Chemical Laboratory Practice

Prelab Preparation

Before each lab, attend the lab lecture, where details of your next experiment will be discussed. Come to lab lecture and the laboratory prepared, having already read through the experiment description in the Lab Manual. Plan your experiment ahead of time so that you make efficient use of your time in the lab. After the first experiment, each lab will have a set of prelab questions. Answer these questions on the sheet in your Lab Manual. Your answers will be collected by your laboratory teaching assistant before you can do the experiment.

Many experiments will be done with a lab partner. Be sure you and your partner have agreed to work together and are well prepared.

Laboratory Procedures and Notebook

You will need a bound "Composition Book", available from the bookstore, in which to record your lab data. This composition book should be used only for ChemLab data and calculations. The pages should be tightly bound. Spiral notebooks are NOT satisfactory.

The purpose of your lab notebook is to provide an accurate, permanent record of experimental work. It should be sufficiently detailed so that the experiment could be reproduced by referring only to the notebook and references listed in the notebook. Leave the first three pages of your lab notebook blank for a table of contents and notebook summary.

For each experiment, your notebook should contain the following:

1. Purpose: One or two sentences describing the goal of the experiment.

2. Procedure: A description of how the experiment was done. Normally this will come from the experiment description, and a simple reference to that source is sufficient (you do not have to copy down the procedure into your notebook). However, any changes from the cited procedure should be noted here.

3. Experimental: Record all data (weights, volumes, etc.) and observations (color changes, etc.) directly into the notebook. Record what you actually did, not what you intended to do. All data should be entered directly into the notebook, not transferred from scraps of paper.

4. Calculations: Any calculations that you need to do during the lab period should be shown in the notebook. Always bring a calculator to lab.

5. Conclusions: One or two sentences stating the principal result(s) of the experiment.

6. Your lab partner's name, if applicable.

At the end of each lab period, your TA must sign your lab notebook! The lab report you hand in for each experiment must contain a xerographic copy of the lab notebook page having your TA's signature. You are responsible for obtaining a signature from your TA copying the page for your lab report.

Lab Reports

After completing the lab, it is standard scientific practice to write a lab report that summarizes your findings. The lab report should be written in grammatically correct English in whole sentences. This report must be an individual effort. Lab partners have to write their own reports, in their own words. Lab reports that are too similar to one another will not be accepted and both reports will receive zero credit.

A lab report will usually contains the following sections:

1. Introduction: Write a sentence or two to inform the reader of the purpose and nature of the experiment.

2. Experimental Procedure: This section is a description of how the experiment was done. Normally this will come from the experiment description, and a simple reference to this source is sufficient (you do not have to copy down the procedure into your report). However, any changes from the cited procedure should be noted here, and any procedure you design must be described in sufficient detail that another student could repeat your experiments.

3. Data and Observations: This portion of the lab report consists of all quantitative measurements (data) and any qualitative observations recorded during the course of the experiment. Presentation of this information in a tabular format or in a chart or graph is preferred, as experimental results are then easily comprehended. Charts or graphs should be generated on a computer. Hand drawn charts and graphs are not acceptable. We expect to find the data and observations both in your lab notebook, and in the lab report.

4. Calculations: Calculations are any results that you obtain from your data by applying mathematical operations to your data. For example, initial and final buret readings are data, but the volume of liquid actually delivered from a buret is a calculation. (This is because the volume of solution used is found by subtracting the initial buret volume from the final buret volume.) You should clearly show how your calculations were done by actually substituting the numbers in your formulas. If your calculations are repetitive, show a sample calculation in detail and only the results for similar ones. As with the experimental data and observations, presentation of calculations in a table is also recommended. If appropriate, quantitatively estimate your experimental error.

5. Discussion: You should answer any questions in the experiment description in this section of the lab report. The overall significance of your results, an explanation of your results, and any major sources of error should be discussed here.

6. Conclusions: Write one or two sentences stating the principal result(s) of the experiment.

7. Lab notebook sheet. A copy of your signed lab notebook page must be included.

8. Your lab partner's name, if applicable.

Lab reports are due at the beginning of your next lab period. Reports that are up to one week late will be penalized 25%. No lab reports will be accepted more than one week late.

GRADING

The Laboratory segment of Chemistry 131 contributes a maximum of 250 points toward your final grade. The ten components, seven laboratory experiments and three Excel projects, will be graded on a basis of 25 points each. Laboratory reports will be graded on the basis of the requirements listed immediately before this GRADING section. It is important to note that Experiment 6 is the only one where the accuracy of your results can affect your grade. You should always report what you observe, independent of what your expectations may be. There are a variety of reasons for your experimental results to vary from anticipated or "text book" results.

Grading is NOT an exact science and, if you believe you deserve more credit, return your graded lab report to either a Lab TA or to Dr. Hickey. Before doing so, write a note on the front of your report that clearly explains why you think more credit is due.

ACADEMIC HONESTY

In the lab, academic honesty means the objective reporting of your own observations and the writing of your laboratory report by yourself. When you make use of someone else's data the source of the data must be stated in your report. Any material taken from another source, including procedures given in the lab manual, must be acknowledged as such. Each lab report must be your own. Using another laboratory report as a guide, even if you change the wording, is plagiarism, and is a violation of academic honesty. I repeat:

Your lab report must be an individual effort. Lab partners have to write their own reports, in their own words. Lab reports that are too similar to one another will not be accepted and both reports will receive zero credit.

labpractice02.htm, August 25, 2006