Scientific questions and observations

This question tests a relationship between two measurable variables. Identify clear independent and dependent variables in exams.

Repeating the measurement under controlled conditions helps identify the cause of variation. Link repetition and standardisation with reliability.

A broad conclusion should not be drawn from a single sample. Identify generalisations based on limited evidence.

The yellow leaf is a direct observation while the cause is stated as a possibility. Separate facts from possible explanations.

The amount and particle size of the solute can affect dissolving time. Control other influential variables in exams.

Salt concentration and germination percentage can both be measured. Look for measurability in testable questions.

The direct answer is B: differences in instrument calibration may make the data inconsistent. Calibration means checking an instrument against a known standard so that its readings are trustworthy. If temperatures are recorded every five minutes with different thermometers, one thermometer may read slightly higher or lower than another even when the liquid has the same temperature. Then an apparent change may come from the instruments rather than the liquid. Option A is wrong because using different thermometers cannot make time stop. Option B is correct because calibration differences can create systematic differences and reduce comparability. Option C is wrong; a colour change is not certain and is unrelated to this measurement issue. Option D is too strong; temperature can still be measured, but the data may be less reliable. Best practice is to use the same suitable calibrated thermometer, keep its position and method constant, and record possible limitations.

Both initial and final heights are needed to determine actual growth. Relate change to the initial value in exams.

Recording only desired results is selective bias. Choose complete and objective data recording in exams.

The number of leaves is the measured outcome. Treat the variable recorded as the effect as the dependent variable.

An unusual value may result from error or a real event. It should not be discarded without investigation.

The word better is vague and must be converted into a measurable property. Give operational definitions to vague terms.

Strong smell can be a subjective qualitative observation. Identify limitations of sense-based observations.

Changing two variables together makes it difficult to isolate the cause. Change one independent variable at a time.

A repeated numerical measurement from a standard instrument is reproducible. Choose objective and repeatable data.

Soil type may affect growth and confuse the effect of fertiliser. Identify confounding variables in exams.

This question clearly specifies duration groups and a measurable outcome. Choose questions with focused conditions.

The direct answer is B, reducing error caused by the viewing angle. A liquid surface is usually curved at the edge; this curved surface is called the meniscus. If the eye is above or below it, the line of sight makes the level appear different. This is parallax error. Keeping the eye level with the meniscus makes the sight line nearly horizontal and gives a more accurate reading; for water, the bottom of the meniscus is normally read. Option A is wrong because eye position does not change liquid colour. Option B is correct. Option C is wrong because it does not enlarge the container. Option D is wrong because reading correctly cannot increase the liquid volume. Exam cue: eye level with meniscus means less parallax.

Initial and final measurements provide evidence of change. Strengthen descriptions with numerical data.

A control group provides a normal baseline for comparing effects. Link controls with comparison.

The direct answer is C. An objective observation uses a clear definition and something that can be counted or measured, so another person can check it. “Twelve fully developed leaves” gives a number and a defined condition: only leaves meeting the stated development criterion are counted. Option A, “looked good,” is a personal opinion and different observers may disagree. Option B, “about many leaves,” is vague, gives no exact number, and has no clear meaning. Option C is correct because it is specific, measurable, and repeatable. Option D, “seemed weak,” is also a subjective impression without a stated measurement. Reliable science replaces feelings with agreed criteria, counts, units, or recorded observations. Memory cue: objective means observable, countable, and checkable.

The amount of water becomes an additional influential variable. Keep all relevant conditions constant for a fair test.

Asking about magnitude or relationship produces richer data. Convert yes-or-no questions into measurable ones.

For a valid comparison, all measurements must be expressed in the same unit. For example, 2 cm = 20 mm, so 15 mm and 2 cm should first be converted into either millimetres or centimetres. Comparing only the numerical values can give a wrong conclusion because the units differ. Exam tip: make units uniform before comparing, adding, or finding an average.

A numerical value obtained with a standard instrument can be repeated by another person. Identify verifiable evidence.