Variables
1 Independant Variable: An independent variable is a factor that can be varied or manipulated in an experiment (e.g. Time, temperature, concentration.) It is drawn on the x-axis. It is usually what will affect the dependent variable. An Independent variable will answer the question "What do I change?" In my experiment, the independent variable will be the concentration of sucrose solution. I intend to use equally spread out concentrations of 0M, 0.1M, 0.2M, 0.3M and 0.4M (Molars) as, if range too narrow/wide it would not be representative. The extent and range of the concentration must always be recorded on the x-axis.
2 Dependant Variable: A dependent variable is what you measure in the experiment and what is affected during the experiment, drawn on the y-axis. It responds to the results of the independent variable. In this case, the dependant variable is mass of the potato, which will depend on the concentration of the sucrose solution. The change in mass of the potato cylinders is measured on % to make the comparisons valid, as all cylinders will have differing initial masses. Also, weigh to 2 decimal places for accuracy as two different values could be recorded as the same if recorded to one decimal place. (ie to one decimal place two results would show 1. 5.0grams
2. 5.0grams but to 2 decimal places the same results would be 1. 5.01 2. 5.08.)
3 Controlled Variables: A controlled variable is something in an experiment that doesn't change between tests. This enhances the tests validity and fairness. In order to make it a fair test we have controlled variables e.g. length and size as different surface area affects rate of osmosis. Also, the volume of sucrose solution (10cm3) will stay the same, the length and diameter of the cork bearer and the temperature. Also, use boiling tubes so the potato cylinders don’t get stuck. Repeat the testing of each concentration five times as it will make it easier to identify anomalous results so we can...