MicroBiology LabPaq / Published by: Hands-On Labs, Inc.

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A laboratory Manual of Small-Scale Experiments for the independent Study of

Microbiology

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Phone: Denver Area: 303-679-6252 Toll-free, Long-distance: 866-206-0773

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Printed in the United States of America.

The experiments in this manual have been and may be conducted in a regular formal laboratory or classroom setting with the users providing their own equipment and supplies. However, this manual was especially written for the benefit of the independent study of students who do not have convenient access to such facilities. It allows them to perform college and advanced high school level experiments at home or elsewhere by using a LabPaq, a collection of experimental equipment and supplies specifically packaged to accompany this manual.

Use of this manual and authorization to perform any of its experiments is expressly conditioned upon the user reading, understanding and agreeing to fully abide by all the safety precautions contained herein.

Although the author and publisher have exhaustively researched many sources to ensure the accuracy and completeness of the information contained in this manual, we assume no responsibility for errors, inaccuracies, omissions or any other inconsistency herein. Any slight of people, organizations, materials, or products is unintentional.

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Table of contents 5 Important Information to Help Students with the Study of Microbiology

Experiments 49 observing Bacteria and Blood

73 Bacterial Morphology

86 Aseptic Technique & Culturing Microbes

105 Isolation of Individual Colonies

129 Differential Staining

141 Methyl red Voges-Proskauer Test

153 Antibiotic Sensitivity

167 Microbes in the Environment

Appendix 178 Preparation of Cultures

181 Preparation of Disinfecting Solution

183 Final Cleanup Instructions

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Important Information to Help Students with the Study of Microbiology

Welcome to the study of microbiology. Do not be afraid of taking this course. By the end of the semester you will be really proud of yourself and will wonder why you were ever afraid of the m-word, microbiology! After their first microbiology class, most students say they thoroughly enjoyed it, learned a lot of useful information for their lives, and only regret not having studied it sooner.

Microbiology is not some “mystery” science only comprehendible by eggheads. Microbiology is simply the study of microscopic living organisms. It will be easier for you to understand the world we live in and to make the multitude of personal and global decisions that affect our lives and our planet after you have learned about the characteristics of life around you and how organisms change and interact with each other, with the environment, and with you. Plus, having microbiology credits on your transcript will certainly be impressive, and your microbiology knowledge may create some unique job opportunities for you.

This lab manual of microbiology experiments was designed to accompany any entry level college or advanced high school level microbiology course. It can be used by all students, regardless of the laboratory facilities available to them. Its experiments have been and continue to be successfully performed in regular microbiology laboratories. With the special LabPaq experiments can be performed at home by independent-study students or at small learning centers that do not have formal laboratories. Throughout the manual there are references about campus-based and independent study, but all of the information and references herein are equally relevant to both types of students.

Introduction

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Micro- and Small-Scale Experiments You may be among the growing number of students to take a full-credit microbiology course through independent study. If so, you can thank the development and perfection of micro- and small-scale techniques in microbiology experimentation. Experimentation is essential and fundamental to fully understanding the concepts of microbiology. In the past, microbiology courses required that all classes be conducted on a campus because experiments had to be performed in the campus laboratory. This was due in part to the potential hazards inherent in some traditional experimentation.

These elements of danger, plus increasing chemical and material costs and environmental concerns about chemical and biological material disposal, made high schools, colleges, and universities reexamine the traditional laboratory methods used to teach subjects such as chemistry and microbiology. Scientists began to scale down the quantities of chemicals used in their experiments and found that reaction results remained the same, even when very tiny amounts of chemicals were used. Institutions also discovered that student learning was not impaired by studying small- sized reactions.

Over time, more and more traditional chemistry and microbiology experiments were redesigned for micro- and small-scale techniques. One of the primary pioneers and most prominent contributors to micro- and small-scale experimentation is Dr. Hubert Alyea of Princeton University. He not only reformatted numerous experiments, he also designed many of the techniques and equipment used in micro- and small-scale chemistry and microbiology today.

