Chemistry Laboratory

Laboratory notebook and reports

You must turn in some combination of laboratory notebook pages (originals) and a formal report.

Lab Notebook Format

Title and date –

Procedure - Reference procedure using correct MLA or APA format. Note any changes you are instructed to make in the procedure.

Safety and/or Waste Treatment - List the any additional safety precautions or special waste handling procedures called for in the experiment; these are usually given in the lab manual.

Data & Observations

This section will be written as you perform the experiment; the data you collect and observations that you make are recorded here. Perhaps the easiest way to collect your data and observations is to paraphrase the procedure as you go through the steps and then enter your observation and data for that step. Simply enter a one- or two-line statement to describe the operation and immediately afterwards, record your data. You do not need to write complete, grammatically correct sentences in this section as it is understood that you will be concentrating on the experiment. Here is a brief example:

Step 1 1.0042 g of NH₄Cl added to 5 mL of DI H₂O in medium-size test tube

obtained clear solution

test tube was cold to touch (endothermic process?)

Step 2 approx. 1 mL of AgNO₃ (aq) added dropwise to test tube

immediate formation of ppt

ppt was white, cloudy no heat observed no bubbles

Write all observations and data for the experiment in this section. This section is your rough draft for the report. As you record your data and observations, this section may become messy and unorganized which is to be expected. You may want to add a summary of your data in the form of tables, charts or lists to facilitate writing the report rather than trying to "hunt" through disjointed recordings.

Suggestion: Carefully read the experiment, more than once, and create a mental list of the type(s) of information you will be collecting. Plan in advance; if you need a data table, decide on the number of columns in the table and column titles and consider how much room on a page you need for your table(s) (or charts, lists). The post-lab write up cannot include any information which is not supported by the Data & Observation section.

Other Notebook Information

Provide at least two pages at the front of the notebook for a table of contents.

Always use non-erasable black or blue ink.

The top of each page should have your initials, the date and Expt #

Always record data directly into notebook; do not use scratch paper

Record colors, phases, odors and texture of all substances you observe.

Turn in the original pages (not the carbon copies) with your reports, even if the entire page is a deletion.

Do not remove any pages from your notebook except for those pages that are turned in with the reports.

To correct writing mistakes: draw a single line through the words or sentences you want to correct and place your initials after the deletion. To delete paragraphs, place a single X over the entire paragraph and initial the deletion. You may want to look at your deletions at some later date, this way, your original entries will be readable. Never use white-out or try to black-out your writing mistakes!

Sign and date the bottom of each page containing data before you leave for the day. (For half completed pages sign under the last data recorded so that you may use the remainder of the page for the next lab period.)

Have instructor initial all pages on which you have recorded data before leaving lab for the day.

Formal Report

A general guide for writing lab reports follows. Guidelines specific to each experiment may be found on the instructor web site.

Title Page

Include experiment name, date, your name, instructor name, and section number

Objective

A brief description of the purpose of the experiment. That is, why are you doing this experiment? To understand a concept? To determine a constant? To characterize a sample?

The objective (or goal) can usually be stated in one sentence or at most, a short paragraph. The objective is not always conveniently given at the beginning of each experiment in the lab manual. Often, the experiments in the manual begin with some background information which helps to elucidate the theoretical aspects of the experiment and it is left to the student to deduce the purpose of the experiment. Occasionally, the goal is stated in the body of this background text. Therefore, it is crucial that the student read each experiment thoroughly before coming to lab so that an appropriate (and accurate) objective can be formulated. This will also prepare the student for the experiment itself.

Introduction

The Introduction should explain the theory behind the experiment and explain how the procedure used will accomplish the objective of the experiment. This section will not be lengthy but it should be sufficient to allow the reader can understand the logic of the experiment simply by reading this section.

The introduction will succinctly explain the theoretical basis of the experiment and describe the method that will be used to achieve the objective. In some experiments, there is very little “theory” that can be discussed, for example, learning about a new lab technique or getting familiar with a particular piece of lab equipment. In these cases, simply describe how the technique or piece of equipment facilitates learning a new skill. However, note that many lab instruments are based on scientific principles and the student must decide whether a theoretical discussion regarding the instrument or its use is appropriate; if in doubt, ask your instructor.

Some lab reports will require a more lengthy Introduction. Some examples:

Qualitative experiments that investigate a particular type of chemical reactivity need to address in the Introduction some of the pertinent concepts and theories that are presented in Chem 141 lecture.

