Formal Lab Report #1 – Percent Yield

If you want to be a scientist, it is not enough to be able to perform and set up labs. You must be able to communicate your findings and persuade others that what you found in your experiment is important. One of the main ways that we can practice our skills of communicating our results in an experiment is through a formal lab report.

Formal lab reports mimic the format that scientists use to publish their findings in scientific journals. In order for scientists to have their research accepted, they must be published in these journals. Therefore, we need to start working on our writing skills so that we are able to clearly and concisely defend our findings through our writing.

You will be writing a formal lab report on the lab that will be divided into four sections:

  1. Introduction
  2. Materials and Procedures
  3. Results
  4. Discussion

How to Write An Introduction

The introduction section of the lab report is your chance to convince your reader why what you did in your experiment is important. In order to write a good introduction, you need to have the following components within this section:

  • Background information for the topic that you were studying
  • A clear purpose for the lab that you are performing
  • Hypothesis for the experiment

You should begin the introduction section by introducing any and all background information for what you are examining in your experiment. You need to provide the reader with enough background so that they can understand the biological focus of your experiment. You should make sure to answer the following questions in your background information paragraphs:

  • What biology topics were covered in the lab that you performed?
  • What information did you need to find and why
  • How is this information important in our everyday lives and in other biology topics (i.e. what other parts of life besides the area studied in the lab would you use these concepts?

After you have introduced the background information for the lab you should focus the reader’s attention to the specific purpose of the lab. This should be no longer then a paragraph. It should answer the following questions:

  • What was the purpose of the specific lab that you did?
  • How did you use the background information to carry out the lab?
  • What was the final goal of the lab?

Finally, the last paragraph should inform the reader what your hypothesis was. This does not have to be a very long paragraph, but it should clearly and concisely state the hypothesis. Just a quick note on hypothesizes:

  • A hypothesis is an educated guess about what should occur in the lab. This hypothesis needs to be testable.
  • This is a possible solution to the purpose that you discussed previously
  • The hypothesis should be written in the form: “If ______, then ______” or “It was predicted that ______because of ______”.

Grammar for Introductions

The following grammar rules should be followed for introductions:

  • You should only use 3rd person. NEVER use 1st or 2nd person. This means you cannot say I, me, we, us, etc.
  • If you used outside sources in your background information they need to cited using the correct format (MLA or APA).
  • You should have multiple paragraphs

Example Introduction

Introduction

Scientists often predict the amount of information that they are going to form in a reaction through the use of stoichiometry. Often times, an experiment is run and scientists obtain a different amount of product then was predicted through stoichiometry. Therefore, it is necessary to calculate the difference between what was predicted to form and what actually formed. This is known as calculating the percent yield. The percent yield for any reaction is calculated by dividing what was obtained in an experiment by what was predicted to form. This yield can be described by the equation:

By calculating the percent yield, multiple aspects of the experiment that was performed can be analyzed. From the percent yield, potential sources of error and areas where there were problems with the experimental design can be identified. Many important things can be learned from the percent yield and it is an invaluable tool in countless chemistry experiments.

This lab focused on the application of the principle of percent yield. In order to study this principle, the reaction between baking soda and vinegar was utilized. When baking soda and vinegar are combined, the following reaction occurs:

NaHCO3 (s) + HC2H3O2 H2O (l) + CO2 (g) + NaC2H3O2 (aq)

Because the initial amounts of vinegar (HC2H3O2) and baking soda (NaHCO3) were known, the amount of CO2 that should form was predicted. By capturing the CO2 gas that was actually formed when baking soda and vinegar react, the actual yield of CO2 can be determined. By comparing the actual amount of CO2 that was produced and the theoretical amount of CO2 that should be produced, the percent yield can be determined for this lab. From this percent yield, possible sources of error and ways in which to improve the experimental model can be identified and discussed.

From the information that was predicted for the lab it was predicted that the percent yield would be lower then 100% because of the way the experiment was designed and because of the inaccuracy of the tools that were used to measure the volume of CO2.
How to Write a Materials and Procedure Section

The materials and procedure section tells your reader exactly what you did during the experiment and what you used to perform this experiment. This should be written so that the reader could complete the entire lab by only reading your report.