With decreased hazards, costs, and disposal problems, micro- and small-scale experimentation techniques were quickly adapted for use in scholastic laboratories. As these techniques continued to be further refined it became possible to perform basic experiments in the classroom and eventually outside the classroom. This slow but steady progression of micro- and small-scale techniques makes it possible for independent study students to take a full-credit microbiology course since they can now perform experiments at home.

Introduction

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How to Study Microbiology Microbiology is not the easiest subject to learn, but neither is it the hardest. As in any other class, if you responsibly apply yourself, conscientiously read your text, and thoughtfully complete your assignments, you will learn the material. Here are some basic hints for effectively studying microbiology – or any other subject – either on or off campus.

Plan to Study: You must schedule a specific time and establish a specific place in which to seriously, without interruptions or distractions, devote yourself to your studies. Think of studying like you would think of a job, except that now your job is to learn. Jobs have specific times and places in which to get your work done, and studying should be no different. Just as television, friends, and other distractions are not permitted on a job; you should not permit them to interfere with your studies. You cannot learn when you are distracted. If you want to do something well, you must be serious about it. Only after you’ve finished your studies should you allow time for distractions.

get in the right Frame of Mind: Think positively about yourself and what you are doing. Give yourself a pat on the back for being a serious student and put yourself in a positive frame of mind to enjoy what you are about to learn. Then get to work! Organize any materials and equipment you will need in advance so you don’t have to interrupt your thoughts to find them later. Look over your syllabus and any other instructions to know exactly what your assignment is and what you need to do. Review in your mind what you have already learned. Is there anything that you aren’t sure about? Write it down as a formal question, then go back over previous materials to try to answer it yourself. If you haven’t figured out the answer after a reasonable amount of time and effort, move on. The question will develop inside your mind and the answer will probably present itself as you continue your studies. If not, at least the question is already written down so you can discuss it later with your instructor.

Be Active with the Material: Learning is reinforced by relevant activity. When studying feel free to talk to yourself, scribble notes, draw pictures, pace out a problem, tap out a formula, etc. The more active things you do with study materials, the better you will learn. Have highlighters, pencils, and note pads handy. Highlight important data, read it out loud, and make notes. If there is a concept you are having problems with, stand up and pace while you think it through. See the action taking place in your mind. Throughout your day try to recall things you have learned, incorporate them into your conversations, and teach them to friends. These activities will help to imprint the related information in your brain and move you from simple knowledge to true understanding of the subject matter.

Do the Work and Think about What you are Doing: Sure, there are times when you might get away with taking a shortcut in your studies, but in doing so you will probably shortchange yourself. The things we really learn are the things we discover ourselves. That is why we don’t learn as much from simple lectures or when someone gives us the answers. And when you have an assignment, don’t just go through the motions. Enjoy your work, think about what you are doing, be curious, examine your results, and consider the implications of your findings. These “critical thinking” techniques will improve and enrich your learning process. When you complete your assignments independently and thoroughly you will have gained knowledge and you will be proud of yourself.

Introduction

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How to Study Microbiology Independently There is no denying that learning through any method of independent study is a lot different than learning through classes held in traditional classrooms. A great deal of personal motivation and discipline is needed to succeed in a course of independent study where there are no instructors or fellow students to give you structure and feedback. But these problems are not insurmountable and meeting the challenges of independent study can provide a great deal of personal satisfaction. The key to successful independent study is in having a personal study plan and the personal discipline to stick to that plan.

Properly Use your learning Tools: The basic tools for telecourses, web courses and other distance-learning methods are often similar and normally consist of computer software or videos, textbooks, and study guides. Double check with your course administrator or syllabus to make sure you acquire all the materials you will need. These items are usually obtained from your campus bookstore, library, or via the Internet. Your area’s public and educational television channels may even broadcast course lectures and videos. If you choose to do your laboratory experimentation independently, you will need the special equipment and supplies described in this lab manual and contained in its companion LabPaq. The LabPaq can be purchased on the Internet at www. LabPaq.com.

