National Evaluation Series™ Profile: Chemistry (821)

Content Domain VI: Integration of Knowledge and Understanding

Competencies:

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0017 Prepare an organized, developed analysis of a key topic in chemistry related to Matter and Its Interactions: Periodic Properties or Motion and Stability: Forces and Interactions.

Descriptive Statements:

Describe the key scientific concepts that relate to a given topic.
Use representative graphs, formulas, and/or diagrams with proper labels to model the presented topic.
Discuss how a specific science and engineering practice (e.g., developing and using models, constructing explanations, designing solutions) could be used to help a group of students understand phenomena related to the given topic.

0018 Prepare an organized, developed analysis of a key topic in chemistry related to Matter and Its Interactions: Chemical Structure and Reactions; Matter and Its Interactions: Substances, Mixtures, and Solutions; or Energy in Chemical Systems that emphasizes the application of science and engineering practices in a classroom setting.

Descriptive Statements:

Form a testable scientific claim that addresses a given topic.
Outline a specific scientific procedure to investigate the proposed claim, including identifying variables and controls.
Describe any appropriate safety considerations and practices for this procedure.
Describe a possible result provided by collected data and provide reasoning of how the collected data provide evidence that supports or refutes the tested claim.
Discuss how a specific science and engineering practice (e.g., developing and using models, planning and carrying out investigations) could be used to help a group of students make sense of phenomena related to the given topic.

Sample Open-Response Item Assignment

The following materials contain:

Sample test directions for the open-response item
A sample open-response item
An example of a strong response to the open-response item
The scoring rubric

Sample Test Directions for Open-Response Items

This section of the test consists of two open-response item assignments. You will be asked to prepare a written response of approximately 150 to 300 words, or 1 to 2 pages, for each assignment.

Read the assignments carefully before you begin your responses. Think about how you will organize your responses. You may use the erasable sheet(s) to make notes, write an outline, or otherwise prepare your responses. However, your final response to each assignment must be either:

typed into the on-screen response box,
written on a response sheet and scanned using the scanner provided at your workstation, or
provided using both the on-screen response box (for typed text) and a response sheet (for calculations or drawings) that you will scan using the scanner provided at your workstation.

Instructions for scanning your response sheet(s) are available by clicking the "Scanning Help" button at the top of the screen.

As a whole, your response to each assignment must demonstrate an understanding of the knowledge of the field. In your response to each assignment, you are expected to demonstrate the depth of your understanding of the subject area by applying your knowledge rather than by merely reciting factual information.

Your responses to the assignments will be evaluated based on the following criteria.

PURPOSE: the extent to which the response achieves the purpose of the assignment
SUBJECT KNOWLEDGE: appropriateness and accuracy in the application of subject knowledge
SUPPORT: quality and relevance of supporting evidence
RATIONALE: soundness of argument and degree of understanding of the subject area

The open-response item assignments are intended to assess subject knowledge. Your responses must be communicated clearly enough to permit valid judgment of the evaluation criteria by scorers. Your responses should be written for an audience of educators in this field. The final version of each response should conform to the conventions of edited American English.

Your responses should be your original work, written in your own words, and not copied or paraphrased from some other work.

Be sure to write about the assigned topics. Remember to review your work and make any changes you think will improve your responses.

Any time spent responding to an assignment, including scanning the response sheet(s), is part of your testing time. Monitor your time carefully. When your testing time expires, a pop-up message will appear on-screen indicating the conclusion of your test session. Only response sheets that are scanned before you end your test or before time has expired will be scored. Any response sheet that is not scanned before testing ends will NOT be scored.

Sample Item:

Use the information below to complete the exercise that follows.

Batteries are an example of a device that is powered by oxidation-reduction reactions. A battery can be produced using lead and lead (4) oxide. Half-reactions for this oxidation-reduction reaction are shown. The half-reactions can be used to predict which species will act as the anode and which will act as the cathode. The total amount of charge transferred can be predicted based on the amount of product formed.

Oxidation half-reaction:
P B open parens lowercase s close parens plus S O sub 4 sup 2 minus open parens lowercase A Q close parens yields P B S O sub 4 open parens lowercase s close parens plus 2 E sup minus, then delta E naught equals 0 point 3 5 6 volts

Reduction half-reaction:
P B O sub 2 open parens lowercase s close parens plus 4 H sup plus open parens lowercase A Q close parens plus 2 E sup minus plus S O sub 4 sup 2 minus open parens lowercase A Q close parens yields P B S O sub 4 open parens lowercase s close parens plus 2 H sub 2 O open parens lowercase L close parens, then delta E naught equals 1 point 6 9 volts

Use your knowledge of chemistry to write a response of approximately 150 to 300 words, or 1 to 2 pages, in which you:

form and describe a testable scientific claim that addresses how oxidation-reduction half-reactions and the amount of product can predict the anode, cathode, and charge transferred in a lead/lead (4) oxide battery;
describe a scientific investigation to test the proposed claim, including identifying variables, data to be collected, and any general lab safety considerations;
explain how the collected data may provide evidence that supports or refutes the tested claim; and
discuss how a chemistry teacher could use the science and engineering practice of "planning and carrying out investigations" to help students make sense of how oxidation-reduction half-reactions and the amount of product can predict the anode, cathode, and charge transferred in a lead/lead (4) oxide battery.

