Turn to the The Coke Lab (pg 56) in the DVC CHEM 120 Lab Manual. Please read through the background on error analysis (pg 57-60) before watching the prelab videos.
Watch the following Prelab video on error in measurement and fill out the prelab notes as you go along:
Error in Measurement (Links to an external site.)
View the following videos to learn functionalities in Excel that will help you complete the analysis for the Snapple and Diet Snapple data sets. Write any notes in the space below.
Orientation to the Class Data Spreadsheet for this assignment (Links to an external site.)
Sorting Data and Formatting Cells in Excel (Links to an external site.)
Performing Calculations from Preprogrammed Functions in Excel (Links to an external site.)
Programming Functions in Excel (Links to an external site.)
(Links to an external site.)Showing Formulas in Excel (Links to an external site.)
Performing the Q test on a large data set in Excel (Links to an external site.)
Download the class data spreadsheet from Canvas by clicking this link.Preview the document You must take the class sets for BOTH Snapple tab and Diet Snapple tab and do the following in Excel:
Sort the cells to display the values from smallest to largest.
Format the cells to display the proper number of significant figures for the density calculated by each volume measuring method.
Apply the Q test calculations to both data sets to determine if any data point is an outlier and can be excluded from analysis. LIST any data point that you excluded in the spreadsheet by that label. DELETE any value you determined could be excluded by the Q-test. Note: Calculated values will automatically change when you delete outliers!
Create a table in the Excel spreadsheet with calculated values using programmed functions (Average and Standard Deviation) and user-created formulas (% Error and % Relative Standard Deviation) for each data set. The true density value for Snapple is 1.033 g/mL. The true density value of Diet Snapple is 0.998 g/mL. The lab manual tells you the true values of Coke and Diet Coke!
Review the calculated values (corrected by exclusion using the Q test), and Type your answer to the following Post-Lab Questions in a Word Document. See rubric for grading.
What is the significance of three standard deviations from an average for a set of data. Using your understanding of this significance and the calculated values from this laboratory, determine if the following two numbers are densities of coke, diet coke, or neither: 1.005 g/mL, 1.020 g/mL. Explain using the terms average, standard deviation, and probability.
Using the Snapple and Diet Snapple scatter graphs in the class data spreadsheet, rate the precision and accuracy for each of the three density determinations. The actual density of Snapple and Diet Snapple are 1.033 g/mL and 0.998 g/mL respectively. Use descriptive words about the appearance of the graph. This is a qualitative analysis of precision and accuracy.
Compare and contrast the mathematical approach to determining accuracy and precision (the calculated values or quantitative analysis) with the graphical approach (the scatter plot and qualitative analysis). Do you observe visual differences in the data’s quality relative to the calculated values alone? Explain.
Would it be more precise to transfer 25.00 mL (note sig figs) using a 25 mL volumetric pipet or a 50 mL buret having an uncertainty ±0.02 mL buret? Consider the buret requires two measurements. Explain in 2-3 complete sentences with a discussion of uncertainty in your explanation.
How do the experimental density values compare to the accepted values reported in the lab? Why might the experimental values be low especially for the graduate cylinder? Explain in 2-3 complete sentences. Use a description of error in your explanation. You should use the term random or systematic error, and the error you describe should explain why the experimental values are LOW!
Lab Report Expectations: Upload the Class Data spreadsheet including your data sort, calculations, Q test results, and graphs. Also Upload a word document or PDF with your answers to the assigned post lab question (TYPED) for a total of 2 files. For instructions on how to upload multiple files to Canvas, click here (Links to an external site.).
Peer Review: This assignment includes a peer review. You will be assigned 2 peer reviews with this assignment. That means after the due date for this assignment, Canvas will assign you two peers to review. To learn more about how to give and receive feedback in a Peer Review, click here (Links to an external site.). (In a separate assignment, you will be allowed to edit your post lab questions incorporating the peer review feedback and resubmit your responses. Please review all of your feedback!) To complete the peer review, do the following:
(2 pt) Provide 2 or more annotations within your peer’s Post Lab Question document submission that tell your peer ways they could make their language clearer or to correct their analysis.
(1 pt) Provide 1 overall comment in the comment box for your peer based on your impressions of their submission.
There are a total of 6 points associated with this peer review process (3 points for each peer review) in this assignment rubric.
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