Biology Chapter 1 Surface Tension Lab

How is the Surface Tension of Water Affected By Soap? The purpose of this lab is to help you develop scientific skills. A grading rubric is provided at the end for your information. Read the set of instructions below and then design and complete your own experiment using the Scientific Method. Type a final, formal lab report with your lab partner that includes a data table and graph formatted in Excel. Introduction: Surface tension refers to water's ability to "stick to itself". Surface tension can be measured and observed by dropping water (drop by drop) onto a penny. The number of water drops that can fit on a penny will surprise you. 1. Initial Observation: Observe surface tension by seeing how many drops of water can fit on a penny. Number of Drops ___________ Question/Problem: How does soap affect the water's surface tension? 2. Develop a hypothesis that answers the experimental question. Write your hypothesis below. 3. Test your hypothesis (design an experiment) by comparing the number of drops of tap water that can fit on a penny to the number of drops of soapy water that can fit on a penny. Because water drops may vary depending on how well you drop the water, it is best to run many trials and take an average. Establish a procedure early and follow it exactly each time. Here is an example of a data table: (you should determine the actual number of trials on your own, as you design your experiment) Trial 1 Trial 2 Trial 3 Trial 4 Trial 5 Average Tap Water Soapy Water 4. Graph and analyze the data, using an Excel spreadsheet. 5. Write a conclusion (using complete sentences!) that explains how soap affects the surface tension of water, using your data to help you answer the question. Next, suggest a legitimate reason for your observations (in other words, why did it happen?). You may need to complete some research into the properties of water to help explain these conclusions. Finally, support or reject your hypothesis.

Lab Report Template Title: * a brief, concise, yet descriptive title Background: This is where you provide some background and state the problem. What question are you trying to answer? Include any preliminary observations that you’ve made as well as any background information about the subject that will help the reader understand your investigation. Hypothesis: Write a possible solution for the problem. Make sure this possible solution is a complete sentence. Make sure the statement is testable. Materials: Make a list of ALL items used in the lab. Procedure: Write a paragraph (complete sentences) which explains what you did in the lab. Be sure to thoroughly explain your methods and strategies. For instance, why were many trials taken and averaged? Don’t forget to identify your control group and your experimental group, if appropriate. It is OK to provide a step-by-step (numbered) set of directions. The idea here is that ANYONE could test your results by repeating the experiment in the same way that you did. Results (Data): This section should include any data tables, observations, or additional notes you make during the lab. Tip: When graphing data, the independent variable typically goes on the X-axis. Before you graph the data, be sure to identify the independent variable and the dependent variable in the experiment, and them place them on the appropriate axes. Confused? The dictionary defines an independent variable as a hypothesized cause or influence on a dependent variable. In other words, the independent variable is the variable that you manipulate in the experiment. The dependent variable “depends” on the independent variable. Another tip: If you created your graphs in Excel, you should import them into the body of the lab report rather than attaching them at the end of the report. (Attachments interrupt the flow of the report.) The headings in your report should follow the order of the Scientific Method. All tables, graphs and charts should be titled and labeled appropriately. They should be designed to be self-explanatory.

Analysis: If you completed any calculations during the investigation, at least one example of the calculations should be shown in the Analysis section. In this simple experiment, you will simply show how the trials were averaged. In other experiments, you may need to show formulas or steps related to your analysis of the data. In addition, the analysis section should help the reader interpret the trends that are portrayed in the graphs. Conclusions: Accept or reject your hypothesis. EXPLAIN why you accepted or rejected your hypothesis based on the data from the lab. Include a summary of the data - averages, highest, lowest., etc. to help the reader understand your results List one thing you learned and describe how it applies to a real-life situation. Discuss possible errors that could have occurred in the collection of the data (experimental errors) and suggestions for further study

Extension: What if the experimental question was "How does salt affect the surface tension of water?" Describe how you would answer this question using the scientific method. If you have time, you can test this. Lab Report Rubric (4 pts) Excellent

(3 pts)

(2 pts)

(1 pt)

(0)

1. Title is relevant and descriptive 2. First section includes the question to be answered by Title, the lab Background 3. background research and and/or sound reasoning Hypothesis sets the stage for the experiment 4. Hypothesis (prediction) is testable.

One of the "excellent" conditions is not met

Two of the "excellent" conditions is not met

Three of the "excellent" conditions is not met

missing

1. Methods and strategies are explained 2. A thorough step- bystep list of how the experiment was performed is provided or a clear narrative of the procedure is provided

Both criteria are provided but clarity is lacking

Only a description or step-by-step list of how the experiment was performed

Procedure couldn't be repeated

missing

Results and data are clearly recorded, organized so it is easy for the reader to see trends. All appropriate

Results are clear and labeled, trends are

Results are unclear, missing labels, trends are not obvious at all

Results are present, though too disorganized or poorly

Methods

Results (data)

missing

labels are included

Analysis

Analysis somewhat lacking in The data and observations insight, are analyzed accurately, enough trends are noted, enough data, data was taken to establish though conclusion additional data would be more powerful

1. Summarizes the essential data used to draw conclusions 2. Conclusions follow data (not wild guesses or leaps of logic), 3. Discusses applications of Conclusions experiment ("real world" connections) 4. Hypothesis is rejected or accepted based on the data 5. Sources of error acknowledged 6. Suggestions for further study

Format of report

not obvious

One of the "excellent" conditions is not met

recorded to make sense f

Analysis lacking in insight, not enough data was gathered to establish trends, OR analysis does not follow data

Analysis poor, not enough data, missing inaccurate analysis

Two of the "excellent" conditions is not met

Three of the "excellent" conditions is not met

Typed neatly, organized with headings, headings “follow” the steps of the Scientific Method, few spelling/grammar errors

Somewhat lacking in organization, multiple spelling/grammar errors, not neat, lack of effort

* this lab report format was adapted from Biologycorner.com

missing