Memorising vs understanding SPM Chemistry

“Should I memorise Chemistry or understand it?” is one of the most common questions students ask, and it hides a false choice. SPM Chemistry rewards both, but for different parts of the syllabus. Some things genuinely must be memorised because there is nothing to derive; other things collapse the moment you try to memorise them without understanding. The skill is knowing which is which, and letting each support the other. Here is how to draw that line.

What you genuinely have to memorise

Some facts have no logic underneath them at your level, they simply are what they are, and you must know them cold:

• Element symbols and common ion charges, that sodium is Na⁺, chloride is Cl⁻, magnesium is Mg²⁺, aluminium is Al³⁺, and polyatomic ions such as sulfate SO₄²⁻, nitrate NO₃⁻, carbonate CO₃²⁻ and hydroxide OH⁻. You cannot reason these out mid-exam; you build formulae from them, so they must be automatic.
• Standard test observations, the confirmatory tests for common gases: hydrogen gives a “pop” with a lighted splinter, oxygen relights a glowing splinter, carbon dioxide turns limewater chalky (milky), ammonia turns moist red litmus paper blue, and chlorine bleaches moist litmus paper. These are recall, and you can drill them with our gas tests reference.
• Indicator colours and precise definitions, litmus is red in acid and blue in alkali; the exact wording of definitions such as rate of reaction or oxidation must be reproduced accurately for the marking scheme. Keeping a running glossary of these is one of the highest-value habits in the subject.

For this category, memory techniques earn their keep: flashcards, spaced repetition, and writing the fact out repeatedly. There is no shortcut, and pretending you can “understand” your way to the charge on a nitrate ion just wastes exam time.

What you must understand, not memorise

Other topics are the opposite: trying to memorise them produces brittle, useless knowledge that fails the moment a question is phrased differently.

• The mole concept is the clearest example. If you understand that a mole is simply a fixed number of particles, the Avogadro constant, 6.02 x 10²³ mol⁻¹, and that molar mass links mass to moles while molar volume (24 dm³ mol⁻¹ at room conditions) links gas volume to moles, then every calculation is one idea applied differently. Students who instead memorise a dozen separate “formulas” for mass, volume and concentration get lost the instant a question combines them.
• Bonding is another. Once you understand that atoms gain, lose or share electrons to reach a stable electron arrangement, ionic and covalent bonding stop being two lists to memorise and become one idea with two outcomes. Our chapter on the chemical bond is built around that logic rather than rote lists.
• Redox and reactions generally follow the same rule: if you grasp that oxidation is loss of electrons and reduction is gain, you can predict what happens in displacement, corrosion and electrolysis instead of memorising each case. Browsing worked reactions with that lens turns dozens of separate equations into a few patterns.

Memorising these topics is not just harder, it actively fails you, because SPM increasingly asks you to apply ideas to unfamiliar situations, not just recall them.

How the two support each other

The real insight is that memorising and understanding are not rivals; they feed each other.

Understanding reduces how much you must memorise. Once you understand why metals sit in a particular order of reactivity, you no longer memorise every displacement result, you work it out. Understanding also makes the truly memorised facts stick, because they now hang on a framework instead of floating free; an ion charge you use constantly in balancing equations is far easier to retain than one you only ever chanted.

In the other direction, memorised facts are the raw material understanding works on. You cannot reason about a reaction if you do not know the formulae of the substances in it. Understanding without the basic recalled facts is like reasoning with missing pieces; recall without understanding is a pile of pieces you cannot assemble under pressure.

A practical rule for revising

As you revise each topic, ask one question: is there anything to understand here, or is this pure fact?

• If it is pure fact, symbols, charges, test observations, definitions, memorise it deliberately with flashcards and repetition.
• If there is a mechanism or a logic, moles, bonding, redox, rate, electrolysis, spend your time understanding the why until you could re-derive it, and memorise only the small anchor facts it needs.

Do not let anyone tell you Chemistry is “all memorising” or “all understanding”. It is a subject that punishes students who pick only one. Sort each topic into the right bin, use the right tool for each, and let your understanding shrink your memory load while your solid facts give your understanding something to work with. That balance, more than raw effort, is what separates a stressed B from a confident A.