Study Guide

Field 104: Chemistry 
Sample Constructed-Response Assignment

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Test Directions for the Constructed-Response Assignment

This section of the test consists of one constructed-response assignment. You will be asked to prepare a written response of approximately 300to600 words on the assigned topic.

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

  1. typed into the on-screen response box,
  2. written on a response sheet and scanned using the scanner provided at your workstation, or
  3. 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.

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

As a whole, your response must demonstrate an understanding of the knowledge and skills of the field. In your response to the assignment, you are expected to demonstrate the depth of your understanding of the content area through your ability to apply your knowledge and skills rather than by merely reciting factual information.

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

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

The constructed-response assignment is intended to assess subject matter knowledge and skills, not writing ability. However, your response must be communicated clearly enough to permit valid judgment of the scoring criteria. Your response should be written for an audience of educators in this field. The final version of your response should conform to the conventions of edited American English. Your response must 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 topic. Remember to review your work and make any changes you think will improve your response.

Any time spent responding to the 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  start uppercase NOT end uppercase  be scored.

Sample Constructed-Response Assignment

Competency 0012 
Analyze a lesson plan and student work sample for a laboratory investigation related to a performance expectation in the Oklahoma Academic Standards for Science, then describe differentiated strategies that address student needs.

 start bold Use the information provided in the exhibits to complete the assignment that follows. end bold 

Using your knowledge of standards-based learning goals and scientific investigations, prepare a response of 300to600 words in which you:

Be sure to utilize  start bold all end bold  of the exhibits in your response.

Exhibit 1: Class Content

In a high school chemistry class, students have been learning about how knowing the identity of reactants in a chemical reaction allows products to be predicted and the reaction to be characterized. They have learned basic reaction types and how to represent chemical compounds with formulas, and reactions with equations. They are also familiar with laboratory techniques for accurate measurement and safe conduct. Students will work in pairs to observe the production of precipitates of halide salts and silver nitrate, the displacement of halide ions in solution due to reaction with molecular halogens, and the creation of solutions of molecular halogens and an organic solvent. All observations are qualitative. Students will use their results to reason about patterns of chemical properties.

Exhibit 2: Lesson Plan

The following is an excerpt from a high school chemistry lesson plan.

Unit Subject: Chemical Bonding

Subject of the Lesson: Reactions of Halogens and Halides

Student Content Standard: CH.PS1.2 Construct and revise an explanation for the outcome of a simple chemical reaction based on the outermost electron states of atoms, trends in the periodic table, knowledge of the patterns of chemical properties, and formation of compounds.

Lesson Objective:

Materials:

Procedure:

Assessment: Students will be assessed based on their chemical equations and written explanations of their observations.

Exhibit 3: Student Data

Part 1: Reaction of Halide Salts with Molecular Halogens

Table depicting the results of a chemical reaction
blank Chlorine Bromine Iodine
Potassium Chloride Greenish solution, color of the chlorine water, no reaction seen Yellow-brown solution, color of the bromine water, no reaction seen Brown solution, color of the iodine water, no reaction seen
Potassium Bromide Solution turned yellow, color change reaction Yellow-brown solution, color of the bromine water, no reaction seen Brown solution, color of the iodine water, no reaction seen
Potassium Iodide Solution turned brown, color change reaction Solution turned brown, color change reaction Brown solution, color of the iodine water, no reaction seen

Part 2: Reaction of Halide Salts with Molecular Halogens, with Organic Solvent*

*Note the color of the solvent layer floating on top of the solution.

Table depicting the results of a chemical reaction involving an organic solution
blank Chlorine Bromine Iodine
No Salt Added slight yellow green brownish-yellow purple
Potassium Chloride slight yellow green brownish-yellow purple
Potassium Bromide yellow yellow purple
Potassium Iodide purple purple purple

Part 3: Addition of Silver Nitrate Solution

Table depicting the results of adding silver nitrate to a chemical solution
Potassium Chloride A white precipitate is produced, instantly, dissolves in ammonia.
Potassium Bromide A creamy-colored precipitate is produced, dissolves over time in enough concentrated ammonia.
Potassium Iodide A yellowish precipitate is produced, doesn't dissolve in ammonia.

Exhibit 4: Student Analysis

1. We did not observe two of the halogens. Predict what F and At would have behaved like in these reactions.

Potassium fluoride would probably react with all the halogens except its own halogen, fluorine. This is because it's the top element in its group on the periodic table. It's a small atom with a low atomic number, so it shouldn't be hard to knock out of a reaction.

Astatine fluoride would probably react with none of the halogen. The reason is the opposite of fluorine. It's a very large atom, with atomic number 85.

