Graphing Rules: the Following Are a Few Guidelines to Help You in Graphing Your Data. Please

Graphing Data

Graphing Rules: The following are a few guidelines to help you in graphing your data. Please use this list for reference. Put this in the lab section of your notebook.

1. What are you graphing? By convention, the independent variable goes on the x-axis. The independent variable is the one that you control in your experiment. The dependent variable is the one that you measure. Sometimes it may be unclear which is which, but most often it will not.

2. What scale do you need? Do either of your axes need to go to zero? Think about what information you need from your graph. Many times you do not need to go to zero. Use as much of the page as possible. If your data goes from values from 50-75 on the x-axis, don't number your axis from 0 to 250. Choose a convenient scale. A graph is easier to read and/or plot when each square represents a value of 1, 2, 5, or a multiple of ten times these numbers: 10, 20, 50, or 0.2, 0.5.

3. Indicate the units used; examples: temperature (oC), mass (g), distance (cm)

4. Label your axes. What did you measure and what are the units?

5. Plot data points carefully. Circle or box the points.

6. Draw the "best fit" line (or curve when appropriate. Do not "connect-the-dots";. Your line may not go through some of the data points. Sometimes it may not go through any. Drawing the best fit line means splitting the difference between higher and lower values - leaving about the same number of points above and below the line.

Always use a straight edge. A clear ruler works great.

Give your graph a title. Usually "y versus x for ______" is appropriate. An example is, "Volume vs. Temperature for the warming of 1.0 g water at 101.3 kPa". Graphing exercise: Using the following data create a line graph for each set of data. This is a very simple exercise. All you have to do is follow directions and enter the information as asked for. The program will then create the graphs for you. Put your laptop number at the end of your graph title.

Temperature change over Time for Volume of a gas over time for a particular phase changes in water: gas:

Temperature Time Temperature Volume (oC) (min) (oC) (mL)

-20 0 25 100.0 -10 1 30 101.7 0 2 35 103.4 0 15 40 105.5 0 16 45 106.7 0 17 50 108.4 0 18 55 110.1 5 19 60 111.7 15 20 65 113.4 40 25 70 115.1 65 30 100 38 100 39 100 100 100 146

Vapor pressure of water over Temperature:

Temperature Pressure (oC) (kPa)

0 0.61 5 0.87 10 1.23 15 1.71 16 1.81 17 1.93 18 2.07 19 2.20 20 2.33 21 2.49 30 4.24 40 7.37 50 12.3 80 47.33 100 101.3 Exercise Review Questions

1. What is a line graph best used to show?

2. What is a bar graph best used show?

3. What is circle graph best used to show?

4. Define the following terms:

a. dependent variable b. independent variable

5. State one similarity between a bar graph and a circle graph.

6. State one difference between a bar graph and a circle graph.