Well, you may have errors in measuring the concentration of your solution, or in weighing the potato slices before and after the experiment. If you use different potatoes, or different parts of the potato are different (eg one part for some reason dryer) then that could add to the error. If you put a potato into an isotonic solution it should remain the same weight, but if you have more solute in the water than in the potato, water from the potato will be drawn out (like salting a snail or tomato), but if the water has less solute than the potato, it will be drawn into the potato, making it heavier.
In the experiment it includes several separate tests and errors that can be easily occurring. One of the errors is the potato cores were not necessarily all the same weight to even begin with. However, another source of error is the cores were not exactly completley covered by the solution, which is due to the larger beaker.
An independent variable is the variable you think is the cause,while a dependent variable is the effect. you manipulate the independent variable and measure the outcome in the dependent variable.
