A control variable is a factor in an experiment that is kept constant to ensure that the results are due to the independent variable. By maintaining these variables, researchers can isolate the effects of the independent variable on the dependent variable, leading to more reliable conclusions. For example, in a study examining the effect of temperature on plant growth, factors like light and water should be controlled. Control variables are essential in scientific research because they help eliminate alternative explanations for the observed outcomes. If a control variable changes, it could influence the results, making it difficult to determine the true relationship between the independent and dependent variables. Properly identifying and managing control variables enhances the validity of the experiment.