Writing A Laboratory ReportLab reports often vary with field of study, as well as the teacher. In this course,

there are three basic report styles that may be used, depending on the nature of the experiment. No matter what report style is used, it is important to remember that each individual is responsible for writing down the data, especially if working in groups. If the other member(s) of your group are not present on the day the calculations are done, and have the only record of the data, the lab is still due on the announced day. Also, data should be recorded in a table, and not on scrap paper so that the necessary data is not accidentally lost or misused.

1. Informal

An informal report is the simplest to complete. This report is simply the completed lab worksheet, with all questions answered and blanks filled with the data from your experiment.

2. Formal

A formal report is a comprehensive report about the experiment. Such a report should include the following sections: Title, Purpose, Apparatus, Procedure, Data, Calculations, Conclusion, Error Analysis, and References. Each section should be completed as shown in the example that follows this section. Formal reports should be word processed if possible, but may be typed or neatly printed. Passive voice should be used in scientific reports, unlike reports in other fields of study. The use of passive voice is much like a newspaper reporter; the verbiage simply reports what happened in the experiment. Passive voice is third person, past tense, with no human subjects. I, we, you, they, he, or she should never appear in the report. For example, the directions say "Pour 400 mL of water into a beaker." Here is how this would be reported in passive voice:

400 mL of water was poured into a beaker.

Not: I poured 400 mL of water into a beaker. (human subject present) Pour 400 mL of water into a beaker. (command form; understood "you")

Do not instruct the person how to do the lab, but rather report exactly, in as much detail, what happened. Be sure to include observations such as color, size, odor, temperature, and general appearance.

Title - give a title to the experiment, not necessarily the same one as the lab manual

Purpose - tell why the experiment was done. Example: "The purpose of the experiment was to determine the color of various compounds when placed in a flame." (must be a complete sentence)

Apparatus - a list of any lab equipment and chemicals actually used to complete the experiment (not necessarily the same as the list in the lab manual)

Procedure - a play-by-play description of what happened during the experiment. Include the steps, data, and observations in your own words. Be sure to give plenty of specific details, especially on observations. Cleaning steps may be left out of the report. Don't forget to use passive voice and complete sentences! This should be in paragraph form... don't use step numbers. You may wish to include pictures or diagrams.

Data - a table or list of any numbers obtained from the experiment; also pictures of all your data readings is optional, but a good idea!

Calculations - show all calculations that were completed to obtain the answer to the experiment. You need only provide calculations for one trial if the experiment was repeated.

Conclusion - the final answer to the experiment. The conclusion should be a restatement of the purpose, but with the answer now included.

Error Analysis - provide an explanation of how you answer may not be exactly correct. If applicable, provide a % error calculation. Provide reasons for error in the experiment in addition to human error (i.e. flaws with the experiment, not your goof-ups!) Be sure to indicate whether the error will increase or decrease your answer.

experimental - theoretical% error = ----------------------------------------------- X 100

theoretical

The experimental value is the answer to the experiment that you determined by doing the procedure and the calculations. The theoretical value is what the answer should have been, in theory. This is sometimes called the "known" or "accepted" value. The accepted value for most experiments can be found in the CRC Handbook of Chemistry and Physics. Accepted values for stoichiometric experiments can be found by doing a stoichiometry problem, beginning with the amount(s) of reactant(s) used.

References - list any books that may have been used to provide information used in your report, such as accepted values. Use a typical bibliography entry. Format is not critical here, but be sure to provide enough information that a person could look up the information if needed.

A sample lab report is shown on the following page. Be sure to observe the format of the report, including spacing, underlining, and general form.

Neil RappAP Chemistry Period 1September 1, 2001

DENSITY OF WATER

Purpose: The purpose of the experiment was to determine the density of water.

Apparatus: Graduated cylinder, electronic balance, 250 mL beaker, dropper, water

Procedure: First, some distilled water was obtained in a 250 mL beaker. The water was clear in appearance, and had no odor. The mass of the empty graduated cylinder was determined to be 48.8400 grams. Then, the water was poured into the graduated cylinder. As the water level approached 50 mL, a dropper was used to add the water until exactly 50.00 mL of water was present in the cylinder. The cylinder was then placed on the balance again. The mass of the cylinder including the water was 98.6700 grams.

