Scientific questions and observations

Light duration is the changed factor and average height is the measured outcome. In exams separate the cause variable from the effect variable.

Keeping the amount of salt and volume of water constant isolates the effect of temperature. Controlled variables are essential for a fair test.

Yellow colour can be seen directly while nutrient deficiency is a causal inference. An inference requires additional evidence.

The difference between final and initial readings gives the actual length. Recording only the final reading would be incorrect.

The direct answer is B: the solution was blue and its temperature was 32 °C. Qualitative data describe qualities in words, such as colour, texture, or appearance. Quantitative data give a measurable amount using a number and usually a unit. Option B contains both: “blue” is qualitative because it describes colour, and 32 °C is quantitative because it gives a temperature with a numerical value and unit. Option A is not the best record because “beautiful” and “pleasant” are personal judgments, not precise observations. Option C uses uncertain words such as “perhaps” and gives no measured values; “heavy” is vague unless mass is measured. Option D gives general judgments—“useful” and “safe”—without evidence or measurement, so it does not appropriately provide both data types. A strong observation separates what was directly noticed from personal opinion and records measurements clearly. Memory cue: descriptive word plus measured number and unit means qualitative plus quantitative data.

Conditions may differ at different times making comparison less reliable. Take repeated measurements at the same time.

Fertiliser and growth can be measured but the growth period is not specified. Adding a time period makes the question more precise.

When more than one factor changes it becomes difficult to identify the cause of the result. Keep other factors controlled.

Recording germinated seeds while omitting ungerminated seeds is selective data recording. It can make the germination percentage appear higher than it really is, leading to a biased conclusion. Accurate measurement means measuring all relevant outcomes correctly; here, some outcomes are not recorded at all. Exam tip: In an investigation, record both successful and unsuccessful results.

Increase in height over seven days can be measured clearly. An operational definition states how the outcome will be measured.

An unusual value may indicate either an error or a real variation. Check the procedure and repeat the measurement first.

The relationship between bending and light direction can be tested. A scientific question turns a direct observation into a measurable relationship.

The purpose of a scientific drawing is to show structure clearly. Neat lines and organised labels are necessary.

Light and darkness are clear conditions but seed type water and temperature must be kept the same. Only then will the comparison be fair.

Recording all values maintains transparency and allows the cause of variation to be checked. Data should not be hidden.

Senses provide qualitative information but instruments are needed for precise numbers. Additional investigation is needed to establish causes.

The question asks how container width affects the time required for water to evaporate. The factor being deliberately changed is container width, so it is the independent variable. The response to that change is the time taken for evaporation, which must be measured. This response is the dependent variable because its value may depend on the width of the container.

Option B is correct because the investigation records evaporation time as its outcome. To make the comparison fair, factors such as the amount of water, temperature, airflow, and starting conditions should be kept as similar as possible. Option A is the independent variable, not the measured result. Water colour and room decoration do not answer the scientific question and should not be treated as the outcome.

The group without fertiliser provides a baseline condition. This makes the effect of fertiliser easier to compare.

The word better does not specify a clear measurement. Replace it with a measurable outcome such as height leaf number or mass.

Smelling an unknown substance directly may be unsafe. Do not make such an observation without proper safety instructions.

Wilting may have several causes so lack of water is not a certain conclusion. Gather additional evidence before assigning a cause.

The comparison conditions duration and measurable outcome are clearly stated. These are features of a precise scientific question.

Different instruments may vary in accuracy and scale. Use the same checked instrument for comparison.

Good and poor do not provide clear measurements and may vary by observer. Use values such as height or leaf number.

Obtaining similar results when another person follows the same method demonstrates reproducibility. Record the method clearly.