Scientific questions and observations

A thermometer may need time to stabilise at the liquid temperature. Record the value after the reading becomes steady.

Selecting only tall plants makes the sample unrepresentative of the whole group. The selection rule should be unbiased.

The word better has no clear measurement method. Define the outcome using a value such as height number or time.

Repeated measurements can improve reliability for that plant but general conclusions remain limited. Use an adequate sample.

Data with dates and regular intervals reveal trends over time. Include units in the table as well.

Option A is correct because one trial is not enough to support a universal claim such as “always.” The result may be influenced by factors such as the amount of water, sugar particle size, stirring rate, or measurement error. Temperature can be measured with a thermometer and can be the independent variable in an experiment, so B and D are incorrect. Exam tip: Before making a general conclusion, repeat a controlled experiment and compare the average results.

While changing surface area the water volume and temperature should remain constant. This isolates the effect of surface area.

A colour chart provides a common reference and reduces observer variation. Standard categories are useful for qualitative data.

Sunlight and height may vary together but other factors such as water and soil may also act. A controlled investigation is needed to establish causation.

Changing the salt amount may also affect dissolving time. This makes the true effect of temperature unclear.

The direct answer is A: recording a plant height as only 25 is the most serious problem. A number is quantitative data, so its unit tells us what the number measures. Step by step: first identify the observation as height; next write the numerical value; then add a unit such as centimetres or metres. “25 cm” and “25 m” describe very different plants, while “25” alone is unclear and cannot be compared reliably. Option A is correct because the missing unit changes the meaning of the measurement. Option B, “green,” is a descriptive colour word and does not normally need a measurement unit. Option C, “rough,” describes texture, so a unit is not required for this observation. Option D, “fragrant,” describes smell and likewise is a qualitative observation, not a numerical measurement. Do not guess the unit after recording: write the value and unit together. Memory cue: number plus unit makes a measurement meaningful.

Forming a conclusion first is preconception and choosing supportive data is selective bias. Draw conclusions after considering all data.

Seasonal change occurs over months so regular long term records are needed. Keep dates and the observation method consistent.

Direct answer: Option A, after measuring the same quantity several times. Repeated measurements of one quantity may differ slightly because of random variation or measurement limits. The arithmetic mean is found by adding all readings and dividing by the number of readings: \(\text{average}=\frac{\text{sum of readings}}{\text{number of readings}}\). It gives a representative central value, although original readings must also be kept. Option A is correct because several comparable measurements can be combined meaningfully. Option B is wrong because one colour description is qualitative and offers no set of numerical readings for an average. Option C is wrong because one personal opinion is not repeated measurement of a measurable quantity. Option D is wrong because one value without a unit is incomplete and cannot be interpreted reliably. Exam cue: repeat, record, then average with units.

The direct answer is A. A fair comparison changes or compares the intended factor while keeping measurement conditions as similar as possible. Using the same instrument reduces instrument differences, measuring at the same time reduces effects of daily timing, and repeating measurements over several days reduces the effect of one unusual day. Option A therefore gives the strongest reliability. Option B mixes instruments and times, so differences may come from equipment or timing rather than the groups. Option C measures only one group and only once, so there is no proper comparison or repetition. Option D depends on memory, which is easily inaccurate and cannot be checked precisely. Good experiments use a consistent procedure, careful records, and repeated measurements. Exam cue: same method, same conditions, repeated trials.

Bird numbers can be counted under natural conditions. Keep the observation method consistent across time and location.

A question directs the investigation and a hypothesis is a testable statement about a possible result. Both are linked to evidence.

Without a unit the correct meaning of a numerical value is unknown. Include a unit in every quantitative column.

Without a clear procedure another person cannot repeat the investigation in the same way. Record steps instruments and conditions.

Observation creates curiosity and a scientific question shapes the investigation. Both are connected stages of scientific inquiry.

Actual growth is found from the difference between initial and final height. Always record a baseline value for comparison.

A scientific question tests a measurable cause-and-effect relationship. In exams identify questions that can be investigated.

A direct observation is information obtained by measuring or seeing something during the investigation. In this situation, the temperature was recorded at regular intervals, so a statement that reports the measured change is directly supported by the observations. Option C states that the temperature increased from fifty degrees to sixty-two degrees in six minutes. This is a record of measurement, not a prediction or an explanation.

Option A predicts that the liquid will boil, so it is an inference about the future. Option B proposes an unseen explanation involving invisible energy, which was not directly measured in the description. Option D makes a vague claim about the liquid’s nature rather than reporting a recorded result. Therefore C is the correct choice because it uses numerical temperature readings collected during the experiment.

The change in shadow length can be seen or measured so it is an observation. Stating its cause is an inference.

Beauty depends on personal preference and cannot be tested objectively. A scientific question should be measurable.