2. Write a chemical equation for one of the reactions in Part 1. Explain the change that happened.

 2 aqueous K B R plus aqueous C L 2 produces 2 aqueous C L plus aqueous B R 2 

The chlorine atoms replaced the bromide ions in solution. Actually the KBr is in the form of free-floating ions, so it's more like the chlorine atoms took an electron each from the bromides, turning the bromides into their molecular bromine form.

3. Write a chemical equation for one of the reactions in Part 3. Explain the change that happened.

 aqueous K I plus aqueous A G N O three produces two solid K A G plus solid I N O three 

The two compounds are free-floating ions, and there was a double replacement that occurred. Atoms and polyatomic ions swapped into new pairings. The two solids made are the yellow precipitate we observed, mixed together.

4. Why did some of the same reactions show a different color in Part 2? What was the role of the organic solvent?

The solvent sort of focused the color of the halogen (chlorine, bromine, or iodine) so it could be more easily seen. The molecules of the halogens are linear, nonpolar molecules, and a lot of organic solvents are nonpolar too, unlike water. The halogen can dissolve in the mineral oil.

5. Use your knowledge of atomic models to explain the patterns you saw in this investigation.

So, halogens all have seven valence electrons, which makes their reactivities similar, so they can react with the same stuff, like the silver nitrate. They are different elements, with different numbers of protons, neutrons, and electrons, though, so when they react with each other, one can come out on top. I think the bigger atoms don't like to be kicked out of their molecules by other halogens, but smaller atoms can't do much about it.

Sample Strong Response to the Constructed-Response Assignment

 start bold Please note: The sample response provided below is for review purposes only and should not be used in a response on an operational exam. Use of the exact words and phrases presented in this sample response will result in a score of "U" (Unscorable) due to lack of original work. end bold 

The goals of the lesson align with the Student Content Standard (CH.PS1.2) from exhibit 3 in two specific ways: 1. Students predict the outcome of a reaction based on the valence electron configurations of the reactants and their placement on the periodic table; and 2. Students use lab results to verify their predictions and extrapolate other potential reactions using other members of the same chemical families.

Safety in the lab is of utmost importance. Students must wear PPE (protective clothing like a lab coat, gloves, goggles, and possibly masks if listed in the safety forms). Long hair should be tied back. The teacher must ensure that students know the location and use of safety equipment, especially the shower, eyewash, vent hoods, spill kit, and escape routes. Chemicals should be stored correctly (contained separate storage units for different classes of hazards) and waste containers should have secondary containment. All chemicals must be labeled correctly. Lastly, students should never work unsupervised in the lab.

Strengths of the student work sample (Exhibit 5) include a well-organized data sheet with detailed observations and notations. The student correctly identifies halides as having 7 of the 8 needed valence electrons for a full valence shell and therefore would react similarly (their prediction of what would happen with the 2 other halides not tested in the lab). The student also identified smaller atoms as the most reactive (question 5). The student understands the concepts of single and double displacement reactions (questions 2 and 3). The student recognizes that the halides are linear and non-polar (question 4). Using that information, the student predicted that those halogens would be soluble in mineral oil.

The student work sample also shows some weaknesses in understanding. While the student understands the concepts of single and double displacement reactions, they erroneously recombine the products, trying to bond the cations together and the anions together in problem 3, and fail to include the potassium in the products in problem 2. In question 1, the student states fluoride salts would react with other halogens. Since fluorine is more reactive than other halides, there would not be a reaction (question 1). In the last question, the student mistakenly states that larger atoms would not be displaced by smaller atoms. Smaller atoms are more reactive and would displace larger atoms in a molecule.

The teacher should use differentiated instructional strategies to build on the student's strengths in order to address the student's needs. Some of these strategies would include:

1. Providing the student more opportunities to practice. Students should have more practice predicting outcomes of displacement reactions. Students could pair-share their work, or the teacher could have students resolve the problems on the front board.

2. Students could research various aspects of the halides (structure, activity, etc.) and jigsaw their findings to the class.

3. Students could do a post-lab assignment or quiz and then further investigate (online for example) any portions of the assignment that they do not understand.

Future instruction could involve:

1. Later labs in which reactions and outcomes need to be predicted. These might include labs involving solubility, limiting reagents, electrochemistry, titrations, and other atomic families. Errors in product formation could be problematic.

2. These skills could be used in labs like electroplating as well as predicting outcomes such as pH, changes in solubility, and extraction of contaminants from a solution.

Rationale for the Sample Strong Response

Please note that the response is evaluated based upon the four performance characteristics of Purpose, Subject Matter Knowledge, Support, and Rationale. Please also note how the score point descriptions are based upon how the examinee attends to the performance characteristics. You should be very familiar with the CEOE performance characteristics and score scale and refer to them when reviewing this rationale.

