Read ANALYSIS OF COPPER(II) SULFATE FOR PERCENT WATER text version

Cover Sheet Teacher-Developed Classroom Units and Assessments

___Unit ___Assessment

Mary Ann Varanka-Martin, Estes Park High School AUTHOR(S): _________________________________________ Marsha Mowery, Rocky Mountain High School _____________________________________________________ Matt Nigro, Loveland High School _____________________________________________________ Mike Petraglia, Greeley West High School _____________________________________________________ _____________________________________________________ Analysis of Copper(II) Sulfate for Percent Water TITLE:______________________________________________ _____________________________________________________ _____________________________________________________ Science Standards 1, 2.1, 2.3 (Chemistry/Physical SUBJECT AREA(S):___________________________________ Science) _____________________________________________________ _____________________________________________________ _____________________________________________________ Secondary, Grades 9-12 GRADE LEVEL/AUDIENCE:___________________________ _____________________________________________________ _____________________________________________________ 1997 DATE:_______________________________________________ Independent Reviewer, Northern Colorado BOCES. REVIEWED BY:______________________________________ Approved July 1997 _____________________________________________________ _____________________________________________________ 1997 Mary Ann Varanka-Mowery, COPYRIGHT INFORMATION: ©_______________________ Marsha Mowery, Matt Nigro, Mike Petraglia. _____________________________________________________ _____________________________________________________ This material may be reproduced for classroom use.

Colorado Department of Education Standards & Assessment Resource Bank

Part 1

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Title Page

Assessment Title: Analysis of Copper(II) Sulfate for Percent Water School Level: Secondary 9-12 Grade - Estes Park H.S. - Rocky Mountain H.S. - Loveland H.S. - Greeley West H.S.

Assessment Authors: Mary Ann Varanka-Martin Marsha Mowery Matt Nigro Mike Petraglia

Standards Assessed: Science Standard #1 Students understand the processes of scientific investigation and design, conduct, communicate about, and evaluate such investigations. Benchmarks: · identifying major sources of error or uncertainty within an investigation(for example, particular measuring devices and experimental procedures). · communicating and evaluating scientific thinking that leads to particular conclusions Science Standard # 2 Students know and understand common properties, forms, and changes in matter and energy. Science Standard # 2.1 Students know that matter has characteristic properties, which are related to its composition and structure. Benchmarks: · Using word and chemical equations to relate observed changes in matter to its composition and structure. Science Standard # 2.3 Students understand that interactions can produce changes in a system, although the total quantities of matter and energy remain unchanged. Benchmarks: · identifying, describing, and explaining physical and chemical changes involving the conservation of matter and energy (for example, oscillating pendulum/spring, chemical reactions, nuclear reactions). · observing, measuring, and calculating quantities to demonstrate conservation of matter and energy in chemical changes (for example, acid-base, precipitation, oxidation-reduction reactions), and physical interactions of matter (for example, force, work, power)

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Part 2

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Assessment Prompt for Students

Background Information You are the quality control officer for Acme Computer Company, Printed Circuit Division in Boise, Idaho. A process problem has developed with the copper electroplating bath which utilizes a hydrate of copper(II) sulfate as a major component in the electroplating solution. It is very important that the copper(II) sulfate be a specific hydrate, and there is suspicion that the vendor's quality may have slipped and you are being supplied with an improper hydrate of the copper(II) sulfate. Hydrates are ionic compounds (salts) that have a definite amount of water as part of their structure. This "water of hydration" is released as vapor when the hydrate is heated. The remaining solid is known as the anhydrous salt, and often the change to the anhydrous salt is indicated by a color change. The general equation for the dehydration process is hydrate + Heat -----> anhydrous salt + water As a quality control officer your job is to determine if the vendor is meeting your specifications and supplying your division with the correct compound of hydrated copper(II) sulfate. The percent water in the sample can be determined by following Process Control Document 42.15, "Percent Water in Copper(II) Sulfate." In this procedure, the percent water in a hydrate can be determined experimentally by accurately determining the mass of the compound in question, carrying out a procedure to dehydrate the compound, massing the anhydrous salt and calculating the percent water. The formula of the hydrate (CuSO4 . XH2O), where "X" is the number of molecules/moles of water for each formula unit/mole of copper(II) sulfate, can then be determined. In addition, the process requires verification of your results by rehydrating your anhydrous sample. The quality control document is reproduced for you on the following page.

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Part 2

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Assessment Prompt for Students

QUALITY CONTROL DOCUMENT 42.15 DETERMINATION OF WATER CONTENT IN COPPER(II) SULFATE Purpose: To determine the percent water and waters of hydration in copper(II) sulfate. Materials: sample copper(II) sulfate hydrate evaporating dish ring stand with ring Bunsen burner or hot plate stirring rod crucible tongs weigh boats weighing paper balance droppers wire gauze

Procedure for Percent Water in Copper(II) Sulfate: 1. Prepare the setup as required to heat an evaporating dish over a Bunsen burner or hot plate. 2. Develop a clear and concise data table. 3. Heat the empty evaporating dish for three minutes. 4. Use the crucible tongs to remove the evaporating dish from the ring and place it on a wire gauze. Let it cool for several minutes. 5. Find the mass of the evaporating dish. 6. Mass out about 2 grams of the copper(II) sulfate hydrate. 7. Place the hydrate in the evaporating dish, and gently heat the evaporating dish. Avoid any popping and spattering. As the hydrate is being heated, stir with the stirring rod. 8. Heat it strongly for 3 minutes after the blue color has disappeared. 9. During the heating, the stirring rod may be used to "spread" the solid and break up any "caked" portions of the hydrate. Be careful not to pick up any solid on the stirring rod. If the edges of the solid appear to be brown, remove the heat momentarily and resume heating at a gentler rate. 10. Allow the evaporating dish to cool, and then immediately measure the mass of the evaporating dish with anhydrous salt. 11. Completely transfer the anhydrous salt to a premassed weigh boat. 12. Add distilled water drop-wise with stirring until the salt is rehydrated. 13. Let any excess water evaporate overnight and mass the rehydrated salt.

