MATSEC SEC Core Science common mistakes
MATSEC SEC Core Science · Understand the traps and how to avoid them.
When a question says 'explain', the candidate writes a one-line fact such as 'because it is a good conductor' and moves on, giving no mechanism, no link between cause and effect, and no scientific term from the syllabus.
Candidates revise by memorising single facts and never practise turning a fact into a chain of reasoning; under time pressure they write the shortest answer that feels true, and they do not realise that 'explain' and 'describe' are marked differently from 'state'.
What to do instead
Before writing, underline the command word and count the marks: a 3-mark explain needs roughly three linked points. Practise converting facts into 'because → so → therefore' chains, e.g. 'copper has free electrons (1) that can move through the metal (2) so charge flows easily (3)'. Check each answer against the mark allocation before turning the page.
The candidate leaves the final answer in the working units or forgets to convert, e.g. writes 350 for a distance in metres when the data were given in centimetres, or writes 0.5 for a percentage.
Working memory is loaded by the calculation itself, so the unit conversion step is dropped; candidates also copy the first number they see without checking the unit printed beside it.
What to do instead
Adopt a fixed routine for every calculation: write the formula, substitute with units attached, convert to SI before substituting, then state the unit in the final line. Do a 'unit sanity check' at the end - a person cannot walk 350 m in 5 s, a current of 0.5 A is plausible but 0.5 mA may not be.
The candidate writes the symbol equation or word equation with unbalanced atoms, or omits state symbols when the question asks for them, e.g. H2 + O2 → H2O.
Candidates treat the equation as a label for the reaction rather than a quantitative statement; balancing is seen as a cosmetic step, and state symbols are memorised separately and forgotten under pressure.
What to do instead
Balance by counting each element on both sides and adjusting coefficients only, never subscripts. Practise a five-step drill: word equation → correct formulae → balance → add (s), (l), (g), (aq) → check atom count again. Include one ionic equation per revision session so the charges are also balanced.
When asked to describe a trend or interpret a graph or table, the candidate copies individual data points ('at 20 °C it was 4, at 30 °C it was 7') instead of stating the relationship and quoting figures as evidence.
Candidates believe quoting numbers is what 'using the data' means; they have not been taught the difference between reading a point and describing a trend, and they avoid comparative language in case it is wrong.
What to do instead
Use the pattern 'As X increases, Y increases/falls, at first rapidly then levelling off; for example, from 20 °C to 30 °C Y rose from 4 to 7.' Name any anomaly separately and suggest a cause. Practise on past-paper-style tables until the trend sentence comes first and the numbers second.
In experimental-design questions the candidate lists apparatus but omits the controlled variables, the repeat/mean step, or a safety precaution, and describes a method that cannot actually test the stated hypothesis.
Candidates recall the practical they did but not the logic behind it; they confuse 'what I used' with 'how I made the test fair', and they do not link each design choice back to the variable being changed and measured.
What to do instead
Answer with a fixed skeleton: hypothesis → independent variable → dependent variable and how measured → at least two control variables held constant → number of repeats and mean → safety. Say explicitly 'I keep X the same because otherwise it would also affect Y', so the marker sees the reasoning, not just a list.
The candidate uses everyday words where the mark scheme requires the scientific term, e.g. 'the blood goes round' instead of 'circulates', 'the plant makes food from light' without naming photosynthesis, or 'the force pushes back' instead of 'reaction force'.
Candidates understand the idea and assume the marker will accept the plain-language version; vocabulary is revised passively by reading rather than actively by recall, so the precise term is not available when writing.
What to do instead
Keep a running glossary per topic and test yourself by writing definitions from memory, not by re-reading. In every practice answer, circle any word that could be replaced by a syllabus term and replace it. Learn the standard phrasing for key processes (diffusion, osmosis, photosynthesis, respiration, neutralisation) as complete sentences.
The candidate answers a question about a familiar context with a memorised answer for a different context, e.g. applies a series-circuit rule to a parallel circuit, or assumes 'osmosis' whenever water moves, even when a partially permeable membrane is absent.
Revision is organised by topic and by example, so the candidate pattern-matches on a keyword rather than reading the actual conditions in the question; unfamiliar contexts feel like a trick and trigger the nearest memorised answer.
What to do instead
Before answering, write down the conditions the question actually states (membrane present? components in one loop or branches? closed system?). Then choose the rule that matches those conditions. Deliberately practise the same concept in two or three different contexts (a plant root, a potato chip, a red blood cell) so the rule, not the example, is what you recall.
The candidate writes a conclusion that goes beyond the evidence, e.g. 'this proves the enzyme is denatured' from a single temperature reading, or states a cause when only a correlation was shown.
Candidates want to show knowledge and add extra claims; they are not taught to distinguish 'the data show' from 'this suggests', and they fear a short conclusion will lose marks.
What to do instead
Use a two-sentence conclusion: sentence one states what the data show, with a figure; sentence two states a limitation or a further test needed. Learn the phrase 'this suggests … but further data are needed to confirm …'. Never introduce a mechanism in the conclusion unless the question asked for it.
The candidate leaves multi-part questions partly blank, spends too long on an early high-mark question, or writes answers in the wrong numbered space so parts are misaligned.
Candidates do not budget time against marks, panic when one part is hard and freeze, and under exam pressure lose track of which part of a structured question they are answering.
What to do instead
At the start, note the total marks and allow roughly one minute per mark, leaving five minutes to check. If a part stalls for more than a minute, write the best partial answer, mark it, and return later - never leave a blank where a definition or unit could earn a mark. Tick each part number as you finish it and check alignment before moving on.
The candidate gives answers with no units, too many or too few significant figures, or a numerical answer with no indication of method, so a correct final value still loses marks.
Candidates see the final number as the whole answer; they do not know that method marks are awarded for the formula and substitution, and they have not decided in advance how to round.
What to do instead
Always show three lines: formula, substitution with values, answer with unit. Round only at the end and match the precision of the data given (usually two or three significant figures). In revision, mark your own work against the mark allocation and highlight where method marks were available but not shown.