NB G6 Science common mistakes
NB G6 Science · Understand the traps and how to avoid them.
When asked to identify the independent variable in a described experiment, the student names the outcome being measured (e.g., plant height) instead of the factor the experimenter deliberately changed (e.g., amount of light).
Students conflate 'what I change' with 'what I measure' because both feel like 'the variable' in everyday speech, and the described setup lists the measured result last, which draws attention.
What to do instead
Train a two-column routine: for every experiment, write 'I changed ___ on purpose' and 'I measured ___ as a result.' Only the first entry is the independent variable. Practise on five short scenarios until the routine is automatic.
The student writes a conclusion that goes beyond the data, claiming a general rule ('plants always need exactly 6 hours of light') from a single trial with one plant per condition.
School science rewards confident-sounding conclusions, and students imitate textbook phrasing without distinguishing a supported claim from an overgeneralisation.
What to do instead
Require conclusions to cite the specific numbers observed and to state a limit ('in this class trial, plants with more light grew taller'). Teach the phrase 'this evidence suggests' versus 'this proves', and ask for one improvement (repeat trials, more plants) in every conclusion.
When predicting what happens to a food web if one population is removed, the student assumes only the direct predator is affected and ignores indirect effects on other species.
Students reason along a single arrow in a food web diagram rather than tracing the whole network, and they treat arrows as 'who eats whom' without following the consequences of population change.
What to do instead
Practise 'trace the chain both ways' exercises: remove one organism, then list every population that gains or loses food, then predict each change. Use a three-step template: direct effect, effect on the predator's other prey, effect two links away.
The student labels a food chain's arrow as 'the predator eats the prey' and then misidentifies the direction of energy flow, or says energy is used up and does not return, but then claims matter also disappears.
Everyday phrasing ('the hawk eats the mouse') reverses the arrow convention, and students do not separate the one-way flow of energy from the cycling of matter.
What to do instead
Drill the rule 'the arrow points to the eater and shows where energy goes.' Then use a two-statement check for every ecosystem question: energy flows one way and is lost as heat; matter cycles and is reused. Have students label one example of each on a diagram.
When asked why a desert plant or a fish has a particular structure, the student describes the structure ('it has thick leaves') but never connects it to survival or reproduction in that environment.
Students memorise structure names separately from function, so a question asking 'why' gets a description instead of an explanation.
What to do instead
Enforce a sentence frame: 'This [structure] helps the organism [function] in its environment because [reason].' Practise with five organisms from different habitats until the causal link is always present.
The student classifies an unfamiliar organism by one visible trait (e.g., 'it lives in water, so it is a fish') instead of using a defined set of characteristics.
Single-feature classification is fast and matches everyday categories, and students do not know which features are reliable for grouping (body covering, how young are born, breathing organs).
What to do instead
Teach a decision sequence with at least three checkpoints (body covering, method of obtaining oxygen, how offspring develop) and require all three before naming a group. Include a counterexample such as a whale or dolphin to break the 'water means fish' shortcut.
The student treats a change in appearance (dissolving, melting, a balloon inflating) as proof that a new substance has formed, or treats a clear chemical change (rusting, burning) as merely physical.
Students judge by visibility rather than by whether a new substance with different properties is produced, and dissolving looks like disappearance.
What to do instead
Use a fixed test: can it be reversed by simple physical means, and is the material still the same substance? Practise sorting ten examples with the question 'is this the same substance in a new form or a new substance?' and require a reason for each.
The student explains a moving object's behaviour by saying 'the force keeps it moving' or 'the force runs out', rather than recognising that a net force changes motion and friction opposes motion.
Everyday experience of pushing a cart suggests motion requires continuous force, and the idea that an object continues moving without a force contradicts intuition.
What to do instead
Use the statement pair 'force changes motion; no net force means steady motion or rest.' Have students analyse a rolling ball with a force-arrow diagram showing the push ending while friction acts, and predict what happens on a smooth versus rough surface.
The student names the water cycle stages in order but cannot explain where the energy driving evaporation and the water vapour come from, or confuses evaporation with boiling.
The cycle is often learned as a labelled diagram to be recited, so the Sun as the energy source and the role of temperature are not linked to the stages.
What to do instead
Re-teach the cycle as an energy story: the Sun warms water, liquid water at the surface becomes vapour (not only at boiling), vapour cools and condenses. Ask 'where did the energy come from and where did the water go?' for each stage.
The student explains day and night or the seasons by saying Earth moves closer to and farther from the Sun, or by saying the Moon makes its own light.
Diagrams of elliptical orbits and bright-looking moons create a plausible but wrong mental model; the true cause (Earth's rotation, axial tilt, reflected sunlight) is less intuitive.
What to do instead
Use a physical model: a tilted globe and a lamp. Have students show that one rotation gives day and night while the tilt changes sunlight angle across the year. State explicitly that the Moon reflects sunlight, and check understanding with a 'what would happen if' prediction.
When asked whether a technology or human activity is beneficial, the student gives a one-sided answer ('it is good because it is convenient') without naming a cost, risk, or trade-off.
Students treat science-and-society questions as opinion prompts and do not know that a balanced claim requires both benefits and drawbacks supported by evidence.
What to do instead
Require a three-part answer: benefit, cost or risk, and a recommendation with a reason. Practise on familiar cases (plastic packaging, dams, wind turbines) using a two-column table before writing the answer.