Case-Based Questions

Prepared by Mark A. Templin, University of Toledo

CASE 4

You are excited about accepting a position teaching eighth grade science and beginning your first year of teaching. The first unit of the eighth grade science "scope and sequence" (i.e., your local school district's curriculum outline that specifies the depth and order of instructional topics to be taught) is "Matter and Its Changes." Essentially, this unit focuses students on understanding physical and chemical change and associated ideas. Thus, the unit focuses on helping students understand that when a chemical change occurs, new substances with new properties form. In contrast, when physical change occurs, substances change state (e.g., solid to liquid), but they do not change other properties (e.g., reactivity with other substances).

You decide to begin this unit by doing the "burning steel wool" activity (see page 40 of your text). Students will work in pairs. Each group will be given one-half a pad of "0000" steel wool and a piece of aluminum foil to use to construct a containing tray to hold the steel wool while it burns. Each student will "fluff" the steel wool, place it in the tray they made previously, and find the mass of the tray and steel wool sample.

You have one triple beam balance, but you have twelve "elementary style" single beam balances and several sets of "centi-gram" cubes. Because you have enough of the elementary style balances for two pairs to share one balance, you decide to use them instead of the triple beam balance. This decision, you believe, will help students work more efficiently and save instruction time.

On the day of the activity, you briefly demonstrate the procedure for finding the mass of the sample. When the class performs the activity, each group finds the mass of their sample. Each student then records the initial mass in his or her journal. Each group then burns their sample, lets it cool, and then finds the mass of the sample again. Once again, each student records the mass of the sample in his or her journal.

After all the groups are finished with these procedures, you have the class display their data by having one member of each group record their initial and final mass readings on a blank data table that you have drawn on transparency film.

You can hardly wait to turn on the overhead projector and reveal to the class the overall pattern in these data-that the mass of the sample increased after the sample burned. You realize that this will be a "discrepant event" for students, since most of them believe that substances get lighter when they burn. To your utter surprise, when the overhead projector is turned on, the data reveal that for six groups the mass increased, for three groups it stayed the same, and for five groups the mass decreased!

These events lead to the following questions.

1		What, if anything, went wrong with this activity? (Chapter Learning Performance 4.3, 4.4)
2		What should your next activity be? (Use the investigation web on page 119 of your text to help you) (Chapter Learning Performance 4.2, 4.3)
3		As described in the case, how valuable was the activity for students? (Chapter Learning Performance 4.1, 4.5)
4		How "real" was the science in the activity described in the case? (Chapter Learning Performance 4.5)
5		Compare and contrast the activity as it is described in the case to the same activity when it yields the expected results in terms of how it fits the nature of science. (Chapter Learning Performance 4.2)
6		Do you tell the class what the expected results were? Describe your role in helping the students make sense of these data. (Chapter Learning Performance 4.4)
7		Evaluate how worthwhile it would be to have students draw conclusions from the experiment presented in the case? In other words, should students be required to journal what they found out for homework that evening, regardless of how the mass of their group's sample changed? (Chapter Learning Performance 4.2)
8		Design a plan for a three activity sequence that will begin to help students make sense of the class's data. (Chapter Learning Performance 4.3)
9		Give three examples of questions you would ask students to help them make sense of the activity presented in the case. (Use pages 125-126 and Table 4.1 to help you.) What type of question is each your examples? (Chapter Learning Performance 4.5)
10		Based upon what happened with the case activity, you begin to believe that this unit could take longer than you thought because you now have two issues that confront you. First, you need to work with the class to "tighten up" procedures so they begin to get reliable data. Second, you will still need to work with the class to help them understand why steel wool gains mass when it burns. Is it worthwhile to spend the time it will take to help the students resolve both of these issues for themselves, or should you just tell them the answer and move on to the next planned activity? Explain your reasoning. (Chapter Learning Performance 4.5)