Botswana JCE Science (Syllabus 14) common mistakes
Botswana JCE Science (Syllabus 14) · Understand the traps and how to avoid them.
When reading a table of results, the candidate copies the value from the wrong row or column, or reports the reading for the wrong trial, so the conclusion is drawn from a number that does not belong to the stated condition.
Tables in JCE papers often have several columns of similar magnitude and a header row that wraps onto two lines. Candidates scan for a familiar-looking number instead of tracing the header down to the cell, and under time pressure they stop checking once a plausible figure appears.
What to do instead
Train a fixed reading routine: place a finger on the column heading, run it down to the required row, then read across; say the row label and column label aloud before writing the number. Practise with two-line headers and with tables where one column is a repeat trial, so the candidate must also decide which trial to quote.
The candidate writes a conclusion that goes beyond the evidence, for example claiming a fertiliser 'makes plants grow best' after measuring only one plant per concentration for one week.
School practicals reward a definite answer, so candidates learn that a confident statement scores. They do not distinguish between describing the trend in the data and asserting a general law, and they do not notice that the sample size or duration cannot support the wider claim.
What to do instead
Teach a two-sentence pattern: first state only what the data show, quoting the figures and the range tested; then state the limitation explicitly, such as the small number of plants or the short time. Mark schemes accept limited conclusions, so drill rewriting over-claiming sentences into this pattern.
When asked to identify the variable to control, the candidate names the dependent variable or writes 'keep it fair' instead of naming a specific quantity and how it is held constant.
The word 'control' is used in everyday speech to mean fairness in general, and candidates confuse the control set-up with controlled variables. They also lack practice in listing the physical conditions of an experiment and saying which ones matter.
What to do instead
Give a three-column planning frame: what I change, what I measure, what I keep the same and how. Require at least three named controlled variables with a method for each, for example same volume of water measured with a measuring cylinder. Rehearse on familiar practicals such as seed germination or dissolving.
The candidate describes a separation technique by name only, writing 'use filtration' or 'use distillation', without stating what is separated from what and what happens to each part.
Textbook diagrams are labelled with the technique name, so the name becomes the remembered unit of knowledge. Candidates do not rehearse the explanatory sentence that links the property difference, such as particle size or boiling point, to the method chosen.
What to do instead
Require every method answer to include three elements: the property difference exploited, the apparatus, and the fate of each component. For example, sand and water differ in particle size, so pouring through filter paper traps the sand while the water passes through as filtrate.
The candidate classifies a change as chemical or physical using a surface cue such as bubbling or a colour change, without checking whether a new substance has been formed, and so mislabels boiling, dissolving or a colourless gas from a fizzy drink.
Bubbles and colour changes are taught as signs of chemical change, but the same observations occur in physical changes. Candidates memorise the sign list rather than the defining criterion of a new substance, and exam wording often describes a familiar physical change in unfamiliar language.
What to do instead
Anchor the decision on one question: is a new substance formed, and is the change reversible by simple physical means? Build a sorting exercise that deliberately includes traps such as melting, dissolving, fizzing on opening a bottle, rusting and burning, and require a one-line justification of reversibility for each.
The candidate writes a word equation with correct reactants and products but ignores formulae, fails to balance atom counts when symbols are required, or writes an unbalanced symbol equation such as H2 + O2 giving H2O.
Word equations are introduced first and are accepted in many junior tasks, so balancing is practised less. Candidates also treat subscripts as decoration and do not count atoms on each side, and they write the products they expect rather than deriving them.
What to do instead
Use an atom-counting table: list each element, tally left and right, then adjust coefficients only. Give short daily drills with five equations, mixing word-to-symbol conversion and balancing, and insist that the final line is checked by recounting before moving on.
The candidate draws a food web or identifies a producer or consumer while ignoring the direction of the arrows, or describes energy flow as a cycle in which energy returns to the Sun or to plants.
Arrows in everyday diagrams show sequence, not transfer, and the phrase 'food chain' suggests eating rather than energy movement. Energy as a one-way flow with losses at each level is abstract and is often reduced to a memorised sentence without meaning.
What to do instead
Insist that every arrow is read aloud as 'is eaten by' and points from the organism eaten to the eater. For energy, draw a pyramid and write the loss at each level as heat from respiration, then ask candidates to explain why a food chain cannot loop back to the Sun.
The candidate explains a body process by naming an organ or system, for example 'the lungs breathe' or 'the kidney cleans the blood', rather than describing the transfer or change that occurs.
Everyday language uses organ names as verbs, and candidates reproduce the phrasing of textbooks without unpacking it. Junior mark schemes often award a mark for the process, so naming alone loses credit even though it feels like a complete answer.
What to do instead
Use a prompt routine: name the part, then say what enters, what leaves and what changes. For example, in the lungs oxygen passes from the air into the blood and carbon dioxide passes from the blood into the air. Practise converting organ-name statements into transfer statements.
The candidate calculates a resultant force or a speed but attaches the wrong unit, mixes up mass and weight, or reports a value with no unit at all.
Mass and weight are used interchangeably in ordinary speech, and units are treated as labels added at the end rather than part of the quantity. Candidates also copy numbers into a formula without checking whether the quantities are in compatible units.
What to do instead
Require a three-line layout for every calculation: formula, substitution with units, answer with unit. Drill mass in kilograms against weight in newtons on the Moon and on Earth, and mark down any answer lacking a unit so the habit is corrected early.
The candidate draws a ray diagram for a plane mirror or a converging lens with rays that do not obey reflection or refraction, or explains a shadow or an eclipse without using straight-line travel of light.
Ray diagrams are often copied from a book rather than constructed, so candidates do not internalise the rules that the angle of incidence equals the angle of reflection and that rays through the centre of a lens are undeviated. Straight-line propagation is assumed rather than stated.
What to do instead
Have candidates construct diagrams step by step with a ruler and protractor, measuring the angle of incidence before drawing the reflected ray. For shadows and eclipses, require the phrase 'light travels in straight lines' plus a simple sketch showing the blocked path.
The candidate states that the seasons are caused by the Earth being closer to the Sun in summer, or that day and night occur because the Earth moves around the Sun.
The distance explanation is intuitive and is reinforced by diagrams that exaggerate the elliptical orbit. The two rotations, daily spin and yearly orbit, are learned as separate facts and are not linked to the observations they explain.
What to do instead
Use a lamp and globe demonstration with a fixed tilt, showing that the same hemisphere receives more spread-out light in winter while the distance is nearly unchanged. Then have candidates write one sentence for day and night and one for seasons, naming the movement responsible in each.