Laboratory Detective Work Performance Assessment

Laboratory Detective Work Performance Assessment

Students completed this performance assessment at the end of the matter unit. They worked in their teams of 4, one group at a time, while I observed and assessed them. This assessment is part of the new textbook program. I conducted the assessment using the textbook guidelines and made revisions for during and following carrying out the performance assessment. The example below is the original textbook version, and the rubric that goes with it.

Laboratory Detective Work: You will be given six containers with powders in them. Your challenge will be to identify these powders.

Procedure:

With your partners, carefully study the data in the chart below. Determine which properties you will be testing are physical properties and which are chemical. On a separate sheet of paper, make a list of the properties you will be testing.

Powder	How it looks	How it reacts with water	How it reacts with vinegar	How it reacts with iodine
Salt	Small white cubes	Dissolves, clear solution results	No reaction	No reaction
Sugar	White grains of assorted shapes	Dissolves, clear solution results	No reaction	No reaction
Powdered milk	Tiny white particles	Forms cloudy solution	No reaction	No reaction
Cornstarch	Tiny white particles	Milky-looking, does not all dissolve	No reaction	Turns dark blue
Baking soda	Small grains of assorted shapes	Dissolves, clear solution results	Forms bubbles	No reaction
Plaster of Paris	Tiny white particles	Forms cloudy, warm mixture that hardens	No reaction	No reaction

You and your partners will move from station to station, testing each powder to determine its properties. After each testing, record your data in the chart below.

Powder	How it looks	How it reacts with water	How it reacts with vinegar	How it reacts with Iodine
A
B
C
D
E
F

Results

As a team, analyze the data in both charts. Discuss what you have observed and be prepared to present you conclusions about the powder’s identities. Write on a separate sheet of paper the identity of each powder and a summary of how your observations helped you identify the powders. Indicate which tests best helped your team in doing its detective work and why.

Laboratory Detective work rubric:

Assessed Items	Points	What to look for
Performing the tests	3 2 1	The student performed the tests with care and accuracy and clearly recorded the results. The student performed the tests with care but was not accurate in recording the results. The student was careless in performing the tests and recording the results.
Completing the chart and identifying the powders	3 2 1	The student’s chart is complete, and powders are correctly identified. The chart listed properties of some of the powders, and those are correctly identified. Properties are inaccurately recorded, or identifications are not correct.
Written summary	3 2 1	The student provides details of the procedure and how conclusions were drawn and indicates an understanding of how careful observations result in accurate identification. The student clearly communicates his or her conclusions but gives little explanation for why they were drawn. The student leaves out many details or fails to show how conclusions were drawn.

Laboratory Detective Work Revised Performance Assessment

I made several revisions to this performance assessment prior to administering it. First, I revised some of the directions to make them more clear. For example, in the procedure section, I eliminated the "determine which properties are physical and chemical" requirement in order to save time. As it was, this assessment took almost 2 weeks to complete due to the time required for each group. Also, I wanted to avoid the need for extra papers, as students were busy working to identify the powders and record their data. Extra paper would have been extra materials to keep tract of. I also wanted to get students thinking about the differences in how each powder reacts with the substances. To do this, I added "determine some differences in how each material reacts with each substance" to the procedure directions.

I anticipated that students would have trouble and take extra time in making decisions about who gets to do what in this experiment. As my class has worked extensively on decision making skills, and cooperative learning skills, I wanted to use this assessment to apply their knowledge. For example, I gave all the teams 5 minutes prior to beginning the performance assessment to make a decision about how to proceed. For example, one team decided that they wanted to each (all 4 members) test out each powder. While this is ideal for saving time, they felt like they had the best chance for reducing errors if they all completed each powder mixing and then shared their thoughts at the end. Most teams, however, opted to split up the powders, so that 1-2 students worked on a powder at a time. The other group members then trusted that the student or students properly identified the powder. To facilitate this decision making process, I gave the directions orally and I added them in step 2 of the procedure.

To save time and space (as work space was crowded with powders, tools, etc.), I removed step 3 in the results section. In place of it, I added a column to the table, labeled, "conclusion", where students wrote the name of the powder they believed each to be.

Laboratory Detective Work: You will be given six containers with powders in them. Your challenge will be to identify these powders.

Procedure:

With your partners, carefully study the data in the chart below. Determine some differences in how each material reacts with each substance.

Powder	How it looks	How it reacts with water	How it reacts with vinegar	How it reacts with iodine
Salt	Small white cubes	Dissolves, clear solution results	No reaction	No reaction
Sugar	White grains of assorted shapes	Dissolves, clear solution results	No reaction	No reaction
Powdered milk	Tiny white particles	Forms cloudy solution	No reaction	No reaction
Cornstarch	Tiny white particles	Milky-looking, does not all dissolve	No reaction	Turns dark blue
Baking soda	Small grains of assorted shapes	Dissolves, clear solution results	Forms bubbles	No reaction
Plaster of Paris	Tiny white particles	Forms cloudy, warm mixture that hardens	No reaction	No reaction

Determine how you and your partners will test each powder. You many each test every powder, or you may divide up the powders. Make this decision first as a group. Next, record your data in the chart below.

Powder	How it looks	How it reacts with water	How it reacts with vinegar	How it reacts with Iodine	Conclusion
A
B
C
D
E
F

I revised the rubric significantly.

First, I removed the written summary component. I could not find directions in the textbook assessment for a written summary anywhere. Also, I noticed during the experiment, that many student had difficulty organizing themselves to follow the procedure. Some students seemed to "jump" from powder to powder and thus forgot which powder had reacted with which substance. Therefore, I added this component to the "performing the tests" section. I also noticed that several students correctly identified the powders but incorrectly wrote them in their charts. I added this to the "completing the chart and identifying powders" section. While students performed this assessment in teams, I graded them individually using the rubric. I also posted a copy of the revised rubric in the performance assessment area. I explained the directions orally and wrote them on chart paper that was posted in the area as well. All questions were answered prior to the start of the assessment. My role during the performance assessment was to observe and evaluate students. Most students acted like I wasn’t there, which allowed me to gain insight into how they perform tests, follow procedures, share materials, make conclusions, and work with their team. I also realized that by not posting written directions in the past, I have relied too heavily on student’s auditory comprehension. This resulted in my time being taken up answering questions, rather than on assessing student performance. There are two parts of this assessment that I plan to revise for next year. First, this assessment, while valuable, simply took too much time (nearly 2 weeks). IN order to remedy this, I plan to use the "portable teacher" strategy in which I move from team to team with supplies. I also plan to have 2 groups working on this at a time, rather than 1 group. The assessment takes each group so long, that running 2 groups at a time should still allow me ample time to assess each student. Another component that I’d like to revise involves the students. Next year, I plan to have students give themselves a score and each teammate a score for this experiment. In addition, I will expect students to write a 3-4 sentence explanation for their own score and their teammate’s scores. As I am trying to progress into using more student self-evaluations and reflections, this is the first step.

Laboratory Detective Work Revised Rubric

Assessed Items	Points	What to look for
Performing the tests	3 2 1	The student performed the tests with care and accuracy and clearly recorded the results. Student was organized in following the procedure. The student performed the tests with care but was not accurate in recording the results or was disorganized in conducting the experiment. The student was careless in performing the tests and recording the results, due to lack of organization in following procedure.
Completing the chart and identifying the powders	3 2 1	The student’s chart is complete, and powders are correctly identified. The chart listed properties of some of the powders, most of those are correctly identified or student properly identified the powder, but improperly filled in the table. Most properties are inaccurately recorded, and identifications are not correct.