# Making a Graph on Graph Paper

Time to make a graph?!? Follow these step-by-step instructions, and you are sure to have a graph that will impress even the grouchiest TA.

Step 1: When making a graph on graph paper, it is important to have graph paper with fine enough divisions to give you useful information from your graph. One acceptable type of graph paper is Purdue Form F, available at the bookstores. Not acceptable graph paper includes pages out of your lab notebook or quad-rule paper (4 squares per inch).

Step 2: After selecting a suitable piece of paper, grab a ruler. It is time to draw your axes. You will need a y-axis (up and down) and an x-axis (side to side). Typically, but not always, these will intersect in the lower left corner of your graph paper. Graphs are always Y vs. X. For example a graph of mass vs. volume would have mass on the y-axis and volume on the x-axis.

Take a look at your data. One set of data probably spans a much larger range than the other. You will want to orient your graph paper so that the larger data set will be plotted on the long side of the paper. (Do not be afraid to turn your paper sideways. Your TA is smart and will know which way to hold the graph while looking at it.) Now use that ruler to draw you axes. Don't forget to label them each with a name and proper units.

Step 5: Now that you have the data, you need to decide on a shape. The shape is never akindergarten connect-the-dots project. Most likely you need either a line or a curve. (Check your lab manual, it probably will tell you there in case the dots on your graph don't make it obvious). This line or curve does not need to touch every data point on the graph. It should be drawn to be smooth and come close to most of the points.

Step 6: Give your graph a title. No creativity required. A simple Mass vs. Volume type title will certainly sufice. You may want to include the section of the experiment, trial number, or other identifying information as a subtitle.

Step 7: Get whatever information you need from your graph.

Step 8: Check your graph against this list:

• Appropriate quality graph paper
• Graph fills the entire sheet of this high quality paper
• Axes are labeled (including units)
• Divisions on axes are evenly spaced.
• Your data plot is a smooth line or curve drawn to fit the pattern of your data
• Graph has a title that includes all important information
• You have extracted the information you need from the graph

In order to get the most accurate slope from a graph, you must first make sure your data is taking up at least 3/4 of the space on the page. After adding the data points to your graph, you will want to draw in either a straight line or a curve. For activity 3, you will use a straight line. This line will never be a connect-the-dots project. Rather, the goal is to get the line to come close to as many of the points as possible.

From this graph, we are trying to determine the density of an unknown substance. First, you know that density is mass divided by volume.

When you made your graph, you plotted volume on the x-axis and mass on the y-axis. The equation for determining the slope is

.

Thus you have mass divided by volume and the slope of the line is equal to the density.

Next you need to determine the slope of the line. Look at the line you have drawn and choose two places where the line you have drawn crosses a corner of one of the "boxes" on the graph paper. You do NOT want to use your original data points because that would defeat the purpose of drawing a straight line that fits the data! Take the coordinates of these two points and put the data into the slope equation to calculate the slope.

If you have followed all of these steps and made wise decisions along the way, you should now have a graph that is pleasing to the eye, chock full of information, and worth lots of points on your lab report.