Study Guide

Field 013: Physical Science 
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  300 to 600  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

 start bold Read the information below; then complete the exercise that follows. end bold 

A lit candle, with a molecular formula of C sub 25 H sub 52, is placed upright in a pan of water, and a glass jar is inverted and placed over the candle. The mouth of the jar is submerged in the water, as shown in the diagram below.

The diagram shows the dish of water with the jar standing upside down in the center of the dish and a burning candle inside the jar.

The water level in the jar rises, the candle's flame goes out, and the water rises further. An observer suggests that the water rises because oxygen is being consumed, which creates a partial vacuum. A second observer points out that this explanation violates the law of conservation of matter since the system is closed.

Using your knowledge of science, write an essay in which you explain the behavior of this system in terms of scientific laws and concepts. In your essay:

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 second observer's conclusion is more accurate, because matter can neither be created nor destroyed. Also, the water acts as a seal, creating a closed system inside the jar. Because it is a closed system, matter cannot enter or leave the system. The first observer's conclusion is partially correct if one considers that the oxygen being “consumed” during combustion is molecular oxygen ( O sub 2 ) rather than atomic oxygen. However, the first observer has failed to take into account the fact that a chemical change has occurred, and the oxygen atoms have been incorporated into water and carbon dioxide molecules. Since the system is closed, there is no net loss of oxygen atoms from the system.

The balanced chemical equation for the burning candle is:

C sub 25 H sub 52 plus 38 O sub 2 produces 26 H sub 2 O plus 25 C O sub 2

If one assumes that the  O sub 2  and  C O sub 2  are in a gaseous state, the  C sub 25 H sub 52  is in a solid state, and the  H sub 2 O  is in a liquid state, then the gas laws would pertain to the  O sub 2  and  C O sub 2  only. According to Avogadro's law, the volume of a gas is directly proportional to the number of moles of the gas present (at constant pressure and temperature). Also, one mole of any ideal gas, regardless of its identity or chemical structure, occupies the same volume at a given temperature and pressure. The balanced chemical equation for the combustion of the candle indicates that there are more moles of  O sub 2  than there are of  C O sub 2  so according to Avogadro’s law, there would be a smaller volume of gas at the conclusion of the reaction than there was in the system initially.

The rise in the water level can be explained by looking at the conditions in the system when the jar is first inverted over the candle and after the flame burns out. Initially when the jar is inverted over the burning candle, the air pressure inside the jar equals the atmospheric pressure, so the water level is even inside and outside the jar. As  O sub 2  reacts and  C O sub 2  is produced, the volume of gas in the jar decreases. However, because the jar is rigid, the actual volume of space occupied by the gas does not change. This results in fewer gas molecules occupying the same volume of space, and so the pressure inside the jar drops. The pressure exerted by the air on the water outside the jar does not change though. Essentially, the atmospheric pressure pushes down on the water outside the jar and pushes the water up into the jar where the pressure is less. The gas laws state that the pressure exerted by a gas is inversely proportional to its volume, so as the water rises in the jar, there is less space available for the gas molecules and the pressure increases. When the water stops rising in the jar, equilibrium has been reached. That is, the pressure inside the jar pushing down on the water plus the weight of the water equals the force pushing down on the water outside the jar.

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.

The response fulfills the purpose of the assignment (refer to the instructions for the assignment) by providing a thorough response to all four bullets of the prompt. The writer has demonstrated an appropriate evaluation of each observer's conclusions about the system; the observers' conclusions have been correctly explained, as it was stated that a closed system will have no net loss of oxygen since no matter can enter or leave the system as described. The writer has given the correctly balanced chemical equation for the burning candle. Moreover, the response demonstrates sound reasoning, as the writer has given a proper explanation of Avogadro's Law and its appropriate application to explain how the system behaved by noting that the number of moles of  C O sub 2  in the final state is less than that of the moles of  O sub 2  in the initial state. The explanation then points out that since there are fewer  C O sub 2  gas molecules (25) than the original  38 O sub 2  molecules, the pressure in the jar at the end must be lower, thus allowing the water to rise. The latter result was further supported by noting that the gas laws state that the pressure of a gas is inversely proportional to its volume, so that while atmospheric pressure on the outside of the jar stays constant and the pressure inside goes down, the outside pressure on water in the pan forces the jar's water to go up, leaving less space for the gas molecules and thus increasing their pressure until all pressures are in equilibrium. This combination of steps demonstrates an appropriate application of subject matter knowledge through the use of high-quality examples and relevant supporting evidence. Overall, the purpose of the assignment is fully achieved and reflects an ably reasoned, comprehensive understanding of the topic.

Sample Weak Response to the Constructed-Response Assignment

It is important to have the balanced chemical equation including phases available to evaluate each observer's conclusion. The balanced chemical equation for the burning of the candle is: C sub 25 H sub 52 left paren s right paren plus 38 O sub 2 left paren g right paren equals 25 C O sub 2 left paren g right paren plus 26 H sub 2 O left paren l right paren

This shows that a liquid is being reduced and in closed systems gasses will take up the same space even though there are fewer gas particles at the end. As the temperature drops this and fewer particles will lower the pressure.

Gas laws say the faster the particles move, the higher the pressure because they hit harder which explains the burning candle system. Plus, production of a liquid will raise the level of water.

Observer 1 should not say a vacuum is being formed.

Observer 2 is incorrect because no laws are violated because if you see the balanced chemical equation, the gas laws explain why the closed system must behave that way.

So, to summarize, at first water rises a small amount, which increases, because the gas laws say the gas is cooling.

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 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.

The purpose of this assignment (refer to the instructions for the assignment) is only partially achieved. The writer does provide the correct balanced equation and shows correct phases. However, the statement that "as the temperature drops this and fewer particles will lower the pressure" is an unsupported sentence and is insufficient by itself to discuss temperature/pressure relationships. Moreover, the writer's response to the first bullet includes two unsupported statements about each observer's conclusions about the system. For instance, the statement that the first observer "should not say a vacuum is being formed" does not explain or provide any evidence as to why the statement is incorrect. In addition, the last sentence of the response is unsupported as the gas laws are not described. Overall, this response demonstrates a limited application of subject matter knowledge and a limited, poorly reasoned understanding of the topic.

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.