Often times, students simply copy the procedure from the handout that they were given. THIS IS NEVER OKAY. First, copying without giving credit is plagiarism. Second, you did not do everything that was done in the procedure. You performed the lab slightly different from the way that it was written. Therefore, you need to describe the way that you performed the lab, not the way you were supposed to perform the lab.

This section should be thorough, but it also does not need to contain every single detail of what you did. If you could perform the experiment again by only using what you have written, then you have written an adequate procedure.

Some quick tips for writing a good materials and procedure section:

  • Do not number your steps. What you did should be written in paragraph format and it should be multiple paragraph (group steps that were similar and put them in a single paragraph).
  • Make sure you list all the materials that you used at the beginning of the section.
  • You should cite the original source of the lab report (MAEDA Chemistry 2011)

Grammar for Materials and Procedures

The following grammar rules should be followed for introductions:

  • You should only use 3rd person. NEVER use 1st or 2nd person. This means you cannot say I, me, we, us, etc.
  • If you used outside sources in your background information they need to cited using the correct format (MLA or APA). For the first report the only outside source you need for this section is the original handout, but you should cite that you used it!
  • You should have multiple paragraphs

How to Write a Results Section

In the results section, you provide all the data that you collected and the answers to all the calculations that you performed during the lab. You do not make conclusions or interpret your data in this section. All you do is report the data that you found.

In this section, you should have all graphs and tables that convey the data that you found. All data should be reported in a table. This table should have borders around it (borders for the table can found in the toolbox under borders and shading). Units should not be attached to the number. Units should be next to the title of the column. A correct table would look like:

Length of room (cm) / 22.3
Mass of Copper (g) / 52
Volume of Water (mL) / 10.3

All tables and graphs should have a title. It should follow the format Table #: Title of the Table. You should number the table sequentially. This means that you should number the first table table1 and every table after that should increase in number.

One of the biggest mistakes that students make is that they interpret their data and draw conclusions from their data. In your results section you should only report what you found or calculated in this section. Save interpretation of your data for the discussion section of your report.

Graphs are often a good way to tell your reader about the data that you found. While not all lab reports require graphs, many reports will have a graph if you are comparing different test groups to one another. You will get a more specific handout on graphs when you have a report that requires you to produce a graph.

Grammar for Materials and Procedures

The following grammar rules should be followed for introductions:

  • You should only use 3rd person. NEVER use 1st or 2nd person. This means you cannot say I, me, we, us, etc.
  • You should have multiple paragraphs
  • Every number that you report should have a unit. Numbers without units are incorrect.
  • Don’t forget that you need to report the results of any and all calculations.

How to Write a Discussion Section

The discussion section of your report is the most important section of your report. In this section you interpret the data and draw conclusions. Your discussion section should contain the following parts:

  • Conclusions that you can draw from the data that you obtained from the lab.
  • Answers to the post-lab questions
  • Sources of error that could have altered the results that you got.

The first part of the discussion section should contain a paragraph stating clearly and concisely the conclusions that you can draw from the data that you collected. Your conclusion needs to be supported by the data that you collected.

The second part of the discussion section should contain answers to the post-lab questions. Every lab you do will have some post-lab questions. You need to answer these questions in paragraphs. Your answers should be clear and you need to explain why you are answering the way that you do.

Finally, you should discuss any sources of error that could have contributed to the results that you got during the lab. You need to talk about both human and experimental error. This means that you cannot just focus on errors that were the result of human error. You always must discuss error that happened because of the way the experiment was designed.

Grammar for Materials and Procedures

The following grammar rules should be followed for introductions:

  • You should only use 3rd person. NEVER use 1st or 2nd person. This means you cannot say I, me, we, us, etc.
  • You should have multiple paragraphs.
  • Do not number the post-lab questions. Answer these in paragraphs.

LABS AND PROJECTS