CHM 2045L Lab 2: Data Tables and Plotting Lab Data
Learn how to make a data table.
Learn how to plot lab data, including titles, labels, and best-fit straight line.
When making data tables, the following are required:
Title: A few words to briefly describe the type of information in the table. If more than 1 table is
present, number the tables. For example,
Table 1. Data for Lab 4: Determining the formula for a compound.
Table 2. Summary %Cu and %Cl in copper chloride compounds.
The 1st row of the table should be a header row and contain titles for each column. If there are units
associated with the values, include those in parentheses. When possible, try to not to have tables spread
over 1 page. For large tables this may not be avoidable, in which case make sure to include the header
row at the top of the table on each page.
Plotting Data (also known as Graphing Data):
When graphing scientific data, there are several things that must be included in addition to plotting the
data points, such as a title and axes labels including any applicable units. In this lab we will cover the
basics of what is required for graphs you will be making in this and subsequent chemistry labs.
When plotting data points, typically the 1st column is the value for the x-axis (horizontal axis) and the 2nd
column is the value for the y-axis (vertical axis). Some lab data may require they be switched so that the
slope of the best-fit data line gives a desired result. For example, plotting mass on a y-axis and volume on
an x-axis would result in a slope that gives the density of the substance.
Every graph or plot should have a title that clearly states what type of data is being shown. In axes
should also be labeled with what is being measured as well as the units used to measure. For example, an
axes may be labeled volume (in mL) or as volume, mL. Both ways are acceptable and are often used.
After data points are plotted, it’s often necessary to find the best-fit straight line. This should be a
straight line that is drawn as close to the points as possible and usually doesn’t not include all of the data
points. Figure 1 shows an example of a best-fit straight line.
Figure 1. Sample best-fit straight line.
Equation for a best-fit line: A line has the equation:
y = vertical axis value (also known as the ordinate)
x = horizontal axis value (also known as the abscissa).
m = slope, which may be found using x and y values from 2 places on the best-fit straight line.
Ideally these 2 places on the line should not be close together. Slope = (y2-y1)/(x2-x1). The
units of the slope depend on the units of the y- and x-axes.
b = y-intercept (the value of y where x=0).
0 50 100 150
Pressure (mm Hg)
Sample Data Plot
Procedure: For each of the following sections, follow the directions to graph the data. The graphs and
answered questions will count as your lab report for this lab. Each student must turn in their own graphs
and answers to the questions. You must do the graph for #1 by hand using graph paper, a ruler, and
calculator. For #2 and #3 you may either do them by hand or using a spreadsheet like Excel, but you
must print out your spreadsheets as well as your graphs.
1. Given the following data from a gas experiment measuring changes in volume in response to
increasing the temperature:
Data for #1.
Temperature (oC) Volume (L)
a. Plot the points on a graph.
b. Draw a best-fit straight line.
c. Calculate the slope.
d. Calculate the y-intercept.
e. At what temperature would the volume = 1.50L?
f. At what volume would the temperature = 125.0 oC?
g. What is the equation for the line?
2. Given the following data, graph mass vs. volume so the slope will give the density of the
Data for #2.
Volume (mL) Mass (g)
a. What would the volume be at 25.0g?
b. Draw the best-fit straight line and write the equation for the line on the graph.
c. What is the slope of the graph?
d. Using the table at the end of this lab to identify the metal.
3. Given the following non-linear data, plot pressure along the y-axis and 1/volume along the x-axis.
Data for #3.
Volume (mL) Pressure (torr)
a. Draw the best-fit straight line.
b. Write the equation for best-fit straight line.
c. What is the slope of the line?
Table of metallic densities for #2.