Scientific questions and observations

Correct answer: B. Does the duration of light affect the average height of a plant

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

Correct answer: A. Amount of salt and volume of water

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

Correct answer: A. The leaf is yellow is an observation and the plant lacks nitrogen is an inference

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

Correct answer: A. Place the object at a clear mark and subtract the initial reading from the final reading

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

Correct answer: B. The solution was blue and its temperature was thirty two degrees Celsius

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.

Correct answer: A. Inconsistency in measurement

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

Correct answer: A. Does fertiliser affect plant growth

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

Correct answer: A. The cause of the result will become unclear

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

Correct answer: A. Selective data recording

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.

Correct answer: C. Does daily water amount affect the increase in plant height over seven days

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

Correct answer: B. Keep it recorded and repeat the measurement procedure

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

Correct answer: A. Several plants bend toward a window so the question asks how light direction affects bending

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

Correct answer: A. The scientific clarity of the drawing will decrease

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

Correct answer: A. Do seeds germinate at different rates in light and darkness

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

Correct answer: B. Record all values and check the procedure

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

Correct answer: B. Some qualities can be sensed but instruments are needed for precise measurement

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

Correct answer: B. Time taken for evaporation

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.

Correct answer: A. Comparing growth of fertilised plants with plants receiving no fertiliser

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

Correct answer: A. Does more water make a plant better

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

Correct answer: A. Violation of a safety rule

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

Correct answer: A. The leaves are wilted so the plant definitely lacks water

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

Correct answer: C. Will identical plants receiving eight hours and four hours of light differ in average height after seven days

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

Correct answer: A. Differences among instruments may make comparison less reliable

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

Correct answer: A. It is vague and subjective

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

Correct answer: A. Having another person repeat the same method

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