osmosis variables

hey can anyone help me by answering the following question: ( i am doing the osmosis experiment on potato cells in different molarities of sugar solution to see how the mass of the chip changes)...

list the other factors which you will keep THE SAME to make it a fair test, and the effect these variables would have if they are NOT kep constant

thankyou

ive come up with a few like temperature etc but cannot explian what they may do to not make it fair!