For each study session, first work through the appropriate sections of your course materials. These basically serve as a substitute for classroom lectures and demonstrations. Take notes as you would in a regular classroom. Actively work with any computer and/or text materials, carefully review your study guide, and complete all related assignments. If you do not feel confident about the material covered, repeat these steps until you do. It’s a good idea to review your previous work before proceeding to a new section. This reinforces what you previously learned and prepares you to absorb new information. Experimentation is the very last thing done in each study session and it will only be really meaningful if you have first absorbed the text materials that it demonstrates.

Plan to Study: A regular microbiology course with a laboratory component will require you to spend around 15 hours a week studying and completing your assignments. Remember, microbiology is normally a 5-credit hour course! To really learn new material there is a generally accepted 3-to- 1 rule that states that at least 3 hours of class and study time are required each week for each hour of course credit taken. This rule applies equally to independent study and regular classroom courses. On campus, microbiology students are in class for 4 hours and in the laboratory for 2 to 3 hours each week. Then they still need at least 8 hours to read their text and complete assignments. Knowing approximately how much time you need will help you to formulate a study plan at the beginning of the course and then stick with it.

Schedule your Time Wisely: The more often you interact with study materials and call them to mind, the more likely you are to reinforce and retain the information. Thus, it is much better to study in several short blocks of time rather than in one long, mind-numbing session. Accordingly, you should schedule several study periods throughout the week, or better yet, study a little each day. Please do not try to do all of your study work on the weekends! You will just burn yourself out, you won’t really learn much, and you will probably end up feeling miserable about yourself and microbiology. Wise scheduling can prevent such unpleasantness and frustration.

Introduction

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Choose the Right Place for Your Home Laboratory If you are experimenting at home, the best place to perform your micro- and small-scale microbiology experiments is in an uncluttered room that has these important features:

● a door that can be closed to keep out pets and children

● a window or door that can be opened for fresh air ventilation and fume exhaust

● a source of running water for fire suppression and cleanup

● a counter or table-top work surface

● a heat source such as a stove top, hot dish, or Bunsen burner

The kitchen usually meets all these requirements, but you must make sure you clean your work area well both before and after experimentation. This will keep foodstuff from contaminating your experiment and your experiment materials from contaminating your food. Sometimes a bathroom makes a good laboratory, but it can be rather cramped and subject to a lot of interruptions. Review the “Basic Safety” section of this manual to help you select the best location for your home-lab and to make sure it is adequately equipped.

Introduction

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Organization of the Lab Manual Before proceeding with the experiments you need to know what is expected of you. To find out, please thoroughly read and understand all the various sections of this manual.

laboratory Notes: Like all serious scientists you will record formal notes detailing your activities, observations, and findings for each experiment. These notes will reinforce your learning experiences and knowledge of microbiology. Plus, they will give your instructional supervisor a basis for evaluating your work. The “Laboratory Notes” section of this manual explains exactly how your lab notes should be organized and prepared.

Required Equipment and Supplies: This manual also contains a list of the basic equipment and supplies needed to perform all the experiments. Students performing these experiments in a non-lab setting must obtain the “LabPaq” specifically designed to accompany this manual. It includes all the equipment, materials, and chemicals needed to perform these experiments, except for some items usually found in the average home or obtainable in local stores. At the beginning of each experiment there is a “Materials” section that states exactly which items the student provides and which items are found in the LabPaq. Review this list carefully to make sure you have all these items on hand before you begin the experiment. It is assumed that campus- based students will have all the needed equipment and supplies in their laboratories and that the instructors will supply required materials and chemicals in the concentrations indicated.

Laboratory Techniques: While these techniques primarily apply to full-scale experiments in formal laboratories, knowledge of them and their related equipment is helpful to the basic understanding of microbiology and may also be applicable to your work with micro- and small- scale experimentation.

