Think about the lab procedure you just read. label each factor below v if it was variable during the procedure or c if it was constant.
molecule size (large starch molecules vs. small glucose molecules)
material used as the membrane
amount of substances used
number of trials
whether the molecules diffused through the membrane (tubing)

In the experiment given the variables are the first and last items listed, whereas the controls are all three of the middle items listed.

When creating an experiment to test a hypothesis, we can identify three kinds of variables

The dependent variable is what we are trying to measure, it is the entire reason for performing the experiment. In this case, the dependent variable is whether or not molecules diffused through the membrane (tubing).  

The Independent variable is one that will not change in reaction to the others. In this example, it is the molecule size, given that the size of a molecule does not depend on other factors and will not change in reaction to them.

The control variables are the material used as the membrane, the number of substances used and the number of trials performed, given that they all remain constant for each of the cases studied.

Therefore, items one and five are variables, one is independent while item 5 is the dependent variable, and the three middle items listed are the controls, given that they will remain constant through the entire experiment.

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The factors which remained constant are as follows -

The factors which have shown variation are as follows -

Explanation

Some factors with in the experiments remained constant from the point of starting of the experiment to its end. While some factors were varied to study its impact on the experiment rate of progression or on the final product formed. Thus , out of the following given factors, the ones that remained constant are -

The factors which have shown variation are as follows -

it is a learned trait

explanation: