Bio 151: Guide to Writing Lab Reports Title: The effect of increasing the number of effervescent tablets in a volume of water on the temperature of the system. • The title is specific • The title provides an understanding of the goal of the experiment Introduction We examined the effect of increasing the number of effervescent tablets in a volume of water on the water temperature. Dissolving certain substances in water may release heat (exothermic reaction) and dissolving other substances may absorb heat (endothermic reaction). The dissolution of effervescent tablets in water is an endothermic reaction, meaning that as the effervescent tablets dissolve, heat is absorbed and the temperature of the system will decrease (MU Lab Manual, 2018). The purpose of this experiment was two-fold: to execute a simple experiment to study the scientific method, and to determine if increasing the number of effervescent tablets in a fixed volume of water will decrease the temperature of the system. We hypothesized that as the number of effervescent tablets in a solution increases, the greater the negative temperature will change. This investigation is important for learning the scientific method, as working through the steps is the most effective way to understand the scientific process (Hoffman, 2014). This method allows for the testing of a simple hypothesis, using a straightforward experimental design. • Sets the framework for the entire report and shows the readers that you understand the purpose of the study you have done. • Background information must also be included in the introduction to show why the questions was asked/hypothesis tested. • General guide for background information in the introduction. 1. Back all statements with facts. 2. Define specialized terminology. 3. Never set out to prove something, but to test or describe. 4. Keep all information relevant to your purpose. 5. Write an introduction for the study that you ENDED UP doing. Material and Methods To study the effect of increasing the number of effervescent tablets in a volume of water on the temperature of the system, we filled five 250 mL beakers with 50 mL of water, each from the same source. The beakers were labeled 0, 1, 2, 3, and 4, and stirred with a thermometer, ensuring that the water in each cup or beaker was at the same temperature. We recorded the temperature of the water in beaker 0 as the temperature with 0 tablets. We placed one effervescent tablet in beaker 1 and stirred until the solution temperature remained constant. This reading was recorded as the temperature with one tablet. After verifying that the temperature of water sample 2 had not changed, two tablets were added to beaker 2. The mixture was stirred and monitored until the temperature stabilized and the temperature reading was recorded. The same procedure was followed for three and four tablets. • Writing the materials and methods is great place to start • Provides a detailed account of the procedure that was followed in completing the experiments discussed in the report. • Serves as a set of instructions for anyone wanting to replicate the experiment(s) in the future. • Keep only the level of detail one would need to replicate the experiment. Results We examined the effect of increasing the number of effervescent tablets in a fixed volume of water on the temperature of the system. We show that increasing the number of tablets in a fixed volume of water leads to a larger decrease in water temperature (Table 1). We also observed that there is an indirect relationship between the number of tablets in solution and the temperature of the system; as the number of the tablets increase, the temperature of the system decreases (Figure 1). • Present findings in a clear, consistent, and orderly manner. • Should contain all experimental findings that will be necessary to understand the conclusion you will draw in the conclusion/discussion section. • Label every axis with the correct title and correct units. • Include a figure legend that is referenced within the text. • Do not be ambiguous, explain what you are presenting. • Do not describe the methods in this section. • Do NOT attempt to interpret the data. You can explain the trend of the data in basic terms, but you should NEVER explain the meaning of the data. It should be a statement of fact. As you can see in the example above – the data is summarized “as the number of the tablets increase, the temperature of the system decreases” but there is NO discussion of what this means – that comes later. Discussion This goal of this activity was to learn about experimental design by testing the effects of increasing the number of effervescent tablets in a fixed volume of water on the temperature of that system. We hypothesized that as the number of effervescent tablets in a solution increases, there will be a greater, negative temperature change. Based on previous research, we expected an increased negative temperature change because the reaction of the effervescent tablets with the water is endothermic, meaning the temperature of the system will decrease. We expected a greater change in water temperature with increased number of tablets, because increasing the number of the reactants (tablets) leads to a larger temperature change based on the principles of thermodynamics (Long, 2011). Our results show that increasing the number of tablets in a system leads to a larger decrease in temperature and our hypothesis is accepted. Exothermic reactions are often used as sources of power, so thermodynamic studies are important in energy production and utilization (Lincoln and Washington, 2014). Other experiments to study the thermodynamics of effervescent tablets in water could investigate the effect of the number of tablets on the rate of change (C/sec.) of a system. Nearly any other experiment could support the purpose of learning the scientific method, especially straightforward, organized experiments. • Includes restatement of hypothesis/purpose • Discuss what you expected to find/learn • Discuss how your results compared to your expectations and did they support or not support your hypothesis • Discuss any unexpected results, and talk about what they might mean or if any experimental error might have occurred. • Discuss the implications of your findings. • Discuss other experiments that could provide more/better data. References 1. Marymount University (2018). Biology 151 Lab Manual. 2. Hofmann A.H. (2014). Scientific Writing and Communication (4th Edition). New York: Oxford Press. 3. Long T. (2011). Thermodynamics of Alka-seltzer. Biochim Biophys Acta. 1572 (23), 178-186. 4. Lincoln L, Washington G. (2018). Energy usage today. Journal of Energy 13 (13), 1776-1850. • Please use this website as a guide: https://owl.purdue.edu/owl/research_and_citation/apa_style/apa_formatting_a nd_style_guide/reference_list_basic_rules.html Scientific Research: Bacterial Investigations o Design a research bacterial investigation project and complete the project proposal. o Discuss the research proposal with the instructor for approval. Students can ONLY carryout their scientific investigation once approved by the instructor. No two groups are allowed to complete the same exact experiment o Carry out student-designed experiment. o Listen to Instructor’s discussion of your scientific research semester project criteria. o Return all lab materials to work station, wipe down work area, and push in chair Disinfectants, Antiseptics, and Antibiotics Introduction Microorganisms include microscopic life forms like bacteria, fungi, and viruses (although viruses are considered non-living microbes). These organisms can live in nearly any type of environment. Microorganisms reside on and in your body, in the air, and on everything that you touch. Some microbes are not harmful to humans. We refer to these types of microbes as non-pathogenic. Nonpathogenic microorganisms include organisms like yeast. We interact with microorganisms each and every day. In fact, many are responsible for the development of certain foods. For example, we use yeast to make bread, wine, and beer for consumption. Many microorganisms are also responsible for helping in providing nutrients to plants to ensure plant growth. Some microorganisms do this by breaking down large organic compounds such as rotting wood. Although there are number of microorganisms which do not induce disease in humans, there are a number of microorganisms which do. These microorganisms are said to be pathogenic, because they can cause illness and harm to humans and in some instances other animals. Pathogenic microorganisms induce infection and disease. Examples of some infectious disease caused by pathogenic microorganisms include Staph infection, meningitis, chlamydia, food poisoning, and strep throat. Although fungi and viruses cause infection and disease, bacterial organisms tend to cause more disease and infection in humans. In order to combat infection, we rely on the use of antibiotics and disinfectants to control bacterial growth or to eradicate bacteria. The primary difference between an antibiotic and a disinfectant is that antibiotics are medicinal products which humans use to control infection in the body. Examples of antibiotics include penicillin, erythromycin, tetracycline, ampicillin, etc. Antibiotics can be taken orally by an infected patient or intravenously. They are biosynthesized products administered internally to disrupt pathogenic growth. Disinfectants are products used to prevent the spread of bacteria and other microorganisms from one human to the next. We use disinfectants to clean wounded breaches in the skin, clean table surfaces and floors, and to clean soiled clothing. Examples include Lysol, toilet scrub, and Clorox. Some disinfectants such as chlorine can cause skin irritation, so specialized disinfectants have been developed for the safe use on humans. Disinfectants which are safe for humans to use on their skin are referred to as antiseptics. Examples include mouthwash, anti-bacterial soap, hydrogen peroxide, and 70% rubbing alcohol. In this investigation, students will design an experiment involving bacteria. After reading the information on bacteria provided, students should decide what aspects of bacteria, antibiotics, and disinfectants are worthy of investigating. For instance, some companies hire scientists to test the effectiveness of their product in killing bacteria before the product is put on the market. Some companies hire scientists to collect samples of meats from different food companies to see what types of bacteria maybe growing on the food after the food has been put on the market. For this lab, the students will need to plan their experiment and carry out the experiment in the lab. is a list of materials available for students use. Below GOAL: While you will be using bacteria for your investigation, the purpose of this lab is to learn about experimental design. For that reason you must: 1. Read the brief introduction antibiotics. Using this (antibiotics, antiseptics, experiment looking at the growth. to bacteria, disinfectants, antiseptics, and information you will choose compounds or disinfectants) to begin to design an effect of various substances on bacterial 2. Knowing that you will have available to you the MATERIALS listed below, you must develop a QUESTION. If you need a little help, on the following pages there is an example protocol that you may use. a. b. c. d. e. f. g. h. i. E. coli (broth cultures) S. marcesans (broth cultures) Antibiotics Disinfectants Antiseptics Antibiotics Sterile discs Sterile swabs Nutrient agar plates 3. Once you have defined your question, you will need to develop a hypothesis. 