Basic Safety and Micro-scale Safety reinforcement: The use of this lab manual and the LabPaq, plus authorization to perform their experiments, are expressly conditioned upon the user reading, understanding and agreeing to abide by all the safety rules and precautions noted. Additional terms authorizing use of the LabPaq are contained in its purchase agreement. These safety sections are relevant to both laboratory and non-laboratory experimentation. They describe potential hazards plus the basic safety equipment and safety procedures designed to avoid such hazards. The Basic Safety and Micro-scale Safety Reinforcement sections are the most important sections of this lab manual and should always be reviewed before starting each new experiment.

Experiments: All experimental materials and procedures are fully detailed in the laboratory manual for each experiment. Chemicals and supplies unique for a specific experiment are contained in a bag labeled with the experiment number.

Introduction

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How to Perform an Experiment Although each experiment is different, the process for preparing, performing, and recording all the experiments is essentially the same.

Review Basic Safety: Before beginning reread the safety sections, try to foresee potential hazards, and take appropriate steps to prevent problems.

Read through the Entire Experiment before You Start: Knowing what you are going to do before you do it will help you to be more effective and efficient.

Organize Your Work Space, Equipment, and Materials: It is hard to organize your thoughts in a disorganized environment. Assemble all required equipment and supplies before you begin working. These steps will also facilitate safety.

outline your lab Notes: Outline the information needed for your lab notes and set up required data tables. This makes it much easier to concentrate on your experiment. Then simply enter your observations and results as they occur.

Perform the Experiment According to Instructions: Follow exactly all directions in a step-by-step format. This is not the time to be creative. DO NOT attempt to improvise your own procedures!

Think About What you Are Doing: Stop and give yourself time to reflect on what has happened in your experiment. What changes occurred? Why? What do they mean? How do they relate to the real world? This step can be the most fun and often creates “light bulb” experiences of understanding.

Complete Your Lab Notes and Answer Required Questions: If you have properly followed all the above steps, this concluding step will be easy.

clean-up: Blot any minute quantities of unused chemicals with a paper towel or flush them down the sink with generous amounts of water. Discard waste in your normal trash. Always clean your equipment immediately after use or residue may harden and be difficult to remove later. Return equipment and supplies to their proper place, and if working at home with a LabPaq, store it out of the reach of children and pets.

Introduction

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Antibiotic Sensitivity 24 – 48 hrs. ahead 1 hour 24 – 72 hours 1 hour

EXPEriMENT 11:

Fomite Transmission None 1 – 2 hours 24 – 72 hours Less than 1 hour

EXPEriMENT 12:

Microbes in the Environment None 1 – 3 hours 24 – 72 hours Less than 1 hour

EXPEriMENT 13: 24 hour intervals

Fungi None Less than 1 hour Up to 1 week 2 – 3 hours

Estimated Time Requirements for Each Experiment Note: These estimates are provided to help you plan and schedule your time. They are given per individual lab performed separately and do not consider time and step savings possible when several labs are grouped together. Of course, these are only estimates and your actual time requirements may differ.

Experiment No. / Title Preparation Experimenting Incubation After Incubation

EXPEriMENT 1:

Observing Bacteria & Blood None 3 – 4 hours None None

EXPEriMENT 2:

Bacterial Morphology None 3 – 4 hours None None

EXPEriMENT 3:

Aseptic Techniques & Culturing Microbes None 1 – 2 hours 24 – 48 hours Less than 1 hour

EXPEriMENT 4:

Isolation of Individual Colonies None-use Exp. 3 cultures 3 – 4 hours 24 – 48 hours Less than 1 hour

EXPEriMENT 5: 30 minutes

Differential Staining 24 – 48 hours ahead 3 – 4 hours 24 – 48 hours None

EXPEriMENT 6:

Methyl Red 30 minutes

Voges-Proskauer Test 24 – 48 hours ahead Less than 1 hour 48 – 72 hours 1 hour

EXPEriMENT 7: 30 minutes

Motility Testing 24 – 48 hours ahead Less than 1 hour 24 – 48 hours Less than 1 hour

