# Thinking scientifically about graphing: a classroom exercise for general chemistry

## In-Class Activity

Submitted by Jennifer Look, Mercer UniversityThis excercise explains the basics of drawing graphs for an introductory chemistry class. It give examples of common pitfalls and how to avoid them. Students are guided through graphing a data set, adjusting axes, adding trend lines, modifying legends and adding appropriate labels. The excercise also provides several examples of graphs and asks students to critically evaluate them.

Attachment | Size |
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PC version of the worksheet | 389.92 KB |

Word versions can display graphs differently, pdf shows how they should look | 513.75 KB |

After completing this activity, students will understand basic requirements for scientific graphing. They will be able to interpret graphs, identify common mistakes, and use Excel 2010 (available in campus computer labs) efficiently to generate graphs. Student will gain experience critically analyzing graphs, and communicating about data interpretation.

Computer, Microsoft Excel 2010

Students typically work in groups of 3 -4 students. We do this exercise during the third week of our first semester General Chemistry class.

**Figure 1 ** You can put ANY data with an irregular axis here. The graph shown is based on the song “99 problems” which is rather vulgar and misogynistic. I use this because it gets students thinking about how *any* data, even JayZ lyrics, can be graphed. You don’t need an equation or explanation to look at a relationship. Some years I use a version of the pirate vs global temperature graph from “An Open Letter to the Kansas School Board”, other times I just put rainfall versus year (skipping some years).

**Selecting groups **I ask the students to line up in terms of how comfortable they are with computers. I give them two examples of "expert" Excel tasks - using a concatentate formula to combine data and using conditional formatting to change cells colors - and have people very comfortable with those tasks stand at one end of the room, and people who aren't sure how to turn a computer on at the other. Then I ask them to talk to each other and pick a group of people to work with. I explain that the goal is to get everyone to complete the activity within the 75 minute period, so the faster students need to help out the others and everyone needs to help each other stay focussed and on track.

**Timing**

- Group selection takes about 10 minutes, including logging on to computers.
- They have about 5 minutes for reading and brainstorming about section 1 (parts of a graph).
- Section 2 (graph types) takes the slower groups about 10 minutes.
- Section 3 (drawing a graph) is fast - only about 2 minutes.
- Section 4 (axes) is where some of the more proficient groups typically provide a lot of assistance to the others. This typically takes about another 10 - 15 minutes for all groups to complete.
- Section 5 (lines) takes about 5 minutes, except for groups that get into deep conversations about what is science, and the difference between laws and theories. I love those conversations, but this is an easy section to cut in the interest of time.
- Section 6 (labels) takes the remainder of the period. Groups submit their graphs as well as the answers to the worksheet questions.