4. Define your independent variable(s), your dependent variable(s), your positive control and your negative control. Example Experiment The following protocol may be used to aid students in developing their research projects. Below is how a student could possibly go about testing the effectiveness of a disinfectant or antibiotic against killing bacteria. 1. Obtain 3-4 sterile 1% NA petri dishes. 2. Label the bottom edge of the plate with your Group Name and bacterial strain. 3. On the bottom of the plate, draw two lines to produce 4 quadrants. 4. Label each quadrant with a number. I III II IV 5. Obtain the broth culture to be tested and a sterile swab. Dip the swab into the broth culture. 6. Gently place the swab on the nutrient agar plate and inoculate the agar plate by wiping the broth from the swab all over the plate. Be sure to cover the plate completely with the inoculate bacteria and be careful not to disrupt the agar. 7. Select disinfectants to test and record their names below. Will you be using any of the quadrants as controls? a. Quadrant I ____________________________________________ b. Quadrant II ___________________________________________ c. Quadrant III __________________________________________ d. Quadrant IV ____________________________________________ 8. Dip a pair of metal forceps into alcohol to sterilize. Allow the forceps to dry. 9. Using the sterile forceps, dip a sterile disc into one of your products. Drain the excess product from the disc and place the disk in the center of the corresponding quadrant. 10. 11. Tap the disc lightly with the forceps. Complete until your plate looks like the image below. I III II IV 12. Use a rubber band to secure all three of your plates together. Allow the plates to sit for 10 minutes undisturbed 13. Invert plates and place them in the designated rack. 14. Plates will be incubated at room temperature for one week. students will measure the growth of the bacteria. Next, week Data Collection Observe the plates. If the experiment was successful, students will see bacterial growth all over the plate. However, there should not be bacteria growing around the disc applied to the plate. To determine if the product being tested was effective in preventing the bacteria from growing, students will observe a clear ring around the disc. This clear ring can be very large or quite small. This clear ring is known as the Zone of Inhibition. This is the zone in which the disinfectant, antiseptic, or antibiotic has successfully inhibited or prevented the growth of the bacteria on the agar plate. If a product produces a big zone that means that the product is very effective in preventing the growth of the bacteria. To determine if the product is effective, students must measure the diameter of the Zone of Inhibition. To do this, students will measure the diameter of the disc used and subtract this diameter from the diameter of the clear zone surrounding the disc. The difference between the two diameters will equal the diameter of the Zone of Inhibition. Zone of Inhibition = Total Diameter (mm) – disc diameter (mm) Table 1: Zone of Inhibition (mm) for each Plate Quadrant Quadrant I II III IV Compound Applied water bleach Tea tree oil ointment Plate 1 0 8 26 6 16 20 8 14 26 6 13 24 Plate 2 0 Plate 3 0 Average 0 Interpreting Results Using your calculated average quadrant zone of inhibition (mm), categorize the outcome for each compound. Bacteria is Susceptible to product < 10 mm Bacteria is somewhat 11 – 15 mm susceptible to the product Intermediate The Bacteria tested is > 16 mm resistant to the product tested Quadrant I = ___________________________ Quadrant II = ___________________________ Quadrant III = ___________________________ Quadrant IV = ___________________________ a. What do the results suggest? b. What is the overall conclusion? c. What questions does this stimulate? What topics should students research to help answer these questions? Semester Research Project Lab Report (50 Points) After collecting the group’s experiment data, each student in the group will draft their own individual laboratory research report using the Semester Research Project Lab Report criteria provided by the instructor. This lab report is different from the other lab reports students will be writing throughout the semester. The criteria for this report is found in the document entitled, “Semester Project Assignment: Individual Lab Report” located at the end of this packet. Research Plan for Bacterial Investigation Team Members: Investigation Question and Purpose of Experiment: ____________________________________________________________________ ____________________________________________________________________ Hypothesis: ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ Identify the following variables: Dependent Variable: Independent Variable: Positive Control: Negative Control: Methods: Please describe your plan of action, in detail. ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ ____________________________________________________________________ In order to start their experiment, students must obtain the signature of their instructor acknowledging approval of the students’ semester project. Semester Research Project Approval: ___________________________________________ (Instructor Signature)
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