EXPEriMENT 8:

Carbohydrate 30 minutes

Fermentation Testing 24 – 48 hrs. ahead Less than 1 hour 12 – 24 hours Less than 1 hour

EXPEriMENT 9: 30 minutes

Osmosis 24 – 48 hrs. ahead Less than 1 hour 24 – 72 hours Less than 1 hour

EXPEriMENT 10: 30 minutes

Introduction

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laboratory Notes and lab reports Normally two basic records are compiled during and from scientific experimentation activities. The first record is Lab Notes which you will record as you perform your actual experiments. Entries into your lab notebook will be the basis for your second record, the Lab Report. The Lab Report formally summarizes the activities and findings of your experiment and is what is normally submitted for instructor grading.

Scientists keep track of their experimental procedures and results through lab notes that are recorded in a journal-type notebook as they work. In laboratories these notebooks are often read by colleagues such as directors and other scientists working on a project. In some cases scientific notebooks have become evidence in court cases. Thus, lab notes must be intelligible to others and include sufficient information so that the work performed can be replicated and so there can be no doubt about the honesty and reliability of the data and of the researcher.

Notebooks appropriate for data recording are bound and have numbered pages that cannot be removed. Entries normally include all of the scientist’s observations, actions, calculations, and conclusions related to each experiment. Data is never entered onto pieces of scratch paper to later be transferred, but rather is always entered directly into the notebook. When erroneous data is recorded, a light diagonal line is drawn neatly through the error, followed by a brief explanation as to why the data was voided. Information learned from an error is also recorded. Mistakes can often be more useful than successes, and knowledge gained from them is valuable to future experimentation.

As in campus-based science laboratories, independent-study students are normally expected to keep a complete scientific notebook of their work that may or may not be periodically reviewed by their instructor. Paperbound 5×7 notebooks of graph paper usually work well as science lab notebooks. Since it is not practical to send complete notebooks back and forth between instructors and students for each experiment, independent-study students usually prepare formal Lab Reports that are submitted to their instructors along with regular assignments via e-mail or fax.

Lab notes of experimental observations can be kept in many ways. Regardless of the procedure followed, the key question for deciding what kind of notes to keep is this: “Do I have a clear enough record so that I could pick up my lab notebook or read my Lab Report in a few months and still explain to myself or others exactly what I did?” Laboratory notes normally include these components:

Title: This should be the same title stated in the laboratory manual.

Purpose: Write a brief statement about what the experiment is designed to determine or demonstrate.

Procedure: Briefly summarize what you did in performing this exercise and what equipment was used. Do not simply copy the procedure statement from the lab manual.

Data Tables: Tables are an excellent way to organize your observational data. Where

Introduction

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applicable, the “Procedures” section of the experiment often advises a table format for data recording. Always prepare tables before experimenting so they will be ready to receive data as it is accumulated.

Observations: What did you observe, smell, hear, or otherwise measure? Usually, observations are most easily recorded in table form.

Questions: Questions are asked frequently throughout and at the end of exercises. They are designed to help you think critically about the exercise you just performed. Answer thoughtfully.

conclusions: What did you learn from the experiment? Your conclusions should be based on your observations during the exercise. Conclusions should be written in your best formal English, using complete sentences, paragraphs, and correct spelling.

Here are some general rules for keeping a lab notebook on your science experiments:

Leave the first two to four pages blank so you can later add a “Table of Contents” at the front of the notebook. Entries into the table of contents should include the experiment number and name plus the page number where it can be found.

● Your records should be neatly written.

● The notebook should not contain a complete lab report of your experiment. Rather, it should simply be a record of what you did, how you did it, and what your results were. Your records need to be complete enough so that any reasonably knowledgeable person familiar with the subject of your experiment, such as another student or your instructor, can read the entries, understand exactly what you did, and if necessary, repeat your experiment.

