Instructions: This assignment will require you to use Excel to make a series of
ID: 481890 • Letter: I
Question
Instructions: This assignment will require you to use Excel to make a series of graphs and answer related questions. Detailed instructions of how to use Excel for graphing are found in the lab manual, Appendix 4, starting on page 89. All graphs and answers to questions must be your own work. You may not work with other students for this assignment 1. An experimenter measured the volume occupied by a gas at a series of temperatures, gathering the data in the table below. Produce an appropriate graph to determine the relationship (if any between these two quantities Temperature (o Volume (mL 102 133 115 248 39 365 371 262 324 195 285 a. Enter the data into an Excel* spreadsheet in the appropriate columns. Think: Which is the independent variable and which the dependent variable? Over which variable did the experimenter have control? What was measured as a function of what?) Follow the procedure given in Appendix 4, Part B to produce a linear plot of this data set including a Trendline and R-squared value. Using the "Checklist for a Presentable Graph" in Appendix 4, Part C, format and print the graph. The graph title should be descriptive of the data, not the question number. b. Examine the points on the graph. Determine if they all appear to fit well on the Trendline. You might want to examine the R-squared value as well. Return to the data spreadsheet and delete any questionable point(s). (To do t the number of its row, right-click with the mouse, and left-click on "Delete.") Re-name the graph indicating which temperature date point(s) were removed. Re-format the graph if necessary and print the revised graph.Explanation / Answer
1 a) We need to choose temperature as the independent variable since the experimenter had control over the temperature. He can easily control the temperature using a temperature switch or a temperature program. Plot the data with the temperature as the horizontal axis and the volume as the vertical axis.
The plot is shown below. The trendline indicates that there exists a linear relationship between temperature and volume occupied by the gas.
b) The data doesn’t fit the graph perfectly. Infact, the R2 value is 0.7913. For a good linear fit, the R2 value should be atleast 0.98-0.99. Therefore, there are certainly outliners in the plot. In particular, the volume readings at -102C and 39C seem dubious. We can re-construct the graph after eliminating these two data points.
The plot looks much cleaner. The trendline is perfectly linear and the R2 value is almost close to 1.0, indicating that volume of an ideal gas and its temperature are indeed linearly related.
2 a) Plot the data by putting volume along the horizontal axis and mass along the vertical axis. Note that the experimenter had no control over either the mass or the volume of pieces and hence, neither is a dependent variable here.
The graph is plotted above. The graph is more or less linear. The R2 value is 0.958 indicating that there are outliners.
Remove the most questionable data point (the extreme outliner) and re-draw the graph.
The slope of the curve is 1.3482 g/mL. The R2 value is almost close to 1.0, indicating this is an extremely good fit.
It is not necessary to remove additional data points since we have already achieved a high R2 value.
b) The data set (27.735 g, 14.34 mL) was eliminated.
d) The slope of the line is known as the density. Density is defined as mass per unit volume of a substance and has the unit g/mL.
e) Use the linear equation; here y = mass = 10.700 g.
Plug this value of y in the linear equation and use the value of the slope as 1.9482 g/mL.
Therefore,
10.700 g = (1.3482 g/mL)*x – 0.3866 g (the intercept must have the same unit as y).
==> 1.3482x mL-1 = 10.3134
==> x = 7.6497 mL 7.65 mL (ans).