Variables in an experiment

The direct answer is B, the independent variable. The independent variable is the factor deliberately changed by the experimenter. Here the student uses holes of different sizes, so hole size is the chosen input. The time taken for water to flow is the measured response and would be the dependent variable. Step by step: select hole size; keep other conditions such as water volume and container comparable; measure flow time; compare times; therefore hole size is independent. A is wrong because dependent variable is the measured effect, not the changed hole size. B is correct because size is deliberately varied. C is wrong because a controlled variable is kept the same, whereas hole size is not the same. D is wrong because “result” describes an outcome such as flow time, not the factor being changed. The question asks for the role of hole size, so classify the input rather than the measurement. Exam cue: “different sizes,” “different temperatures,” or “different concentrations” often identify the independent variable.

The water flow time is the measured result so it is the dependent variable. In exams identify the time outcome.

Keeping the initial water level the same ensures that only hole size is tested. In exams treat it as a controlled variable.

The amount of detergent is changed so it is the independent variable. In exams identify the deliberately changed amount.

Foam height is measured as the result of changing detergent amount. In exams choose the outcome variable.

The shaking time is kept the same so it is a controlled variable. In exams keep additional influential factors constant.

The compression distance of the spring is changed so it is the independent variable. In exams identify the changed quantity.

The car's speed is measured as the result of spring compression so it is the dependent variable. In exams identify the measured effect.

The car's mass can affect speed so it should be kept the same. In exams treat it as a controlled variable.

The heating time is deliberately changed so it is the independent variable. In exams identify the changed duration.

Food temperature is measured as the result of heating time. In exams a measured temperature is the dependent variable.

The amount of food is kept the same so it is a controlled variable. In exams identify factors kept constant.

Spoon size is deliberately changed so it is the independent variable. In exams identify the factor changed by the experimenter.

The direct answer is C: dependent variable. In the spoon experiment, the time taken for sugar to dissolve is an outcome that is measured after changing or comparing another condition, such as stirring, spoon type, or water temperature. Because it responds to the experimental condition and is recorded, it is dependent. A would be the factor deliberately changed. B would be a condition kept the same, such as the amount of sugar or water when appropriate. D, a constant, is any quantity that remains unchanged and is not the measured result. Thus the dissolving time belongs to C. The question asks “what is the time,” so look for the measured outcome. Memory cue: what you measure is usually dependent.

Water volume is kept the same so it is a controlled variable. In exams keep it constant for a fair comparison.

In an investigation, the independent variable is the feature deliberately changed by the investigator. The dependent variable is the response measured afterward. Controlled variables are kept the same so that the comparison is fair. Separating these roles helps identify what was changed and what effect was observed.

Here, surfaces of different colours are placed in sunlight, so surface colour is deliberately changed. It is therefore the independent variable, making option A correct. The temperature is measured as the response, so it is the dependent variable. Factors such as the material, size, thickness, time in sunlight, and light conditions should be kept as similar as possible. Colour is not a constant because it is the feature being varied.

Temperature is measured as the effect of surface colour so it is the dependent variable. In exams choose the measured quantity.

Surface size is kept the same so it is a controlled variable. In exams keep other conditions constant.

The amount of sand is deliberately changed so it is the independent variable. In exams identify the changed amount of material.

Filtration time is measured as the result of sand amount so it is the dependent variable. In exams choose the time outcome.

The same water volume ensures a fair comparison. In exams identify it as a controlled variable.

The hanging load is changed so it is the independent variable. In exams identify the cause changed by the experimenter.

The direct answer is D: dependent variable. Spring extension is the amount by which the spring length increases, usually measured after a load is applied or changed. The load is the cause or independent variable, while the extension is the response. Therefore the measured extension is dependent on the load. A would be the deliberately changed load, not the resulting length. B would be something kept fixed, such as the same spring. C means a quantity that remains unchanged, whereas extension is expected to change. The reasoning is: apply or vary load, observe and measure the increase in length; the observed effect is dependent. Memory cue: cause is independent, measured spring response is dependent.

Using the same spring is a controlled condition so only load is tested. In exams identify apparatus kept constant.

The number of batteries is deliberately changed so it is the independent variable. In exams identify the changed electrical factor.