● Organize all numerical readings and measurements in appropriate data tables as in the sample Lab Report presented later.

● Always identify the units for each set of data you record (centimeters, kilograms, seconds, etc.).

● Always iden tify the equipment you are using so you can find or create it later if needed to recheck your work.

● It is an excellent idea to document important steps and observations of your experiments via digital photos and also to include yourself in these photos. Such photos within your Lab Report will document that you actually performed the experiment as well as what you observed.

● In general, it is better to record more rather than less data. Even details that may seem to have little bearing on the experiment you are doing (such as the time and the temperature when the data were taken and whether it varied during the observations) may turn out to be information that has great bearing on your future analysis of the results.

● If you have some reason to suspect that a particular data set may not be reliable (perhaps you had to make the read ing very hurriedly) make a note of that fact.

Introduction

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● Never erase a reading or data. If you think an entry in your notes is in error, draw a single line through it and note the correction, but do not scratch it out completely or erase it. You may later find that it was significant after all.

Although experimental results may be in considerable error, there is never a “wrong” result in an experi ment for even errors are important results to be considered. If your observations and measurements were carefully made, your result will be correct. Whatever happens in nature, includ ing the laboratory, cannot be wrong. Errors may have nothing to do with your investigation, or they may be mixed up with so many other events you did not expect that your report is not use- ful. Yet even errors and mistakes have merit and often lead to our greatest learning experiences. Thus, you must think carefully about the interpretation of all your results, including your errors.

Finally, the cardinal rule in a laboratory is to fully carry out all phases of your experiments instead of “dry-labbing” or taking shortcuts. The Greek scientist, Archytas, summed this up very well in 380 BCE:

In subjects of which one has no knowl edge one must obtain knowledge either by learning from someone else or by discover ing it for oneself. That which is learned, there- fore, comes from another and by outside help; that which is discovered comes by one’s own efforts and independently. To discover without seeking is difficult and rare, but if one seeks it is frequent and easy. If, however, one does not know how to seek, discovery is im possible.

Introduction

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Science lab report Format This guide covers the overall format that formal Lab Reports normally follow. Remember that the Lab Report should be self-contained so that anyone, including someone without a science background and without a lab manual, can read it and understand what was done and what was learned. Data and calculation tables have been provided for many of the labs in this manual and students are encouraged to use them. Computer spreadsheet programs such as Excel® can greatly facilitate the preparation of data tables and graphs. One website with additional information on preparing lab reports is: http://www.ncsu.edu/labwrite/. Remember, above average work is necessary to receive above average grades!

Lab Reports are expected to be word processed and to look organized and professional. They should be free of grammar, syntax, and spelling errors and be a respectable presentation of your work. Writing in the first person should be avoided as much as possible. Lab Reports should generally contain these sections:

● Title Page

● Section 1: Abstract, Experiment Description, Procedures, and Observations including photos, drawings, and data tables

● Section 2: Analysis including calculations, graphs, and error analysis

● Section 3: Discussion of Results

Each of the above three sections is discussed in greater detail below. They should be clearly distinguished from each other in the actual report. The presentation and organization skills developed by producing science Lab Reports will be beneficial to all potential career fields.

Title Page: This is the first page of the lab report and consists of:

a. Experiment number and/or title

b. Your name

c. The names of any lab partner(s)

d. The date and time the experiment was preformed

e. The location should be included if work was performed in the field

f. The course number

Introduction

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Section 1: Abstract, Experiment, and Observation Abstract: Even though the abstract appears at the beginning of the report, it is written last and inserted into the beginning. An abstract is a very concise description of the experiment’s objective, results, and conclusions. It should be no longer than a paragraph.

Experiment and Observation: Carefully, yet concisely, describe, in chronological order, what was done, what was observed, and what, if any, problems were encountered. Describe what field and laboratory techniques and equipment were employed to collect and analyze the data upon which the conclusions are based. Photos and graphic illustrations are usually inserted in this section. Graphics should be in .jpg or .gif format to minimize their electronic file size.

