Variables in an experiment

Direct answer: Option D is correct. In an experiment, the independent variable is deliberately changed, the dependent variable is measured as the result, and controlled variables are kept the same. In the cloth-drying experiment, drying time is the quantity measured after the drying conditions are arranged. Reasoning: a condition is varied; the cloth responds; the time taken to become dry is recorded. Because it is the outcome that depends on the experimental condition, it is the dependent variable. Option A is wrong because an independent variable is the factor changed by the investigator, not the recorded time. Option B is wrong because a controlled variable remains constant, such as cloth type or water amount. Option C is wrong because an observation is the act or record of noticing a result; the variable itself here is the measured time. Option D works because drying time is the measured outcome. Memory cue: changed = independent, measured result = dependent, kept same = controlled.

Keeping the cloth size the same allows a fair test of fan speed. In exams treat it as a controlled variable.

The direct answer is B: independent variable. The independent variable is the factor that the investigator deliberately changes to study its effect. The dependent variable is what is measured in response. In this investigation, the student uses different temperatures and measures the time taken by ice to melt. Step by step: identify what is changed—temperature; identify what is measured—melting time; the changed factor is therefore the independent variable. Option A is wrong because melting time is the dependent variable: it changes in response to temperature and is measured. Option B is correct because temperature is deliberately varied by the student. Option C is wrong because a controlled variable is kept the same, such as the ice mass, container, or room conditions where possible. Option D is wrong because a constant is a quantity intentionally held unchanged, not the factor varied across trials. The experiment is strongest when only temperature changes and other relevant conditions remain the same. Memory cue: independent means “I change it”; dependent means “data depend on it.”

Melting time changes due to temperature and is measured. In exams identify it as the dependent variable.

Different-sized cubes may melt in different times so their size should be kept the same. In exams understand the role of controlled variables.

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

The number of flowers is the measured result so it is the dependent variable. In exams identify the counted outcome.

Keeping the soil type the same allows a fair comparison of sunlight effects. In exams treat it as a controlled variable.

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

The amount of stain removed is the measured result so it is the dependent variable. In exams identify the outcome.

Water temperature may also affect stain removal so it should be kept the same. In exams control additional influential factors.

The independent variable is the factor changed by the experimenter for testing. In exams choose the cause variable.

The dependent variable is measured as the effect or result of the experiment. In exams identify the effect variable.

Keeping controlled variables constant allows only the independent variable's effect to be observed. In exams identify the fair-test condition.

The experimenter changes the distance so it is the independent variable. In exams identify the changed spatial factor.

The number of nails attracted changes with distance and is counted. In exams identify the measured result.

Keeping the magnet type the same ensures that only the effect of distance is tested. In exams treat it as a controlled variable.

The amount of water is deliberately changed so it is the independent variable. In exams identify the experimenter's change.

The sprouting time is measured and depends on the amount of water. In exams treat it as the dependent variable.

Temperature is a factor kept the same so it is a controlled variable. In exams identify factors kept constant.

Uncontrolled factors may also affect the result making the cause unclear. In exams keep all necessary conditions constant.

Pendulum length is changed so it is the independent variable. In exams identify the deliberately changed length.

The answer is B, dependent variable. In an experiment, the independent variable is what the investigator deliberately changes, while the dependent variable is the result measured after that change. In a pendulum investigation, the time for one oscillation is obtained by observing and measuring the motion, so it is an outcome and therefore dependent. A, independent variable, would be something deliberately varied, such as length, mass, or release condition. B is correct because time is measured. C, controlled variable, means a factor kept the same, such as the pendulum material or release angle when appropriate. D, constant, is a general word for something unchanged and does not identify the measured outcome. A useful check is: ‘What did I measure?’ The answer is usually the dependent variable.

The bob mass is kept the same so it is a controlled variable. In exams identify properties kept constant.

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