CCNY – ENGL-217

Prof. Davidow

David A. A. Balaban – 23572639

Introduction

Science is never absolute. An equation, a theorem or even a law can be wrong and rewritten as long as someone can prove so. To do so, it’s necessary to come up with a way of portraying scientific information and experiments so that there can be accountability for it. That way, if the scientific method is followed it will be possible to re-create the conditions and results of certain experiments. That’s the lab report. A document whose format and guidelines have been created by the scientific community in an effort to streamline and reassure the effectiveness of scientific experiments.

Moreover, a lab report can be split in eight components: Title, Abstract, Materials and Methods, Results, Discussion, Conclusion, References, and Appendix. This essay will use those eight components to compare two different lab reports: “Temperature and pressure measurements of an ideal gas that is heated in a closed container” from Virginia Tech and “Perception of Different Sugars by Blowflies” written by Alexander Hamilton.

Report Components

Title

While both reports have a title, report 1’s is not too difficult to understand and it still portrays what is the experiment being performed technical manner. On the other hand, report 2’s title is incredibly simple and still portrays what the experiment is all about. Even though the titles were written differently they both fulfill its task of introducing what is the experiment the report is describing.

Abstract

Lab Report 2’s abstract is extremely well written, it describes what the experiment is and how it is performed without being technical. The abstract also mentions the author’s expectations for the results and if the results agree to them. Meanwhile, report 1 has an introduction that does give the reader an insight on the scientific theory being proved by the experiment. Nonetheless, report 1’s introduction does not explains the reasoning why to performing this experiment, nor does it gives any insight to who first performed it or discovered the observed relationship or experiment.

Materials and Methods

Lab Report 1 discusses the procedure for the experiment and it does so by clearly stating the next steps and how to perform them. It’s a clear and succinct explanation that is well fitted for a Lab Report.

Lab Report 2 on the other hand, clearly mentions the methods and materials used on the experiment, even giving out the concentration of the chemicals used. By doing so, the author makes it easy to replicate the conditions for the experiment to be performed again.

Results

Both Lab Reports display their results in an appropriate manner. While Lab Report 1 does so by discussing the raw data collected in this section, while it is displaying the collected data and its interpretation in an appendix, Lab Report 2 displays the raw data and doesn’t really discusses it, but just talks about all of the results for the experiment.

Discussion

The discussion for both Lab Reports is surprisingly similar, lab report 1’s discussion focuses on the comparison between the expected and the experimental results, and what that means for the experiment. Similarly, Lab Report 2’s discussion focuses on whether the experimental results agreed with the author’s initial hypothesis or not. Moreover, lab report 2’s discussion also acts as its conclusion.

Conclusion

For the conclusion, only lab report 1 have one. It concludes the experiment, by discussing if the results were appropriate or not, and what caused the error disparity if there were any. While Lab report 2 doesn’t explicitly have a conclusion it is appropriately concluded in its discussion.

References:

“Temperature and Pressure Measurements of an Ideal Gas That Is Heated in a Closed Container.” Sample Lab Report #2, www.writing.engr.psu.edu/workbooks/labreport2.html Accessed on 20th March of 2019

Lab Report 1:

Temperature and Pressure Measurements of an Ideal Gas That Is Heated in a Closed Container

Introduction

This report discusses an experiment to study the relationship of temperature and pressure of an ideal gas (air) that was heated in a closed container. Because the ideal gas was in a closed container, its volume remained constant. The objective of the experiment is to test whether the ideal equation of state holds. In the equation,

where p is the pressure the gas, V is the volume, m is the mass, R is a constant, and T is temperature. This report presents the procedures for the experiment, the experiment’s results, and an analysis of those results. 

Procedures

In this experiment, air (an ideal gas) was heated in a pressure vessel with a volume of 1 liter. Attached to this pressure vessel was a pressure transducer and thermocouple to measure the pressure and the temperature, respectively, of the air inside the vessel. Both of these transducers produced voltage signals (in Volts) that were calibrated to the pressure (kPa) and temperature (K) of the air (the atmospheric pressure for where the experiment occurred is assumed to be 13.6 psia). In addition, the theoretical temperature (K) of air was calculated as a function of the measured pressured values (kPa). 


Results and Discussion

This section analyses the results of the experiment. The experiment went as expected with no unusual events that would have introduced error. The voltages as measured for the pressure and temperature transducers appear in Table A-1 of the Appendix. Also included in the Appendix are the equations used for calibrating those voltages with the actual pressures and temperatures. These equations led to the values of pressure and temperature that are shown the third and fourth columns of Table A-1. From these values, a graph between temperature (K) and pressure (kPa) was created (Figure A-1). As can be seen from the graph, the relationship of temperature versus pressure is roughly linear.

