Chemistry Practice

Method 1 Table:

[pic 1]

Method 2 Table and Graph:

[pic 2]

[pic 3]

First of all the formula for density is mass divided by volume. Thus the gradient of the graph can be seen as the density, as it fits the formula. So the density for the first volume (5cm^3) is 5.02/5, which is 1.004g/cm^3.[pic 4][pic 5]

Conclusion- Method two was logically the one with less error, as a burette was used which is a much more accurate instrument than a pipette. Due to the graph for method 2 and the visible measurements in the table, it can be noted that the volume of the water is directly proportional to the mass, as one rises so does the other, for example at 10cm^3 the mass is 10.01 g, and at 20cm^3 the mass is 20.07g, which is a significant increase, therefore concluding that the relationship between the two quantities is directly proportional. Also this can be expressed by the strong positive correlation in the graph. Also we know it is directly proportional as algebra states that a=b/c, so b=ac and c=b/a, so density= mass/volume, and thus mass=density*volume. The hypothesis was that the liquid was water as it was at room temperature, and the literature value of water is 1.010g/ml, and at 25^c the value is 0.997g/ml which is a very close and precise value to the one we get from the graph, 1.003380079g/ml. Therefore this gives us a difference of only 0.99%, which proves how accurate the numbers are.

Evaluation- The experiment was carried out quite well, and the results were reliable and accurate because of the graph’s literature value only being 0.99% different than the actual literature value of water. The graph showed a positive correlation and the experiment did not contain any errors, other than the ones which could have been caused by human error. The main errors which occurred were due mainly to procedural, which could be like misjudging of measurement or putting too much liquid, however these could be reduced by averaging out the samples, however no repeats were included. Consequently, one of the improvements next time would be to repeat the practical three times, thus leading to averaged and precise values. Also to improve accuracy a more calibrated beaker could be used, which gives more accurate readings, thus improving the chance of the literature value to be met with. However during the experiment no methodical error were made, which is why the data is believed to be accurate.  If the experiment was to be carried on, there would probably be a boiling test to make sure what the unknown liquid really was, and then measure the uncertainty difference between the two methods to clearly find out which one gives a more exact figure. However method one would not be to useful, as not many figures and statistics back it up.