Data:

mass of dry graduated cylinder 48.8400 g

mass of grad. cylinder with water 98.6700 g

volume of water 50.00 mL

Volume of water

Mass of dry graduated cylinder

Mass of graduated cylinder with water

Calculations:

Mass of water: 98.6700 g - 48.8400 g = 49.8300 gVolume of water: 50.00 mLDensity = mass / volume = 49.8300 g / 50.00 mL = 0.9966 g/mL

% error = ((.9966 g/mL - 1.00 g/mL) / 1.00 g/mL) X 100 = 0.34% error

Conclusion: The density of water at room temperature was determined to be 0.9966 g/mL.

Error Analysis: There was a +0.34 % error in the density determination. Many possible errors could contribute to this error besides human error. The temperature of the cylinder itself may not have matched the temperature of the water. This would make the volume measurement slightly higher, which would result in a lower density. The precision of the measurements was limited by the volume, since fewer measured digits could be obtained using a graduated cylinder than the analytical balance for mass. In addition, human error was found to be present. Some contaminants from the countertop accidentally stuck to the metal after it was massed, but before it was submerged. This would result in a lower measured mass, which would also contribute to a lower density.

References: Accepted value for density of waterCRC Handbook of Chemistry and Physics, 63rd Edition. Page D-43.

3. Research Notebook

A third method of reporting is the research notebook. The notebook is an on-going log of steps and observations as they happen. This style of notebook requires the use of many measures that eliminate the chances of tampering of the contained information. Such security measures are taken, as a research notebook often contains instructions for make a new compound, which may be subjected to patent law, and eventually sale to an interested manufacturer. First of all, a cloth bound notebook must be used. The binding can not be glued, perforated, or hole-punched. This is so that pages may not be removed from the notebook, lest the entire book fall apart. Second, the notebook should be kept in ink. Any mistakes in the notebook must be crossed out with a single line, so that the writing can still be seen. Any blank area in the book that extends across all four columns and down more than 1/4 the page must be crossed out with a single "X". The date and time of the starting and ending step of each lab session's work should be recorded in the margin next to the corresponding step.

Aside from the security measures listed above, the notebook should contain basic information needed in any book. The first page should be a centered cover page that includes the name of the researcher, the course name, the school year, and title of the book. The second page (left hand side) should be blank. The right side should contain the table of contents, listing each lab experiment as they are completed with a title and page number. All subsequent pages must be numbered and divided into 4 columns, 2 on the left page and 2 on the right page. The title of the experiment should be listed at the top of the first page of that particular experiment. The titles of the 4 columns should appear on each page. The titles are: Procedure, Observation, Conclusion, and Equation. As the lab is performed, the procedure should be briefly described in the procedure, step-by-step. Each individual step should be numbered. If there is an observation from that step, it should be recorded in the observation column on the same line. After the lab is completed, conclusion and equations should be added. On the first line of the Equation column, a list of the ions that are believed to be present should be listed with their corresponding charge. Conclusions should be made and recorded as needed; most lines will not have a conclusion. Equations should be added to the notebook by simply copying them out of the textbook, but placing them on the corresponding line in the procedure. Any confirmation of an ion requires both a conclusion and an equation. A sample first page of an experiment is shown on the next page.

Sample Research Style Notebook

left page right page

Group I Known

Procedure Observation Conclusion

1

Equation

1/1/01 1. Obtained6:35 Group 1 am Known

1. Clear liquid, odorless

1. Group I ions are present

Hg22+, Pb2+, Ag+

2. Added 10 drops 6M HCl

2. White solid formed

2. Chlorides precipitated

Hg22+ + 2 Cl-

Hg2Cl2

Pb2+ + 2 Cl- PbCl2

Ag+ + Cl- AgCl

3. Added 5 drops HNO3

4. Added 10 drops hot water

4. Lead ions extracted

5. 4 drops 1M K2CrO4

added to hot water extract

5. Yellow ppt formed

5. Pb+2 is present Pb+2 + CrO4 -2 PbCrO4 (s)

It is imperative that you keep the procedure and observation section as you go, and not copy it later, lest your lab partner be absent the following day. Common procedures may be abbreviated, such as centrifugation, extraction, etc.The lab should continue on as many pages as necessary. Each experiment should begin on a fresh page.