This response generally achieves the purpose of the assignment. The response addresses all of the bullet points and includes details and specific examples demonstrating the candidate's understanding. The response indicates a general level of subject matter knowledge by the candidate, including a significant amount of relevant supporting evidence. The safety paragraph is adequate and uses several specific examples to demonstrate the writer fully understands safety concerns within a Chemistry classroom. The strengths and weaknesses are well thought out and include specific examples from the work (citing specific entries from the sample work – exhibit 5). The candidate provides three different related activities that are student-based, not just reteaching or reviewing materials to address the fourth charge of the prompt. The three examples would increase student understanding and would make it easier for students to expand their understanding with additional concepts from future lab activities. Overall, the response demonstrates a generally adequate understanding of Chemistry.

Sample Weak Response to the Constructed-Response Assignment

The standards are met because the student was able to predict patterns in reactions from similar elements. Strengths include accurate observations of the results and the ability to predict the results from similar types of elements. The student work indicates a chemical reaction by color changes. Although a weakness includes the lack of specificity in the results. While color changes are an indication that a reaction occurred, there is no recognition of a quantitative change. Color is a qualitative condition and as such cannot be measured directly. Perhaps an improvement would be the use of a spectrophotometer to measure the amount of light absorbed in a sample. That would provide measurable, quantitative analysis, what science needs as results. Another concern is that the work sample shows an error in the reactions. All of these materials are soluble and therefore, in solution are not linked together. So, the aqueous K C L should be written as aqueous K plus and aqueous C L minus. The solids in the next question are written correctly. Safety is important. Students should read the safety procedures posted in the lab and sign waivers indicating they understand lab safety.

To improve student understanding, I would recommend several homework assignments. One type would be worksheets that allow students to differentiate between qualitative and quantitative information. Another type is another worksheet reviewing solubility rules and problems. The teacher should adjust their lecture to address these issues, either by revising their presentation or taking more time to cover the topic. A post-lab quiz would demonstrate understanding and where deficiencies in understanding exist. Having the students do more problems would let them discover their errors and correct them. This would benefit the student not only in chemistry but in all their classes. Once they have determined their errors, re-presenting the lecture material will let the students learn the correct method.

Rationale for the Sample Weak Response

Please note that the response is evaluated based upon the four performance characteristics of Purpose, Subject Matter Knowledge, Support, and Rationale. Please also note how the score point descriptions are based upon how the writer attends to each of the performance characteristics. You should be very familiar with the CEOE performance characteristics and score scale and refer to them when reviewing this rationale.

Overall, this response partially fulfills the purpose of the assignment. While it does include a statement attempting to connect the assignment to the standards, the connection is very limited in scope. There is limited evidence of subject matter knowledge with several inaccuracies: Color change is an accepted indication of a reaction in chemistry, and quantification is not needed. Also, while it is true that ionic materials in solution do exist as ions, they are indicated as molecules, so the KCl in the student work is the correct notation. While the solids in question 3 do use the correct notation, the candidate did not recognize that the combinations were wrong. The student work mistakenly linked the cations and anions (the candidate did not see this significant error). Doing more worksheets without correcting the misunderstanding just reinforces the misconception. Reteaching is not an effective remediation tactic and is not student focused. Students would be more likely to succeed with a different approach to the material to correct the misunderstandings. Thus, the response provides only a partially accurate understanding of Chemistry.

Performance Characteristics

The following characteristics guide the scoring of responses to the constructed-response assignment.

Characteristics that guide the scoring of responses
Purpose The extent to which the response achieves the purpose of the assignment
Subject Matter Knowledge The accuracy and appropriateness in the application of subject matter knowledge
Support The quality and relevance of supporting details
Rationale The soundness of argument and degree of understanding of the subject matter

Scoring Scale

Scores will be assigned to each response to the constructed-response assignment according to the following scoring scale.

Score Scale with description for each score point.
Score Point Score Point Description
4  start bold The "4" response reflects a thorough knowledge and understanding of the subject matter. end bold 
  • The purpose of the assignment is fully achieved.
  • There is a 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  start bold The "3" response reflects a general knowledge and understanding of the subject matter. end bold 
  • The purpose of the assignment is largely achieved.
  • There is a generally accurate and appropriate application of subject matter knowledge.
  • The supporting evidence generally supports the discussion; there are some relevant examples.
  • The response reflects a general understanding of the topic.
2  start bold The "2" response reflects a partial knowledge and understanding of the subject matter. end bold 
  • 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  start bold The "1" response reflects little or no knowledge and understanding of the subject matter. end bold 
  • 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 unscorable because it is illegible, not written to the assigned topic, written in a language other than English, or lacking a sufficient amount of original work to score.
B There is no response to the assignment.