Experiments which involve chemical synthesis or the interconversion of one compound into another should include balanced chemical equations for each reaction that is part of the experiment; this should be part of the Introduction.

Experiments that are much more quantitative in nature will require a brief discussion of the mathematical process to be used in calculating the final results; this should be part of the Introduction.

In very simple terms:

Your method description answers the question, “how will the experiment be run?”

Your theoretical discussion answers the question, “why does this particular method apply to this experiment?”.

The length of the Introduction depends upon how much background material is included. If very little “theory” is discussed, the Introduction may be as short as one-half to three-fourths of a page. If there are several chemical equations that need to be included, the Introduction may be two to three pages in length. A well thought-out Introduction is the key to writing a good lab report; quality is more important than quantity (length). In general a short introduction is preferred.

Procedure

DO NOT COPY THE PROCEDURE FROM THE LAB MANUAL. You are not required to write out the experimental procedure. However, it is expected that the student will have read through the procedure (more than once) and understand the operations that are involved; it is essential that the student understand why each step is being done.

The only thing that needs to be written in this section is a complete reference for the procedure. Leave blank at least one-half of a page to include additions or changes (if any) that are given to you by your instructor.

Sample references in APA Style

Textbook:

Tro, N. (2008). Chemistry: A Molecular Approach (1st ed.), pp. xx-xx.  Upper Saddle River, NJ: Pearson

Prentice Hall.

Lab Manual:

Lehman, J. & Olmstead, T. et al (2002). Experiment 1: Computer Warm-Up. In Grossmont College Chemistry 141 Laboratory Manual (4^th Edition, pp. 1-3). El Cajon, California

Online Lab Manual:

Lehman, J., Olmstead, T. et al (2002). Experiment 1: Computer Warm-Up [Electronic version]. Grossmont College Chemistry 141 Laboratory Manual, 1-3.

Online Journal Article, Spreadsheet, or Directions: include author and date if known

Willard, C. (2007). Lab 1 – Error analysis, Retrieved August 16, 2007, from http://www.grossmont.edu/cwillard

Handouts: include author and date if known

Dibas, J. (2005). “Chemistry 141: Colligative Properties: Molar Mass Determined by Freezing Point Depression” [Handout 2007], Grossmont College, El Cajon, California.

Results and Calculations

The results from your experiment are always entered in this section. Recall in the Objective that you asked the question, “what is being investigated in this experiment?”. This is the place to answer that question. State your results clearly so the reader knows exactly what happened in the experiment but do not discuss the reasons for your results in this section.

Tell the reader exactly what you obtained in the experiment, for example: quantitative results from an experiment (% composition of a substance) or qualitative results (compounds A, B and C were identified as acids, D, E and F were bases).

Whenever you include statistical treatment of your data, that is a result which should be entered in this section.

Calculations (if any) are done in this section. Show all set-ups for each type of calculation; be explicit! If you must perform the same calculation more than once, you do not have to write the set-up for each one, but it should be clear as to which set-up correlates to which calculation(s). Be sure to include the final results of all calculations- consistently highlight your final answers in some fashion, draw a box around the result, double-underline the result or place final results in a table or chart.

It is a good idea to organize your results in a Table format to make it easier for the reader to understand the outcome of your experiment. If your D&O section has become messy and a bit unorganized, this is the place to “clean it up” and present it to the reader with clarity.

Discussion

The discussion is used to explain your results; the previous section is used to present the results, this section is used to discuss these results. Ask yourself provocative questions such as: Do the results make sense, is there some data missing? Did you obtain a result different from your expectations?

Sometimes the data you obtain in an experiment is straight-forward and self-explanatory. In these cases, your discussion may be brief. However, most of the time, you will need to explain to the reader why you obtained a particular result, especially if your result is different than expected.

Think of the discussion as a conclusion to your Objective and Introduction. If you have presented the objective clearly along with the theoretical background and some comments about the method to be used, then discuss your results in this context. If you posed questions in your Introduction, answer those questions here.

The discussion should also include error analysis (when appropriate): explain sources of error and how errors impact your results. Be sure to discuss only the connections between error analysis and your actual data and observations.

Include in the discussion answers to any pre or post-lab questions that have been asked in the experiment or by the instructor.

Conclusion

State the final result of your experiment in a concise and thorough manner. This section should be brief (one-paragraph).

Questions

Give the answers to any questions appearing in the lab. These may be handwritten if they involve calculations.