Why Do Potato Prisms Decline

The results provide evidence that when there was an increase in the sodium chloride concentration the mass of the potato prisms declined. At the zero percent concentration there was an increase of mass by 1.75%, from there the 1%, 3%, 5% and 10% begun on a downward trend with the percentage change in mass declining. The graph was on a steady decline from 0% being the highest point with a change of mass of 1.75% finishing with the 10% solution on a decline of -12.28%. From observing the scatter plot the data points were not far from the line of best fit, indicating the results were hardly affected by random errors. Resulting in fairly precise and reliable results.

The hypothesis stated ‘As the concentration of sodium chloride increases the mass of the potato in the solution will decrease.’ This was supported as with the increase of sodium chloride concentration the change in mass was on a steady decline with each percentage of sodium chloride losing greater amounts of mass. The 0% was the only solution to have an increase of mass where as the other percentages steadily declined with the increase of concentration.
The controlled variables need to be kept constant as they strongly influence the results of the experiment.
They need to be kept the same throughout the practical in order to test the relationship between the dependent and independent variables. If they are not kept constant the results will be unreliable as each test performed will use a different mass of potato, the time spent in the solution will be inconsistent and the amount of solution in the beaker would vary. Keeping the variables constant is an important factor as the concentration of the sodium chloride solution should be the only factor influencing the percentage change in mass when comparing the different samples
tested.

Potential random errors that could have occurred include the removing of the potatoes from the solution at exactly 10 minutes. This is an error as if they are not removed at the same time there would be varying results as some potato cubes would have spent more or less time in the sodium chloride solution. The starting of the timer is also a potential error as if the timer is not started when the potato prisms hit the solution the exact time spent in the solution is unknown. The shape and mass of the potato must be identical in order to produce reliable results. If the test is conducted with a variety of masses and shapes the outcome would be unreliable as there would be variations in surface area and weight. This results in the potatoes undergoing osmosis with other factors contributing to its occurrence as the surface area and weight are not being kept constant.

A systematic error that could potentially occur is the electronic scale giving incorrect mass measurements. This would result in all of the data being off, either too high or too low. The stop watch could also cause potential systematic errors as it could be a poorly calibrated instrument that is two fast or two slow, resulting in all the times being off.

Possible improvements include increasing the sample size as it would improve the experiment with reliability and accuracy. With an increased sample size an average can be calculated resulting in more precise and reliable results, as with a larger sample size there is a decrease in potential random errors. By increasing the sample size in this experiment there is the ability to obtain a range of masses for each concentration, that can then be averaged out to find a more reliable final mass which is then calculated into a percentage. Another improvement could involve an alternative way to cut and prepare the potatoes in order to produce 5 exact potato prisms. This could be performed by using a cutter that already has the outline of the desired shape. By applying this it would improve the accuracy and precision of the experiment as it would produce 5 prisms that are exact and have the same surface area.