Tottori Prefectural Public High School Entrance Examination - Science common mistakes
Tottori Prefectural Public High School Entrance Examination - Science · Understand the traps and how to avoid them.
Writing a chemical equation with correct formulas but leaving it unbalanced, or balancing by altering subscripts (e.g., writing H2O2 → H2O + O2 as H2O2 → H2O + O instead of 2H2O2 → 2H2O + O2).
Candidates memorize the skeleton of familiar reactions and rush to fill in products; they treat balancing as a cosmetic step and reach for a subscript change because it is faster than adding coefficients.
What to do instead
Adopt a fixed routine: write formulas, then count each element on both sides in a small table, then adjust only coefficients, then recount. Finish by checking that the atom count matches for every element and that charges balance if ions are involved.
Confusing the direction of induced current with the direction of the magnetic field or the force on the wire, so that a question about a conductor moving in a magnetic field is answered with the field direction.
The right-hand and left-hand rules look similar on paper, and candidates learn them as a single 'hand rule' without separating the three quantities (field, current, force/motion).
What to do instead
Draw the three arrows (B, I, F) explicitly on the diagram before choosing a rule, and state which rule applies to which situation: force on a current-carrying wire versus current induced by motion. Practise by reversing one quantity at a time and predicting the result.
Treating 'work done' and 'energy' as interchangeable and claiming that an object moving at constant speed on a frictionless surface has increasing mechanical energy, or that no work is done whenever a force acts.
Everyday language uses 'energy' loosely, and candidates conflate the presence of a force with the transfer of energy, ignoring the displacement component along the force.
What to do instead
Apply the definition explicitly: work = force × displacement in the direction of the force. For each problem, list the forces, mark which have a displacement component, and track kinetic and potential energy separately before summing. Check that total mechanical energy is conserved only when no non-conservative work is done.
Describing the image formed by a convex lens or concave mirror by guessing from the object's position without applying the ray diagram, and mixing up real and virtual images.
The image rules are numerous and similar in wording, so candidates rely on a vague memory of 'bigger/smaller' rather than constructing the standard rays.
What to do instead
For every optics question, sketch the principal rays (parallel ray through the focus, ray through the centre, focal ray) and read off position, size, orientation, and whether the rays actually converge. Learn the boundary cases (object at 2f, at f) as anchors and compare each new case to them.
Explaining a chemical change by naming the product only, without identifying the ion or electron transfer, e.g., saying 'the precipitate forms because the solutions were mixed' or 'it neutralizes because it is an acid and a base'.
Candidates memorize observations (colour, precipitate, gas) as ends in themselves and never link them to the underlying particles, which the exam expects at the ionic level.
What to do instead
For each reaction, write the ionic equation and circle the ions that actually combine or the electrons that transfer. Practise converting every observation into a statement about specific ions (e.g., Ag+ and Cl- forming AgCl), and state which ions remain unchanged as spectator ions.
Mixing up mitosis and meiosis when explaining gamete formation or growth, claiming that meiosis produces identical cells or that mitosis halves the chromosome number.
Both are described as 'cell division', and the chromosome-number outcomes are easy to reverse under time pressure; candidates also skip the distinction between somatic and germ cells.
What to do instead
Build a two-column comparison covering purpose, number of divisions, chromosome number in daughter cells, and genetic variation, and anchor it to concrete examples (root tip growth versus pollen/egg formation). Before answering, ask 'is this about growth or about making gametes?'
Treating dominant and recessive alleles as 'strong' and 'weak' traits, and predicting offspring ratios without setting up the parental genotypes (e.g., assuming a dominant phenotype means homozygous).
Everyday meanings of 'dominant' mislead, and candidates jump to a 3:1 ratio without checking whether the parents are homozygous or heterozygous.
What to do instead
Always write the parental genotypes first (AA, Aa, or aa), then draw the Punnett square, then read the ratio. Explicitly note that a dominant phenotype can be AA or Aa and that a test cross is needed to distinguish them.
Reading a geological cross-section by treating the lowest layer as oldest in every case, ignoring folding, faulting, and intrusion that overturn the simple superposition rule.
The superposition principle is taught first and is memorable, so candidates apply it mechanically to diagrams that are designed to test cross-cutting relationships.
What to do instead
For each cross-section, first identify whether any layer is cut by a fault or intruded by magma, then apply the rule that a cutting feature is younger than what it cuts. Order events (deposition, folding, intrusion, erosion, faulting) in a numbered sequence before answering.
Answering weather questions by equating low pressure with 'bad weather' and high pressure with 'good weather' without linking to air movement, fronts, or the seasonal pressure pattern over Japan.
The shorthand is repeated in everyday forecasts, and candidates do not connect pressure systems to the direction of air flow and cloud formation, nor to the winter/summer pressure arrangement around Japan.
What to do instead
For each weather question, state the air movement (converging and rising at lows, diverging and sinking at highs), the resulting cloud and precipitation, and the season-specific pressure pattern (e.g., winter high over Siberia and low over the Aleutians). Draw the isobars and wind arrows.
Describing the Moon's phases or eclipses by the Moon's position relative to the Earth alone, forgetting that the observer on Earth sees a different illuminated fraction depending on the Sun-Earth-Moon angle.
Diagrams in textbooks show the Moon from above, while the question asks what an observer on the ground sees; candidates do not translate between the two viewpoints.
What to do instead
For every phase question, draw the Sun-Earth-Moon geometry from above, mark the half of the Moon lit by the Sun, then determine how much of that lit half faces Earth. Keep a separate note that a solar eclipse requires new Moon and a lunar eclipse full Moon, and that neither happens every month because of the orbital tilt.