As part of this experiment, the theoretical values of temperature were calculated for each measured pressure value. In this calculation, which used the ideal gas equation, the volume and mass were assumed to be constant. These theoretical values of temperature are shown in the final column of Table A-1. From this final column arose Figure A-2, a graph of ideal temperature (K) versus pressure (kPa). As shown in this graph, the relationship between temperature and pressure is exactly linear.

A comparison between the graph showing measured data (Figure A-1) and the graph showing theoretical data (Figure A-2) reveals differences. In general, the measured values of temperature are lower than the ideal values, and the measured values are not exactly linear. Several errors could explain the differences: precision errors in the pressure transducer and the thermocouple; bias errors in the calibration curve for the pressure transducer and the thermocouple; and imprecision in the atmospheric pressure assumed for the locale. The bias errors might arise from the large temperature range considered. Given that the temperature and pressure ranges are large, the calibration equations between the voltage signals and the actual temperatures and pressures might not be precise for that entire range. The last type of error mentioned, the error in the atmospheric error for the locale where the experiment occurred is a bias error that could be quite significant, depending on the difference in conditions between the time of the experiment and the time that the reference measurement was made. 


Conclusion

Overall, the experiment succeeded in showing that temperature and pressure for an ideal gas at constant volume and mass follow the relation of the ideal gas equation. Differences existed in the experimental graph of temperature versus and pressure and the theoretical curve of temperature versus pressure. These differences, however, can be accounted for by experimental error.

Appendix: Experimental Data and Plots 

This appendix presents the data, calculations, and graphs from the experiment to verify the ideal gas equation. The first two columns of Table A-1 show the measured voltages from the pressure transducer and the temperature transducer. Column three shows the measured values of pressures calculated from the following calibration curve for the pressure transducer:

where V equals the voltage output (volts) from pressure transducer, and p equals the absolute pressure (kPa). Column four presents the measured values of temperature (K) calculated from the calibration curve for the thermocouple:

where Tref equals the ice bath reference temperature (0°C), V equals the voltage (volts) measured across the thermocouple pair, and S equals the thermocouple constant, 42.4 µV/°C. Finally, column 5 presents the ideal values of temperature for the corresponding measured values of pressure. These ideal values arise from the ideal gas equation (PV=mrt). Figure A-1 shows the graph of temperature (K) versus pressure (kPa) for the measured case. Figure A-2 shows the graph of temperature versus pressure for the ideal case.

Figure A-1. Temperature versus pressure, as measured by the transducers.

Figure A-2. Temperature versus pressure, as calculated from the ideal gas equation.

Lab Report 2:

Perception of Different Sugars by Blowflies

by Alexander Hamilton

Biology 101 October 24, 2009

 Lab Partners: Sharon Flynn, Andi Alexander

ABSTRACT

 To feed on materials that are healthy for them, flies (order Diptera) use taste receptors on their tarsi to find sugars to ingest. We examined the ability of blowflies to taste monosaccharide and disaccharide sugars as well as saccharin. To do this, we attached flies to the ends of sticks and lowered their feet into solutions with different concentrations of these sugars. We counted a positive response when they lowered their proboscis to feed. The flies responded to sucrose at a lower concentration than they did of glucose, and they didn’t respond to saccharin at all. Our results show that they taste larger sugar molecules more readily than they do smaller ones. They didn’t feed on saccharin because the saccharin we use is actually the sodium salt of saccharin, and they reject salt solutions. Overall, our results show that flies are able to taste and choose foods

In this experiment we tested the ability of the blowfly Sarcophaga bullata to taste different sugars and a sugar substitute, saccharin. Because sucrose is so sweet to people, I expected the flies to taste lower concentrations of sucrose than they would of maltose and glucose, sugars that are less sweet to people. Because saccharin is also sweet tasting to people, I expected the flies to respond positively and feed on it as well.

METHODS

We stuck flies to popsickle sticks by pushing their wings into a sticky wax we rubbed on the sticks. Then we made a dilution series of glucose, maltose, and sucrose in one-half log molar steps (0.003M, 0.01M, 0.03M, 0.1M, 0.3M, and 1M) from the 1M concentrations of the sugars we were given. We tested the flies’ sensory perception by giving each fly the chance to feed from each sugar, starting with the lowest concentration and working up. We rinsed the flies between tests by swishing their feet in distilled water.