Sample Strong Response to the Open-Response Item

Sample Strong Response (Show Sample Strong ResponseHide Sample Strong Response)

A lead acid battery is a galvanic cell used as a reliable source of power for starting automobiles. Batteries are powered by oxidation-reduction reactions in which a transfer of electrons occurs. In this case the lead electrode acts as the anode. The half reaction shows the loss of electrons from lead. The lead oxide electrode is the cathode because it's gaining electrons. Oxidation is occurring on the lead (anode) and reduction is occurring on the lead oxide (cathode). Electrons are being transferred from lead to lead (IV) oxide. (See reactions.)

A number of lead-lead (IV) oxide cells could be created in the lab. Safety precautions would involve protection from contact with hazardous materials and contamination of the electrodes. Safe handling of the electrolyte solution would be necessary as it would be a weak sulfuric acid solution. The two electrodes would be suspended in the sulfuric acid solution and connected by a wire. As the reaction proceeds, a voltmeter would be attached to the wire and measure the electric potential of the cell, which should be about 2.05V.

You could then hook a number of cells together in series and measure the potential across multiple cells. The teacher could prompt the students to determine whether the number of cells or sizes of the electrodes will affect the electric potential. Students would conclude that the potential of an electrochemical cell is dependent on the half reactions at each electrode. To increase the output of a battery, it would be necessary to increase the number of cells. A car battery is based on this premise and is usually a 12V battery. Students would then understand that a 12V battery is simply the combination of 6 cells contained in a compartment.

Anode reaction, Solid P B plus aqueous H S O four negative one yields solid P B S O four plus aqueous H positive one plus two E negative one, E naught equals zero point three five six volts.

Cathode reaction: Solid P B O two plus three aqueous H positive one plus aqueous H S O four negative one plus two E negative one yields solid P B S O four plus 2 liquid H two O, E naught equals one point six nine volts.

Overall reaction: Solid P B plus solid P B O two plus two aqueous H S O four negative one yields two solid P B S O four plus two liquid H two O, E naught equals two point zero four six volts.

Scoring Rubric

Performance Characteristics

The following characteristics guide the scoring of responses to the open-response item(s).

Purpose	The extent to which the response achieves the purpose of the assignment.
Subject Matter Knowledge	Accuracy and appropriateness in the application of subject matter knowledge.
Support	Quality and relevance of supporting details.
Rationale	Soundness of argument and degree of understanding of the subject matter.

Scoring Scale

The scoring scale below, which is related to the performance characteristics for the tests, is used by scorers in assigning scores to responses to the open-response item(s).

Score Point	Score Point Description
4	The "4" response reflects a thorough knowledge and understanding of the subject matter. The purpose of the assignment is fully achieved. There is substantial, accurate, and appropriate application of subject matter knowledge. The supporting evidence is sound; there are high-quality, relevant examples. The response reflects an ably reasoned, comprehensive understanding of the topic.
3	The "3" response reflects an adequate knowledge and understanding of the subject matter. The purpose of the assignment is largely achieved. There is a generally accurate and appropriate application of subject matter knowledge. The supporting evidence is adequate; there are some acceptable, relevant examples. The response reflects an adequately reasoned understanding of the topic.
2	The "2" response reflects a limited knowledge and understanding of the subject matter. The purpose of the assignment is partially achieved. There is a limited, possibly inaccurate or inappropriate, application of subject matter knowledge. The supporting evidence is limited; there are few relevant examples. The response reflects a limited, poorly reasoned understanding of the topic.
1	The "1" response reflects a weak knowledge and understanding of the subject matter. The purpose of the assignment is not achieved. There is little or no appropriate or accurate application of subject matter knowledge. The supporting evidence, if present, is weak; there are few or no relevant examples. The response reflects little or no reasoning about or understanding of the topic.
U	The response is unrelated to the assigned topic, illegible, primarily in a language other than English, not of sufficient length to score, or merely a repetition of the assignment.
B	There is no response to the assignment.

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