Tokushima Public High School Entrance Examination - Science common mistakes
Tokushima Public High School Entrance Examination - Science · Understand the traps and how to avoid them.
When a problem gives a circuit with two resistors and asks for current or voltage, the candidate plugs all numbers into one formula (e.g., V = IR) without first deciding whether the resistors are in series or parallel, and computes a single combined value.
In class, Ohm's law is often drilled as a single formula, and candidates memorise 'V = IR' without internalising that the same current flows through series elements while the same voltage appears across parallel branches. Under time pressure they pattern-match to the formula they practised most.
What to do instead
Before any calculation, redraw the circuit and label each junction; mark series segments (one path, shared current) and parallel segments (branch points, shared voltage). Write the equivalent resistance step by step (series: R = R1 + R2; parallel: 1/R = 1/R1 + 1/R2), then apply V = IR to the whole circuit and again to each element. Practise 10 mixed circuits and state the series/parallel judgement in writing each time.
On questions about forces and motion, the candidate treats 'force is applied' as equivalent to 'object moves in the direction of the force', and concludes that a ball thrown upward has zero acceleration at the top or that a constant push guarantees constant speed.
Everyday experience (pushing a heavy box that barely moves) reinforces a naive 'force = motion' intuition, and Japanese junior-high textbooks introduce inertia and action-reaction together, so candidates blur them. The top-of-flight case is a classic trap they have not resolved conceptually.
What to do instead
Learn three separate statements and test each problem against them: (1) no net force means constant velocity (which may be zero), (2) net force causes acceleration, not velocity, (3) action-reaction forces act on different objects and never cancel. For projectile problems, draw the velocity arrow at the top (horizontal, nonzero) and the acceleration arrow (downward, g) separately.
In wave and sound/light questions, the candidate confuses frequency, wavelength, and amplitude, writing that a louder sound has a higher frequency or that changing amplitude changes the speed of the wave.
The three quantities are introduced together and all are drawn on the same waveform diagram, so the labels blur. Candidates also over-generalise 'bigger wave = faster wave'.
What to do instead
Anchor each quantity to one measurable feature: amplitude = height of the wave (loudness/brightness), frequency = number of oscillations per second (pitch/colour), wavelength = distance between crests. Memorise v = f × λ and note that in a fixed medium v is constant, so f and λ trade off. Redraw and label one waveform per practice question.
When asked to write a chemical equation, the candidate writes correct formulas but leaves the equation unbalanced, or balances by changing subscripts (e.g., writing H2O2 for water) instead of adding coefficients.
Balancing is taught as a separate drill, and under exam pressure candidates treat the equation as a formula-recall task. Changing subscripts feels like the quickest way to make atom counts match.
What to do instead
Adopt a fixed routine: write formulas from valences, list each element's atom count on both sides in a table, then adjust only coefficients, re-checking after each change. Finish by counting every element once more. Practise 15 equations including combustion of hydrocarbons and neutralisation, where H and O counts are easy to get wrong.
On questions distinguishing physical and chemical changes, or identifying a substance from its properties, the candidate labels any visible change (melting, dissolving, bubbling) as a chemical change, or assumes a gas being produced always means a chemical reaction.
Textbook examples (burning, rusting) are vivid, but the boundary cases (dissolving sugar, boiling water, carbon dioxide escaping from soda) are less practised, and 'bubbles' is over-associated with reaction.
What to do instead
Use one criterion: a chemical change produces a new substance with different properties, and is generally not easily reversed. Build a two-column list of 15 everyday changes and justify each with that criterion, explicitly including dissolving, melting, and gas evolution from heating.
In ion and precipitation questions, the candidate predicts whether a precipitate forms by guessing from the names of the two solutions rather than checking solubility, and writes ionic charges without balancing them (e.g., AgCl2).
Solubility rules are memorised as a list rather than applied, and ionic formula writing competes for working memory with the reaction prediction, so charge balance is skipped.
What to do instead
Memorise a short solubility table (nitrates and most chlorides soluble; AgCl, PbCl2, BaSO4, CaCO3, Ag2CO3 insoluble) and apply a two-step check: identify the ions present, then test each possible pairing against the table. When writing a formula, write the charges above each symbol and cross-multiply, then verify the total charge is zero.
In genetics and cell-division questions, the candidate states that a child's traits come equally from both parents, or that a recessive trait cannot appear if one parent shows the dominant trait, and confuses mitosis with meiosis when explaining gamete formation.
Junior-high genetics is taught through Mendelian ratios without a firm link to chromosome behaviour in meiosis, and the terms 'dominant' and 'recessive' are misread as 'strong' and 'weak'.
What to do instead
Draw the allele pairs explicitly: parent genotypes (AA, Aa, aa), then a Punnett square for each cross, and read the phenotype ratio off the square. Separately, list mitosis (body cells, chromosome number unchanged, two identical cells) versus meiosis (gametes, chromosome number halved, four cells). Do five crosses including Aa × Aa and Aa × aa.
When interpreting experiments on photosynthesis or respiration, the candidate concludes that a plant only photosynthesises in light and only respires in darkness, or reads a gas-exchange graph as showing no respiration during the day.
Textbook diagrams separate the two processes into different chapters, and the net gas exchange measured in experiments hides the fact that respiration runs continuously.
What to do instead
State the rule explicitly: respiration occurs continuously in all living cells, day and night; photosynthesis occurs only in light in cells with chloroplasts. For any gas-exchange graph, identify the compensation point where uptake equals release and explain both curves as the sum of the two processes. Practise explaining why a plant in bright light still releases some CO2 at night.
On Earth-science questions about earthquakes and volcanoes, the candidate reads the P-wave/S-wave arrival-time graph as giving distance directly from the time axis, or claims that S-waves travel through the outer core because they are 'stronger'.
The travel-time graph requires subtracting two arrival times, which is a two-step operation candidates collapse into one. The S-wave shadow zone is taught as a fact without the reasoning that S-waves cannot pass through liquid.
What to do instead
Practise the graph procedure aloud: read the S-wave arrival time, read the P-wave arrival time, subtract to get the time difference, then read the distance from the difference axis. For interior structure, memorise the evidence chain: S-wave shadow zone implies a liquid outer core; P-wave refraction implies a solid inner core.
In weather and astronomy questions, the candidate explains seasonal temperature differences by saying Earth is closer to the Sun in summer, or describes a warm front passing as bringing short, heavy showers followed by cold, dry air.
The distance explanation is intuitive and reinforced by diagrams that exaggerate Earth's orbital eccentricity, while front types are memorised as labels without their associated weather sequences.
What to do instead
Fix the cause of seasons as the tilt of Earth's axis changing the Sun's altitude and day length, and note that Earth is actually closest to the Sun in early January. Build a two-row table for warm and cold fronts: warm front = slow approach, long steady rain, then warmer air; cold front = brief heavy rain, then colder, clearer air. Test each against a weather map symbol.