Show all work for any calculations performed. Every graph must have a title and its axes must be clearly labeled. Curves through data points this should be “best-fit curves,” which are smooth straight or curved lines that best represents the data, rather than a dot-to-dot connection of data points.

Include all data tables, photos, graphs, lists, sketches, etc. in an organized fashion. Include relevant symbols and units with data. Generally a sentence or two explaining how data was obtained is appropriate for each data table.

Note any anomalies observed or difficulties encountered in collecting data as these may affect the final results. Include information about any errors observed and what was learned from them. Be deliberate in recording the experimental procedures in detail. Your comments may also include any preliminary ideas you have on explaining the data or trends you see emerging.

Introduction

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Section 2: Analysis including Calculations, Graphs, and Error Analysis Generally, the questions at the end of each lab will act as a guide for preparing results and conclusions. This section is normally written in paragraph form and not more than one or two pages long. Additional considerations are:

● What is the connection between the experimental measurements taken and the final results and conclusions? How do your results relate to the real world?

● What were the results of observations and calculations?

● What trends were noticed?

● What is the theory or model behind the experiment preformed?

● Do the experimental results substantiate or refute the theory? Why? Be sure to refer specifically to the results you obtained!

● Were the results consistent with your original predictions of outcomes or were you forced to revise your thinking?

● Did “errors” such as environmental changes (wind, rain, etc.) or unplanned friction occur? If so, how did they affect the experiment?

● Did any “errors” occur due to the equipment used such as estimates being skewed due to a lack of sufficient measurement gradients on a beaker?

● What recommendations might improve the procedures and results?

Errors: In a single paragraph comment on the accuracy and precision of the apparatus and include a discussion of the experimental errors and an estimate of the error in your final result. Remember, “errors” are not “mistakes!” Errors arise because the apparatus and/or the environment inevitably fail to match the “ideal circumstances” assumed when deriving a theory or equations. The two principal sources or error are:

Physical phenomena: Elements in the environment may be similar to the phenomena being measured and thus may affect the measured quantity. Examples might include stray magnetic or electric fields or unaccounted for friction.

Limitations of the observer, the analysis, and/or the instruments: Examples are parallax error when reading a meter tape, the coarse scale of a graph, and the sensitivity of the instruments.

Examples of “mistakes” and “human errors” that are not acceptable scientific errors include:

a. Misuse of calculator (pushing the wrong button, misreading the display)

b. Misuse of equipment

c. Faulty equipment

d. Incorrectly assembled circuit or apparatus

Introduction

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Section 3: Discussion, Results, and Conclusions Discussion: The discussion section should be carefully organized and include consideration of the experiment’s results, interpretation of results, and uncertainty in results as further described below. This section is normally written in paragraph form and no more than one to two pages in length. Occasionally it will be more appropriate to organize various aspects of the discussion differently for different labs. Not all of the following questions will apply to every lab.

results

● What is the connection between your observations, measurements, and final results?

● What were the independent or dependent variables in the experiment?

● What were the results of your calculations?

● What trends were noticeable?

● How did the independent variables affect the dependent variables? For example, did an increase in a given independent variable result in an increase or decrease in the associated dependent variable?

Interpretation of Results

● What is the theory or model behind the experiment you performed?

● Do your experimental results substantiate or agree with the theory? Why or why not? Be sure to refer specifically to YOUR experimental results!

● Were these results consistent with your original beliefs or were you forced to re-evaluate your prior conceptions?

Uncertainty in results:

● How much did your results deviate from expected values?

● Are the deviations due to error or uncertainty in the experimental method or are they due to idealizations inherent in the theory, or are they due to both?

● If the deviations are due to experimental uncertainties can you think of ways to decrease the amount of uncertainty?

● If the deviations are due to idealizations in the theory what factors has the theory neglected to consider? In either case, consider whether your results display systematic or random deviations.