We counted a positive response whenever a fly lowered its proboscis. To ensure that positive responses were to sugars and not to water, we let them drink distilled water before each test. See the lab handout Taste Reception in Flies (Biology Department, 2000) for details.

RESULTS

Flies responded to high concentrations (1M) of sugar by lowering their probosces and feeding. The threshold concentration required to elicit a positive response from at least 50% of the flies was lowest for sucrose, while the threshold concentration was highest for glucose (Fig. 1). Hardly any flies responded to saccharin. Based on the results from all the lab groups together, there was a major difference in the response of flies to the sugars and to saccharin (Table 1). When all the sugars were considered together, this difference was significant (t = 10.46, df = 8, p < .05). Also, the response of two flies to saccharin was not statistically different from zero (t = 1.12, df = 8, n.s.).

DISCUSSION

The results supported my first hypothesis that sucrose would be the most easily detectable sugar by the flies. Flies show a selectivity of response to sugars based on molecular size and structure. Glucose, the smallest of the three sugars, is a monosaccharide. The threshold value of glucose was the highest in this experiment because a higher concentration of this small sugar was needed to elicit a positive response. Maltose and sucrose are both disaccharides but not with the same molecular weight or composition. It has been shown that flies respond better to alpha-glucosidase derivatives than to beta-glucosidase derivatives (Dethier 1975). Because sucrose is an alphaglucosidase derivative, it makes sense that the threshold value for sucrose occurs at a lower concentration than that for maltose. This might also be the reason why sucrose tastes so sweet to people. My other hypothesis was not supported, however, because the flies did not respond positively to saccharin. The sweetener people use is actually the sodium salt of saccharic acid (Budavari, 1989). Even though it tastes 300 to 500 times as sweet as sucrose to people (Budavari, 1989), flies taste the sodium and so reject saccharin as a salt. Two flies did respond positively to saccharin, but the response of only two flies is not significant, and the lab group that got the positive responses to saccharin may not have rinsed the flies off properly before the test. Flies taste food with specific cells on their tarsal hairs. Each hair has, in addition to a mechanoreceptor, five distinct cells – alcohol, oil, water, salt, and sugar – that determine its acceptance or rejection of the food (Dethier, 1975). The membranes located on the tarsi are the actual functional receptors since it is their depolarization that propagates the stimulus to the fly (Dethier, 1975). Of the five cells, stimulation of the water and sugar cells induce feeding, while stimulation of the salt, alcohol, and oil receptors inhibit feeding. More specifically, a fly will reject food if the substrate fails to stimulate the sugar or water receptors, stimulates a salt receptor, or causes a different message from normal (e.g., salt and sugar receptors stimulated concurrently) (Dethier 1963). Flies accept sugars and reject salts as well as unpalatable compounds like alkaloids (Dethier & Bowdan, 1989). This selectivity is a valuable asset to a fly because it helps the fly recognize potentially toxic substances as well as valuable nutrients (H. Cramer, personal communication). Substances such as alcohols and salts could dehydrate the fly and have other harmful effects on its homeostasis (Dethier, 1976). Thus, flies are well adapted to finding food for their own survival.

ACKNOWLEDGMENTS thank Prof. Cramer for help with the t-test and my lab partners for helping me conduct and understand this experiment.

LITERATURE CITED

Campbell, N.A., & J.B. Reece. 2008. Biology, 8th ed. Pearson Benjamin Cummings, San Francisco. Budavari, S., et al. 1989. The Merck Index. Merck & Co., Rahway, NJ. Biology Department. 2000. Taste Reception in Flies. Biology 101 Laboratory Manual, Hamilton College, Clinton, NY. Dethier, V.G. 1963. The Physiology of Insect Senses. Methuen & Co., London. Dethier, V.G. 1976. The Hungry Fly. Harvard University Press, Cambridge. Dethier, V.G., & E. Bowdan. 1989. The effect of alkaloids on sugar receptors and the feeding behaviour of the blowfly. Physiological Entomology 14:127-136.

Table 1. The average number of flies in each lab group that fed from 0.3M concentrations of each chemical tested. The mean + standard deviation is shown. chemical tested number of 10 flies responding glucose 3.2 + 1.5 maltose 7.8 + 2.3 sucrose 8.6 + 2.1 saccharin 0.2 + 0.5

Fig. 1. Taste response curves of flies to different concentrations of the sugars glucose, maltose, and sucrose.

Fig. 2. Chemical formulas of sucrose and maltose (Biology Department, 2000). Glucose is a monosaccharide and is shown as part of each of these molecules