Chem 104 Laboratory



Chem 104 Laboratory

Potato Chip Fat Content

Reference: Chemistry for a Modern Society Laboratory Manual, Wayne M. Stalick, 2003, Pages 143-146.

Data: After you are done with the experiment and have recorded the mass of fat in your samples (regular and low fat/non fat) in the lab, enter your data into the database. In your measurements and calculations pay a close attention to uncertainties and significant figures.

Results: Outside of the class you are able to retrieve your data along with that of the entire class by going to the website and entering your ID (your GMU email address) and password (your SS#). The retrieval page is in the form of an Excel spreadsheet. You will use Excel to calculate the mass of fat in the regular chips and low fat/non fat chips, the mass percent of fat for both type of chips, and the percent difference between your mass percent and that that appears on the package.

Your Excel report should include the following:

• The downloaded retrieval Excel spreadsheet called “Rawdata” which shows the data for the entire class. Make sure that you round the numbers in each column to the appropriate significant figures. A typical example of a RawData sheet is shown below:

Table 1: RawData:

| |A |B |C |D |E |F |

|1 |Mass empty (reg) g |Mass full (reg)|Mass chip (reg) g|Mass empty |Mass full |Mass chip |

| | |g | |(low/non) g |(low/non) g |(low/non) g |

|2 |25.21 |25.331 |0.523 |25.21 |25.442 |0.523 |

|3 |27.41 |27.552 |0.502 |27.41 |27.666 |0.502 |

|4 |26.32 |26.506 |0.554 |26.32 |26.609 |0.554 |

|5 |24.65 |24.826 |0.568 |24.65 |24.915 |0.568 |

• You need to show your calculated results on a separate spreadsheet called “ClassResults”. Go to Sheet2 of the Excel document and right click on this tab and name it Classresults. Here is an example of such sheet:

Table 2: ClassResults:

|A |B |C |D |E |F |G |H |I | |1 | |mass of fat (reg) g |mass of fat (low) g |Exp.%fat (reg) |Exp.%fat (low/non) |Theo.% fat (reg) |Theo. % fat (low/non) |%errorf. (reg) |%error. (low/non) | |2 | |0.232 |0.121 |44.35 |23.13 |56.53 |30.24 |21.53 |23.49 | |3 | |0.256 |0.142 |50.99 |28.28 |56.53 |30.24 |9.800 |6.464 | |4 | |0.289 |0.186 |52.16 |33.57 |56.53 |30.24 |7.731 |11.01 | |5 | |0.265 |0.176 |46.65 |30.98 |56.53 |30.24 |17.479 |2.460 | |6 |Average = |0.260 |0.156 |48.54 |28.99 | | | | | |7 |Std. Dev. = |0.0235 |0.0301 |3.661 |4.466 | | | | | |

In order to calculate the mass of fat in the regular chips, in cell B2 type =(RawData!B2-RawData!A2); the RawData values are from Table 1 above. Go to the bottom right corner of cell B2 and drag down to obtain mass of fat in the regular chips for the entire class. In column C you need to calculate the mass of fat in the low/non fat chips. Go to cell C2 and type in =(RawData!E2-RawData!D2). Now you need to calculate the % mass of fat for regular chips. The formula for %mass is (mass of fat/mass of chip)*100; therefore, in cell D2 type =(B2/RawData!C2)*100. For low/non fat chips type the same equation in cell E2 except instead of B2 put in C2 and instead of C2 put in F2 (=(C2/RawData!F2)*100). Go to the bottom right corner of this cell and drag down to get the data for the entire class. The columns D and E give you the experimental %mass of fat in the chips. Now you need to calculate %mass of fat based on the data from the chips’ package. In this sample calculation we assume that net weight of regular chips was 28.3g and fat content was 16g, and those of low/non fat chips were 49.6g and 15g respectively. To calculate %mass of fat (regular) type this formula in cell F2 =(16/28.3)*100. This value would be the same for all the data points, so go to the lower right hand corner of cell F2 and drag down. Do the same for low/non fat chips: type =(15/49.6)*100 in cell E2 and drag down. To find the %error in your measurements you need to compare the values in columns D and F for regular chips, and the values in columns E and G for low/non fat chips. To do this type in cell H2 =([F2-D2]/F2)*100; the brackets is the absolute value of the subtraction and simply means that it will record the result of subtraction as a positive number even if it came out to be negative. Go to the lower right hand corner of cell H2 and drag down. Repeat the same procedure for low/non fat chips; type in cell I2 =([G2-E2]/G2)*100 and drag down. Now you need to calculate the average and standard deviations for columns B through E. In the sample table, go to Cell A6, type in Average= then enter, then go to cell A7 type in Std. Dev= and press enter. Then in the cell right below the last data point (cell B6 here) type in =average(B1:B5) and press enter. Go to the lower right corner of this cell and drag it to the right (to cell E) now you have all the average values for columns B through E. In cell B7 type =stdev(B2:B5) and press enter, then drag the lower right corner of the cell to the right (through cell E) now you have all the standard deviation values for cells B through E. At the end of the Excel spreadsheet show the formulas that you used in order to calculate each value: (Remember the names may be the same, but the formulas will need to be corrected to correspond to the values in your class. Also equations used for low/non fat chips must also be recorded)

Mass of Fat (reg) = (RawData!B2-RawData!A2)

Exp. % Fat (reg) = (B2/RawData!C2)*100

Theo. % Fat (reg) = (16/28.3)*100

% Error (reg) = ([F2-D2]/F2)*100

In all of your calculations watch for significant figures.

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