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Monroe Township High School

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Natural Science

Writing in the Field of Natural Science

This section of your manual will be devoted to the scientific laboratory report. It is intended to provide a guide for the writing of a formal laboratory report in any of the science classes that are offered in Monroe Township High School. There is no standard way of writing these reports and many colleges and professors have their own standards when it comes to presenting data. This guide will enable you to correctly present data in this high school and also provide you with a basic method that can be applied to all situations in science.



Here are some frequently asked questions about lab reports that you might be interested in :

Why am I writing these reports?

These reports are written basically for documentation of results. Research scientists explore unknown scientific territory and record the journey in their notebooks. If the results of the journey add to the body of knowledge already present, other scientists will want to travel there also. The scientific report should ensure that others can reach the same conclusions with the same methods and materials. This is a validation of the processes used by the researcher and it must be accurate. One must obtain reproducible results.

What can I share with my lab partner?

Even though you and your lab partner performed the experiment together, you should each record the results in your own lab notebooks. You will each write a separate lab report based on these results. Each of you is responsible for a complete report and you should always work in the lab with this in mind. Your partner's name will appear on your lab report to alert the instructor that there will be another written documentation of the same experiment.

Since this is science, do I need to write properly?

You are being trained in science and part of this training involves written communication of ideas and results. The professional appearance of the report, the proper punctuation, grammar and writing style are just as important as the units and calculations. Take the time to proofread your work. Have someone else look for mistakes that you may have missed. Writing properly takes time and hard work. It is a direct reflection of your higher cognitive skills. More and more technical positions require sharp communication skills along with technical knowledge.

I know my results are terrible; will I lose points on my report grade?

Part of the lab report should deal with this problem. It is the experimenter's job to explain what went wrong and how this can be avoided if the procedure was performed again. Accidents do occur and must be documented. Bad results may occur because of accidents or a poor procedure. All results must be reported and then explained. If this is done properly, there will be no penalty.


Monroe Township High School Science Department
Laboratory Report Format

Title Page

The title page provides the following information :

1. Name of the lab experiment
2. Names of the lab partners
3. The date(s) the experiment was performed
4. The name of the instructor

The title page should be a separate page devoted only to this information.

Abstract (optional, check with instructor)

The abstract is the report in miniature. It summarizes the whole report in one, concise paragraph of about 100-200 words. The abstract does not summarize the experiment, it summarizes the report itself. Hence you cannot write the abstract until after you've completed the report.

The best strategy to use before you write an abstract is to summarize each section of the report in one sentence. Then try to organize this information into a short paragraph. The abstract should be a precise and specific summary.

Introduction (Purpose)

The introduction presents the subject of the report and acquaints the reader with the experiment. The following items are usually contained in the introduction :

1. A statement of the problem to be solved in the experiment.
2. Any background theory, previous research or formulas the reader might need to understand and perform the experiment.
3. The significance of the experiment.

Methods and Materials (Equipment)

This section can consist of a list. Be complete, accurate, and precise.

Experimental Procedure

This section states what you really did and what actually happened, not what the textbook said or what was supposed to happen. List all the steps in the correct order.

Results

The most important part of this section is the introduction or labeling of numerical results. Each block of information should be verbally introduced and provided with a clear and accurate verbal label. Even though numbers will be provided with units, each set of numbers must be labeled by the author so that the reader knows all about these results ahead of time.

It is also important to provide a sample calculation using one complete set of data. Once again, you must verbally introduce and label each step of the calculation to the reader.

Discussion

Your discussion is the single most important part of your report. In it, you will show your reader that you understand the experiment and can interpret it. Analyze and explain your results, focusing in on questions like these:

1. What results were expected? What results were obtained? If there were any discrepancies, how can you account for them?
2. Do any of your results have particular technical interest?
3. How do your results relate to your experimental objective(s)?
4. How do your results compare to those obtained in similar investigations?
5. What are the strengths and limitations of your experimental design?
6. If you encountered difficulties during the experiment, what were their sources? How might they be avoided in the future?

Conclusion

The body of your report should end with a brief concluding statement which summarizes the significant results of your experiment. In the plainest terms, your conclusion should answer the question, "So what?" Does your experiment confirm or contradict an established principle or theory?

Note: The results, discussion, and conclusion sections can be combined in various ways. Use whatever combination is most appropriate for your situation.

Appendices

Appendices may include raw data, calculations, graphs and other quantitative materials that were part of the experiment, but not reported in any of the above sections. Refer to each appendix at the appropriate point in your report.


Sample Lab Report


Predicting the Mass of Product in a Chemical Reaction










Title Page










Edward W. Keegan
Al Kaseltzer
25 December, 1997
Mr. Forman


Notes: The author of the report is listed first. The title of the lab is accurate and precise.



Introduction

The purpose of this experiment was to verify that chemical stoichiometry is a reliable mathematical method for predicting the mass of zinc chloride produced when 10.000g of zinc metal reacts with excess hydrochloric acid.

