Final answer:
The element that is intentionally changed in an experiment is the independent variable. It is manipulated to see its effect on the dependent variable while all other potential influencing variables are controlled.
Step-by-step explanation:
The element that is intentionally varied or changed in an experiment is known as the independent variable. This is the factor that the experimenter manipulates to determine if it causes any changes in the dependent variable, which is what is being measured in the experiment. All other variables that could influence the outcome must be controlled; these are called control variables. For example, in an experiment testing how fertilizer affects plant growth, the independent variable would be the presence or amount of fertilizer used, while the dependent variable would be the plant growth that is measured. Control variables might include factors like the amount of water or sunlight each plant receives.