Many students just beginning their science education may be unfamiliar with the concept of an abstract in a lab report; it is often not required in introductory science courses because of its level of difficulty. As one takes higher level classes the teacher will specify if he or she wants an abstract to be included in the written reports. If it is required, it is the first part of your report, directly following the title page and proceeding the introduction.
The abstract, although it comes first logistically, always should be written last. It needs to be written last because it is the essence of your report, drawing information from all of the other sections of the report. It explains why the experiment was performed and what conclusions were drawn from the results obtained. A general guideline for an abstract has five sections or areas of focus: why the experiment was conducted; the problem being addressed; what methods were used to solve the problem; the major results obtained; and the overall conclusions from the experiment as a whole. Do not be misled, however, from this list into thinking that the abstract is a long section. In fact, it should be significantly shorter than all of the others. All of this information should be summarized in a clear but succinct manner if the abstract is going to be successful. An estimated average length for all of this information is only a single paragraph. Although this may seem as though it is a short length to contain all of the required information, it is necessary because it forces you to be accurate and yet compact, two essential qualities.
The best way to attempt to go about writing an abstract is to divide it into the sections mentioned above. The first two sections are very similar and can be grouped together, but do not have to be. If you decide to address them separately, make sure that you do not repeat anything. Often a section can be mentioned in only one sentence. Remember, brevity is the key to a successful abstract. Each section is addressed below to help clarify what needs to be included and what can be omitted.
The most important thing to remember when writing the abstract is to be brief and state only what is pertinent. No extraneous information should be included. A successful abstract is compact, accurate and self-contained. It also must be clear enough so someone who is unfamiliar with your experiment could understand why you did what you did, and what the experiment indicated in the end. An additional note is that abstracts typically are written in the passive voice, but it is acceptable to use personal pronouns such as I or we.
General questions to be addressed in the abstract section
1. Why it was done and what is the problem being addressed?
These two sections can be grouped together into one brief statement summarizing why the experiment was performed in the first place? What was the question trying to be answered? Science is an exploration for truth. It is all about curiosity and answering questions to find out why and how things work. The scientific method is a clear example of this; first state a problem or question and then try to determine the answer. This section is the statement of the original problem. It is the reason behind why an experiment is being done. This should not include many details, rather it should be a simple statement. It can even be stated in one or two sentences at the most.
2. What did you do?
This part of the abstract states what was done to try to answer the question proposed. It should in no way be very detailed. It contains a brief outline of what was done, highlighting only crucial steps. It is the materials and methods section of your abstract, but it is only one or two sentences in length. It is a description of how you decided to approach the problem.
3. What did you find out?
In other words, what did all of your hard work and preparation tell you about the question you set out to answer. This contains only the crucial results obtained. The crucial results are those that are necessary to answer your original question posed. Without these results, the experiment would have been useless. The results should be stated briefly and should not be explained; they should only be mentioned. It is very similar to the results section of your paper, but it highlights only pertinent results used to draw conclusions. An average length for this section is two or three sentences at the most. This number can vary however, depending on the complexity of the experiment, and so these length guides are just that, guides, not rules.
This is the end of your abstract, directly hinging on the results obtained. This is the "so what" part of your experiment. "So what" refers to what the results mean in the long run. You need not include how you drew your conclusions, only the final conclusion. This should directly follow the results so the reader knows what results led to what conclusions. This is the equivalent to the discussion part of the paper, but again, like the rest of the abstract, it needs to be stated briefly and succinctly. You do not need to explain how you deduced the conclusion from the results obtained, only the end conclusions. After you have stated this, the abstract is complete.
Here are two examples of the same abstract, sample one is an example of a badly written abstract, while sample two is an example of a well-written abstract. Italicized words are links to explanations describing why the sentences are a good or bad example of an abstract.
