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Lab Report Introduction This laboratory exercise was an investigation to determine the density of water through the usage of different glassware as basis for comparison in varying levels of accuracy and precision. As density is an intensive physical property, it is dependent on temperature hence requiring that the temperature of the water was first recorded before proceeding to measurements. With value of density being the purpose of the lab, water volume and mass were recorded with different instrumentation given that density is a ratio of mass per volume. The equipment used was first conditioned by rinsing with water. A 100ml beaker was used to collect water but was first weighed in order to later calculated the mass of water added. The experiment was structured in a way whereby water was aliquoted to the beaker using four different methods (graduated cylinder, serological pipet, volumetric pipet, and buret) in measurable increments of around 10ml, and weighed each time using a digital scale in grams. For each method, the addition of water and its weighing was repeated five times totaling 50ml of water. The data recorded allowed for calculations of corresponding values of volume and mass in each trial. This in turn is how value of density of water is obtained. Aforementioned, another aspect of the experiment is the comparison of precision and accuracy of laboratory equipment in the measurement of volume. This may be done by comparison of values of density calculated per equipment to predetermined assignments of water density according to temperature (in this case .997296 g/ml at 24.0C). Calculations Other sheet Post-Laboratory According to the data and percent error, the serological pipet was best and most accurate when measuring the volume of a liquid. This is due to the fact that it has the lowest percent error thereby indicating that it is closest to the true value. Instrument Density(g/mL) % Error Graduated Cylinder .9754 2.196 Serological Pipet 1.002 .4717 Volumetric Pipet .9888 .8592 Buret .9888 .8592 If in another experiment, the volume of water used for each entry was doubled, density would not be affected. In terms of the actuality of the lab, increasing the volume would consequently increase the amount of mass as well by the same proportion. In fact, density is an intensive property that remains independent of the amount of matter present in the substance. This is due to the mathematical fact that density is ultimately a ratio that relates volume and mass; being a ratio, it remains consistent regardless of the size of the sample. While theoretically, density is an intensive property that remains a consistent ratio, simple lab technique constrains acquisition of density value according to measurements of mass and volume. Thus, in a case where temperature of the system is manipulated, it can be understood that due to the addition of kinetic energy, volume of the substance expands. Mass, on the contrary, is not affected by the temperature of the system. Thus, the density calculated would be less than that of the actual value. The validity of using a 20mL pipet tip to measure out 10mL in place of using a designated 10mL pipet largely depends on the accuracy and incrementation with which the pipets are each marked. That being said, if the marking and accuracy of the pipets are the same, then the 10mL pipet may still be the better option. For the 10mL pipet tip, a challenge of precisely drawing up an accurate 10mL is the primary concern. A similar challenge of drawing up an accurate 20mL of water is true for the 20mL pipet. However, while the water drawn may be completely dispensed without concern for the 10mL pipet, using the 20mL pipet comes also with the necessity to be able to stop dispensing water at an accurate point. Thus, using a 20 mL pipet is in a sense, less valid. All instruments used for this investigation were fairly precise in that it consistently measured out similar amounts of water and followed particular proportions and ratios given by intensive properties of density. This is further supported by the fact that the r-squared value for three of the four graphs are actually equal to 1 hence suggesting a strong positive correlation between the mass and volume as expected. Thus, the instruments were precise for the fact of consistency between different entries. That being said, precision is not the same as accuracy; one can use precise instruments that yield consistent results between trials, but the instrument itself may actually be yielding a consistently wrong result that is far from accurate. Conclusion This experiment compares the usage of different apparatus (a graduated cylinder, serological pipet, volumetric pipet, and buret) in terms of its ability to accurately and precisely measure the volume of water. With each corresponding entry of volume, the mass of water collected as well. The primary goal of this investigation was to ultimately determine a calculated density using these measured values of volume and mass (given that density is a ratio of mass per volume); the calculated density was then compared to known values of density at the recorded temperature (in this case .997296 g/ml at 24.0C). According to data and calculations, the most accurate way to measure volume was by pipet which on average, had an error of only .4717% and density of .1.002g/mL While the densities as reported by the other instruments used was not entirely erroneous and out of range, attaining percent errors of only 2.196% and .8592%, the serological pipet was comparably more accurate. That being said, the usage of instrumentation in this lab was very precise as evaluated by the entries of each constituent part. Thus, the r-squared values for graduated cylinder, serological pipet, and volumetric pipet were all optimally equal to one with the buret being the only exception, but still equating .9998. R-squared is a value that statistically indicates how much of variation in dependent variables is accounted for by the independent variables. An r-squared value of one thus shows that all movements of a dependent variable are completely explained by the index. In other words, the volumes measured completely abide to and can be explained by the mass measured with a high level of consistency and precision for all apparatus. That the serological pipet was most accurately able to measure the volume is subject to various variables and perhaps errors that arose with usage of other apparatus. One of the largest issues that may have skewed volumetric accuracy in the graduated cylinder is the fact that residual water may have stuck to the sides of the container even after pouring. This is an issue that cannot be fixed. While this issue holds true for the other equipment as well, it applies only to a lesser degree. For the two pipets for example, the collection and release of water is subject to pressure change and induced vacuums. Thus, more of the water may be pushed out in comparison to the graduated cylinder. A large error with the volumetric pipet, which was perhaps actually best fit for measuring the volume of water, was observable during the experiment itself. The volumetric pipet used could not attain water and keep it at an amount that was consistent and accurate. The volume kept decreasing even though the pipet was not being manipulated. Thus, while there are indeed many other solutions, the issue was resolved by quickly transferring the water to the beaker after hitting the desired volume. The buret also saw errors that arose as well. One of the large issues with using a buret is the accumulation of measurement error as given by the way the instrument is designed. Buret measurement demands an accuracy reporting volume of both the initial and the ending. These are points at which issues of accuracy are posed. A final, though plausible, error applicable to all sections of the investigation is the usage of the digital scale. It is not probable that much error was induced by the scale, although this must be a factor that is considered. In any case, the measures of mass and volume from this experiment very well portray the density of water as per comparison with the known value of water density at the given temperature.