Criterion A: Knowing and understanding | IB MYP Sciences

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This is the criterion closest to a traditional exam, but it is not a memory test. It rewards knowing the science, using it somewhere new, and weighing evidence — in that order of difficulty.

🎯The three strands

At Year 5 the strands ask you to:

i. Explain scientific knowledge. Not just state a fact — give the mechanism, the “because”.
ii. Apply scientific knowledge and understanding to solve problems set in familiar and unfamiliar situations. The unfamiliar half is where the marks are.
iii. Analyse and evaluate information to make scientifically supported judgements. Take data or a claim, and decide what it does and does not show.

📈What moves you up the bands

A response in the 1–2 band states correct facts in situations it has seen before. A response in the 7–8 band explains the science and applies it confidently to a situation it has never met, then uses evidence to reach a judgement it can defend. The jump is not more content — it is the word because, and the willingness to reason about something unfamiliar rather than reaching for a memorised answer.

✏️In physics, concretely

Why do the bulbs get dimmer as you add more in series?

A weak, band-1–2 answer is: “Because there is more resistance.” True, but it only states.

A band-7–8 answer explains the mechanism and then transfers it:

“Adding bulbs in series increases the total resistance, so for the same battery e.m.f. the current through the whole loop falls (\( I = V/R \)). Each bulb’s brightness depends on the power it dissipates, \( P = I^{2}R \); with a smaller current, less power is dissipated in each bulb, so all of them dim together. The same reasoning predicts what happens in an unfamiliar case: if one bulb is replaced by one with a thicker filament, and so a lower resistance, the total resistance falls and the current rises, so the unchanged bulbs grow brighter — same resistance, more current, more \( I^{2}R \) — while the new low-resistance bulb, carrying that same current but with the smallest resistance in the string, is actually the dimmest of the three.”

That final sentence is what earns the top band — applying the idea to a case the question never gave you.

The mistakes that cap your level are (1) stopping at a correct statement without the mechanism, and (2) treating an unfamiliar scenario as if it were a different question and answering the familiar one instead. When a question puts you somewhere new — a circuit you have not drawn, a graph shape you have not seen — that is deliberate, and it is where strand ii is being tested. Say what principle applies and follow it through, even if you are unsure; a reasoned attempt in an unfamiliar situation outscores a perfect recall of a familiar one.

⚖️Strand iii is not the same as strand i

Analysing and evaluating means judging information, not reproducing it. Given two students’ claims about which material is the better insulator, a top response does not just say who is right — it points to the specific evidence that supports one claim, notes what the data cannot settle, and states the judgement as a conclusion the evidence justifies.

“The data support A because the temperature fell more slowly, but the test only ran for two minutes, so we cannot yet say A would still be better over an hour” is a scientifically supported judgement. “A is better” is not.

📝Practise

Criterion A practice set — to be linked.