Notes : The experiment is a verification of a law of nature. It will not prove anything. The Law of Conservation of Mass has been proven already!
            The reader has been introduced to the chemical reaction and the amount of material being used.
            It also seems apparent that the mass of the product will be compared to an amount predicted by a known method.

Materials

1. Quadruple beam balance
2. Low form evaporating dish
3. 3M Hydrochloric acid
4. Zinc powder
5. 20 x 150mm pyrex test tube
6. water bath

Notes: Only the important materials are listed. Details that are common knowledge in the field such as mass boats, beakers and scoopulas are not listed. If the reader wanted to repeat your experiment exactly, this is what would be needed. The type of test tube and evaporating dish are very important to the experiment.

Experimental Procedure

1. 10.000g of zinc powder is placed in a test tube which was then placed in a cool water bath.
2. 20.0mL of acid was then added to the test tube slowly.
3. The reaction was allowed to proceed until no visible sign of a reaction was noticed. (stopped bubbling and no zinc was visible)
4. The contents of the test tube were then emptied into a pre-massed evaporating dish.
5. The contents of the dish were dried to constant mass. A white solid was left in the dish.
6. The evaporating dish and solid contents were then massed.

Notes: Only the important points of the procedure are included here. Phrases like "get the zinc" and "my partner poured the acid in" are never used. Obvious steps like "we massed out the zinc" are not included also.

Results

Chemical equation for the reaction used : Zn(s) + 2HCl(aq) ----> ZnCl2(s) + H2(g)

Calculation of predicted amount of product :

- 10.000g Zn x 1mole/65.38g = .1530moles Zn reacted
- Ratio of reactant to product is 1to1; therefore, .1530moles of Zn reacted will yield .1530moles of ZnCl2.
- .1530moles of ZnCl2 x 136.28g/mole = 20.85g
- Predicted amount of product(theoretical yield) = 20.85g
- Actual amount of product recovered in the experiment = 20.113g

Experimental Error Calculation :

Formula: [(Theoretical yield - Experimental yield)] x 100

Theoretical yield

Experimental error = 3.535% or 96.46% of the predicted amount was recovered in the lab.

See Appendix A: Raw data chart.

Notes: Each part of this section is introduced or labeled. The numbers have units and the reader is lead through the calculations in a logical progression. The author has not chosen to discuss the results in this section, so there will be a discussion section to follow. It is very important to show the reader what you did with the numbers in a neat and organized manner.

The author also refers the reader to his raw data chart located in the appendix if there are any questions about the numerical data.

Discussion

By using stoichiometry, the predicted amount of product was greater than the actual amount that was recovered in the lab. The error produced was small however, and there may be a few reasons why the error exists. One source of error maybe the presence of impurities in the zinc powder. This would lead to an over-estimation of product because it was assumed that the original amount of zinc powder would all react. The impurities may not have reacted leaving less than the expected amount of zinc to react.

Another area where this error may occur is during the drying process. Particles of solid may "pop" out during the process which would lead to less solid being massed. A watch glass may limit the amount of this error along with a slow drying process.

The final source of error may be with the reaction itself. Two things can be brought up here:

1. Even though there were no signs that the reaction was still taking place, one can never be sure that it was not unless the reaction is left for many hours. It may be wise to leave the reaction for 24 hours to insure completion.

2. The theoretical yield is the maximum amount of product that we can hope to obtain. In the real world, this is unlikely to happen. Some of the limiting reactant may be consumed in competing reactions. For this and other reasons, the actual yield in a reaction is ordinarily less than the theoretical yield (Masterson 83). In this case, zinc was the limiting reactant and may have gotten involved in side reactions which would lower the amount of solid left in the evaporating dish.

Notes: Even though some professors may allow the use of personal pronouns in a lab report, it is a good idea to avoid them. The use of "we" was unavoidable because it was part of a citation from a chemistry book. Avoiding the use of personal pronouns also requires that you plan out your sentences, and this is to your advantage.

This discussion contains everything that a good discussion should. The results are not written again, but analyzed. This section points out the significance of the results and identifies areas where error may have occurred. It also has a reference to a text which helps to explain the error.

Notice that there are no references to human error or faulty equipment. There is a suggestion on how to improve the procedure also.

Conclusion

For the reaction of zinc metal and hydrochloric acid, stoichiometry is a reliable method of predicting the mass of solid zinc chloride that will be produced. The experiment does show however that the predicted amount may be slightly higher than the actual yield, but this is consistent with the literature on the subject.

Notes: The conclusion has answered the purpose and has explained what learning has gone on. Stoichiometry will give a higher prediction than you will actually get, and that you may expect this to occur whenever you use this method.

References

Masterson, William L. Chemical Principles. 6th ed. Philadephia:
Saunders College Publishing, 1985.