Sample 1: This experiment will determine what will make enzymes effective and what will make them ineffective. We tested different samples of enzymes in a spectrophotometer and recorded their absorption rates. Six samples were placed in the spectrophotometer but two contained no enzyme; these acted as blanks for the other samples. The four remaining samples contained Catecholase ranging from 0.5 ml to 1.75 m. The second half of the experiment contained four test tubes with a constant amount of Catecholase, but the pH levels ranged from four to eight. It was found that if the enzyme was present in large amounts, then the absorption rate was high, and if the pH level ranged from 6 to eight then the absorption rate was high. Therefore it can be said that enzymes work well in neutral pH levels and in large amounts.
Sample 2: This experiment was performed to determine the factors that positively influence enzyme reaction rates in cellular activities since some enzymes seem to be more effective than others. Catecholase enzyme activity was measured through its absorption rate in a spectrophotometer, using light with a wavelength of 540 nm. We compared the absorbance rates in samples with varying enzyme concentrations and a constant pH of 7, and with samples with constant enzyme concentration and varying pH levels. The samples with the highest enzyme concentration had the greatest absorption rate of 95 percent compared to the sample with the lowest concentration and an absorption rate of 24 percent. This suggests that a higher concentration of enzymes leads to a greater product production rate. The samples with a pH between six and eight had the greatest absorption rate of 70 percent compared to an absorption rate of 15 percent with a pH of 4; this suggests that Catecholase is most effective in a neutral pH ranging from six to eight.
Explanations of the Example Links
Ineffective: This sentence is in the present tense and needs to be switched to the past tense. In addition to tense problems, the sentence does not tell the reader much about what is meant by the term effective. What exactly is an effective enzyme? The author needs to be specific and try to avoid generic terms such as effective. Also, the author never states why the experiment is being conducted. Why is enzyme effectiveness so important? What makes it important enough to be studied? (return to Sample 1)
Rates: This sentence is addressing what was done, yet it barely conveys any information. The author states that different samples of enzymes were tested, but mentions nothing about the contents of the samples. Was the same enzyme used in every sample? What was in each sample, and what varied in each sample? Also, what does absorption have to do with enzyme activity? This correlation needs to be explained to the reader. One last detail that should be included is the wavelength of light that was used in the spectrophotometer. Did it remain constant or was it a variable as well? (return to Sample 1)
Eight: This is too long and detailed to be in an abstract; it sounds as though it was pulled from the methods and materials section of the paper. The amounts of enzyme do not need to be stated, nor do the pH levels. The number of samples tested do not need to be included either; it is just extraneous information that is not crucial to understanding the experiment as a whole. The information contained in this sentence can be pulled out and rearranged to say that some samples had a constant pH and varying enzyme concentrations and other samples had constant enzyme concentrations and varying pH levels. With the controls and the variables stated you can move on to your results. (return to Sample 1)
High: This is just too general, although it conveys the right information. When stating results it is okay to use actual numbers. Instead of saying that the absorption rate was high, specify how high in comparison to samples with low absorption rates. (return to Sample 1)
Amounts: An experiment is never final, nor is it ever positive. Always avoid saying that the results you obtained are correct or definite. Instead just say that the data supported or did not support your hypothesis. (return to Sample 1)
Others: This sentence is clear and concise, telling the reader why the experiment was carried out. It postulates the question of why some enzymes are more effective than others and it explains that the experiment was set up to determine what causes these differences. (return to Sample 2)
540 nm: This sentence introduces the specific enzyme being studied and how it was studied. The light wavelength used in the spectrophotometer was also specified telling the reader that wavelength was not one of the variables manipulated in the experiment. (return to Sample 2)
Levels: It is okay to use personal pronouns in the abstract and this sentence uses "we" effectively. It also defines what was done without going into great detail. The controls and the variables are stated clearly and succinctly so the reader knows what factors are being tested to determine enzyme productivity. (return to Sample 2)
Clear summary: These two sentences combine the results with the conclusion. This helps to make the conclusions drawn from the results very clear to the reader. The author also stated concrete numbers in the results so the reader is aware of just how much the absorption rates changed in each sample. (return to Sample 2)
All citations from Pechenik, Jan A. A short guide to writing about Biology. pp. 54-102, Tufts University: Harper CollinsCollege Publishers. 1993.