that Quill could have introduced — that's by design.

The KS3 Chemistry Vocabulary Cliff (And How Prof Curie Climbs It With Your Child)

There's a moment, usually in Year 9, when chemistry stops feeling like science and starts feeling like a foreign language. The maths is the same. The diagrams look familiar. But the sentences don't parse anymore. "When the magnesium ion is reduced by gaining electrons, the oxidation state changes from +2 to 0, displacing the copper from solution..." Every word in that sentence is doing definitional work. If any of them is fuzzy, the whole thing collapses.

This is the chemistry vocabulary cliff. Most students slide off it slowly between Year 9 and Year 11. By GCSE, they're nominally still studying chemistry but actually decoding sentences word by word, and getting tired before they get to the science.

Prof Curie's job is to make sure your child climbs the cliff in Year 7 to 9, while the climb is short and the consequences of a missed step are forgiving.

The five words that do the most damage

Out of the hundred-ish technical words in KS3 chemistry, five do disproportionate damage if they're shaky. They show up everywhere in GCSE and they're easy to think you know.

1. Ion

An atom (or group of atoms) that has gained or lost electrons, giving it a charge. The fuzzy version a student might have: "an atom with a charge". That's not wrong, but it's not enough — the student also needs the particle picture of why an atom would become charged (full outer shell tendency, transferring electrons in reactions). Without the picture, ionic equations are spells, not chemistry.

2. Isotope

Atoms of the same element with the same number of protons but different numbers of neutrons. The fuzzy version: "different versions of an atom". This is the one where the most students stop at the surface label without realising what's different. Curie tests this by asking: "Two isotopes of carbon. Same chemistry or different?" The right answer is same — because chemistry is about electrons, and isotopes have the same electrons. Plenty of students don't see that.

3. Mole

A counting unit for particles — 6.02 × 10²³ of anything. Strictly a GCSE concept, but Curie introduces the idea in Year 9 because it's the bridge between particle pictures and stoichiometric maths. The fuzzy version: "a really big number". The useful version: "a quantity, like 'a dozen' but for atoms, chosen so that mass-in-grams and atom-count align nicely." Get this in Year 9 and GCSE chemistry maths is half-built already.

4. Oxidation

Loss of electrons. Or, the original meaning, reaction with oxygen. The fuzzy version: "rusting". The useful version: a redox half-reaction where electrons are lost. The trap is that the historical meaning ("reacting with oxygen") and the modern meaning ("losing electrons") aren't always the same. Curie spends time on the unification — that magnesium burning in oxygen is the same kind of process as iron rusting, both can be thought of as electron loss, and the broader definition includes things that don't involve oxygen at all.

5. Displacement

A more reactive element pushing a less reactive one out of a compound. The fuzzy version: "swapping places". The useful version: a reactivity-driven reaction where one element wins, and the winner is predictable from the reactivity series. The misconception Curie watches for is the student who thinks displacement is random. Reactivity is predictable. That predictability is what makes it a useful tool.

How Curie front-loads vocabulary

The order that doesn't work: teach the topic, hope the vocabulary lands along the way, test it next term.

The order that does work, and is roughly what Curie uses:

Predict the words. Before a topic, Curie names the two or three key words about to appear and explicitly asks the student what they already think they mean. The pre-existing definition (right or wrong) is now on the table.
Build the model first. The particle-level concept is taught using the techniques in models-first chemistry. The student is not asked to use the word during this phase — just to understand the thing.
Name it. Only once the concept is grounded does Curie attach the word. "What you've just described — that thing where an atom loses an electron — chemists call that oxidation." The word now points at something real in the student's head, not vice versa.
Contrast. Curie immediately checks against the most common confusion. "Oxidation is loss of electrons. What's the opposite — and what's its name?" Reduction. The pair lives together from the start.
Paraphrase out, paraphrase in. The student writes the definition in their own words, then sharpens it to exam-style phrasing. Both versions are kept.
Spaced retrieval. The word goes on a review schedule. A week later, two weeks later, a month later. It's recalled in context — applied in a new question, not just defined.

The Quill connection

The model above is not chemistry-specific. It's how any technical vocabulary should be taught, and it's something Prof Quill (the English tutor) does for literary vocabulary. The reason they look similar is that they are similar. KS3 students who get good at this once tend to get good at it everywhere.

In a Curie session you'll occasionally hear, "the way Prof Quill would teach this word is..." or vice versa. That cross-reference is intentional. Vocabulary is a learnable skill, not a per-subject grind.

What the vocabulary cliff looks like at home

A few signals that your child is sliding off it.

They can describe a process in their own words but can't name the technical word for it.
They use a technical word confidently but can't explain it in their own words.
They confuse pairs that should be opposites: oxidation/reduction, element/compound, mixture/compound, atom/molecule.
They say "we did this in school but I don't really get it" — and the this in question turns out to be a vocabulary issue, not a conceptual one.

Curie checks for all of these in her opening probes. If any of them is firing, the session adjusts to a vocabulary-strengthening session rather than a new-content one.

What this is not

It's not a glossary lookup. Curie won't just give your child a list of words and definitions to memorise — the order matters, and the cold list is the least useful version. It's also not exam-grind. The point isn't to pass next Tuesday's vocabulary test; it's to remove the language friction that, two years from now, will make GCSE chemistry feel ten times harder than it should.

The vocabulary cliff is a structural problem in how KS3 chemistry is taught in the UK. Most schools don't have the time to do this slowly. Curie does. That's most of why she exists.

A short list to memorise (and what each unlocks)

If you want a single page to put on the fridge, here it is. The KS3 chemistry vocabulary that does the heaviest lifting:

Element / compound / mixture. The three categories of matter at the substance level. Confusing them makes the periodic table opaque.
Atom / molecule / ion. The three things at the particle level. Each does a different job.
Reactant / product. The labels on either side of a reaction arrow.
Combustion / oxidation / reduction. The reaction-type words that come up most.
Acid / alkali / neutral. And the pH scale around them.
Solute / solvent / solution. The dissolving vocabulary.

A Year 9 student who can use these confidently — in sentences, not as a list — has the chemistry literacy to enter GCSE without backfilling. That's what Curie is aiming for.

Jason runs aitutors.me. He has a Year 8 child and about fifteen years of building software adjacent to education. Updated 21 May 2026.