Sulphuric Acid Experiment

The results do not support the hypothesis that a higher surface area to volume ratio would result in sulphuric acid being diffused into the agar cubes in the shortest amount of time. This is evident in the results as the exact opposite to what was predicted occurred. Instead of the smallest cube with the largest surface area to volume ratio of 1cm3 having the quickest diffusion rate, it conversely took the longest at 0.092 cm3 per second, whilst the 2cm3 cube with 0.0384 cm3 per second took the least amount of time. This directly refutes the hypothesis. There was also no consistent trend evident in the results. Between the two largest blocks of 2cm3 and 3cm3, there was only a 0.00243 cm3 per second, however, and in contrast to the hypothesis,

The temperature of the sulphuric acid was not measured throughout the experiment, however the room in which the experiment was conducted was kept constant, so the chance of any large error due to unknown temperature of the sulphuric acid was most likely reduced. The amount of sulphuric acid used was also controlled by measuring 100mL with a 100mL measuring cylinder to ensure that the results would be consistent. The volume of the agar cubes was calculated from the surface area of each agar cube, both before and after they had been in the sulphuric acid. This increased the reliability of the results as it allowed the rate of diffusion of the sulphuric acid into the agar cubes to be calculated more accurately. The concentration of the acid was 0.1M, which was placed in all three agar cubes to maintain consistency of results. Another variable of the experiment that was controlled was the time in which the agar cubes spent in the sulphuric acid. The time allowed calculation of the rate of diffusion. The size of the agar cubes was controlled by using a grid and scalpel to, as accurately as possible, cut the agar cubes into the appropriate sizes. The shape of the agar cubes was also controlled. In future, this could be experimented with to investigate how different shaped agar blocks affect surface area to volume ratio and hence the rate of

A larger sample size could have enabled averages to be resulted, and the experiment could have had several trials until concordant results are attained to increase the reliability. To enhance the accuracy of the results, a machine such as a cheese wire to cut straight along the edge could have been employed that would more accurately cut the cubes and hence reducing human error. This would be efficient as there is a large chance of human error when cutting the cubes by hand as the agar is slippery. Cubes with different sizes could be observed to improve the validity of the experiment. The weight of the bottom of the cubes pushing against the beaker likely caused an error to occur. This could have impact different sized cubes to varying extents. Human error also occurred when the 3cm3 cube had to be repeated as it was initially incorrectly measured. This could have contributed to the results being less reliable as the concentration of phenolphthalein in the agar cube could have been different from that of the other cubes (Unknown, 2008). The method was quite successful and produced relatively accurate results. Next time, a substance such as hydrochloric acid could be used instead of sulphuric