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Part 2

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Assessment Prompt for Students

Calculations: 1. Find the mass of water lost. 2. Find the percent water in the hydrate. 3. Find X in CuSO 4 . XH2O 4. Find the mass of water required to rehydrate the compound using your experimental data. Analysis of Procedure and Results: 1. Write word and chemical equations for the changes you observed. 2. What sources of experimental error would result in too many waters of hydration in the calculated formula? * 3. What sources of experimental error would result in too few waters of hydration in the calculated formula? * 4. Does this procedure demonstrate conservation of matter? If so why? If this procedure does not demonstrate conservation of matter, how would you modify the experiment to demonstrate conservation of matter? 5. Does this procedure demonstrate conservation of energy? If so why? If this procedure does not demonstrate conservation of energy, how would you modify the experiment to demonstrate conservation of energy? * Explain how these sources of experimental error would effect your data and result in too many or too few waters of hydration?

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Part 3 - Assessment Scoring Guide

Scoring Guide: Analysis of Copper (II) Sulfate for Percent Water Levels Observations: Not Proficient

· no qualitative observations ·

Basic

few qualitative observations, are brief and nondescriptive ·

Proficient

some qualitative observations recorded, are partially complete, and descriptive ·

Advanced

qualitative observations are numerous, complete and highly detailed recorded before, during and after each experiment

·

·

Measurements/ Reports

absent or incomplete data table

·

data table(s) present & complete

·

data table(s) well organized, labeled, & complete most data reported must have units & must be reported to correct number of significant digits

·

data table(s) well organized, labeled, & complete all data reported must have units & must be reported to correct number of significant digits evidence of repeated experimentation

·

most data reported must have units

·

·

·

Calculations

·

required calculations and results mussing

·

most calculations included

·

most formulas for calculations are included most calculations included correct most numbers are given correct units

·

all formulas for calculations are included all calculations included & correct all numbers are given correct units

· ·

· ·

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Part 3 - Assessment Scoring Guide

Levels Calculations

(continued)

Not Proficient

Basic

Proficient ·

Advanced

all results easy to find, labeled, & reported to correct number of significant digits data from repeated experimentation is used

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Analysis

Equations:

· word & chemical equations missing · word or chemical equation correctly written for dehydration or rehydration some sources of experimental error are legitimate · word & chemical equations correctly written for dehydration or rehydration most sources of experimental error are legitimate · word and chemical equations correctly written for dehydration and rehydration all sources of experimental error are legitimate & stated in complete sentences analysis of sources of experimental error is included, accurate, & complete correct analysis which shows extensive & sophisticated understanding of conservation of matter and energy

Error:

·

sources of experimental error are missing

·

·

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Conservation of Matter and Energy:

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experimental error analysis is included & partially correct

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experimental error analysis is included & mostly correct

·

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no discussion of conservation of matter and energy or discussion shows no understanding of conservation of matter and energy

·

correct analysis which shows limited understanding of conservation of matter and energy

·

correct analysis which shows more in-depth understanding of conservation of matter & energy

·

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Part 4 - Preparation and Administration Instructions Essential Prior Learning in Science The student: · should have a basic knowledge of laboratory safety, laboratory technique (especially use of Bunsen burner), methods of chemical disposal, and data table preparation. · should have skills in laboratory observation and proper techniques for making, recording and displaying observations, this includes carrying out repeated experiments for analysis of precision. · should be able to correctly label all measurements. · should be able to read measurements to the correct number of significant digits. · should be able to write formulas for all calculations. · should be able to calculate percent composition and moles from mass. (For advanced proficiency, students should be able to generate and report results to the appropriate number of significant digits.) · should be able to write chemical formulas and word and chemical equations. · should be able to identify sources of experimental error and analyze their effect on the final product. · should have a basic knowledge of conservation of matter and energy. · should be able to apply many higher order thinking skills, including analysis, evaluation, inductive reasoning, prediction, and synthesis. · "Legitimate" sources of error must be discussed. (e.g. errors in use of the calculator vs spattering of substance). Assessment Administration Guidelines · This task may be done using small scale techniques by modifying the procedure appropriately. · Pass out a copy of the prompt and the rubric. Read through the material with your students and answer any questions regarding the task or evaluation criteria. · Allow 1 to 2 class periods for completion of the task. · This task requires the pentahydrate of copper (II) sulfate (CuSO4 · 5 H 2O). · The laboratory procedure can be done by lab groups, but should be analyzed by students working individually and independently. · The number of experimental repetitions that can be completed during a class period will vary based on the length of the period (48 minute period vs 90 minute block). THE ANHYDRIDE MUST BE MASSED BEFORE THE END OF THE CLASS PERIOD FOR ACCURATE RESULTS. THE ANHYDROUS COMPOUND CAN NOT BE LEFT OVERNIGHT WITHOUT MASSING. The sample may gain water from the atmosphere.

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Part 4 - Preparation and Administration Instructions · Rehydrate in a plastic weigh boat if evaporating dishes are in short supply. · Try placing the rehydrated sample in a desiccator for a few hours before massing to remove any excess water. · Student observations should include: · a color change from blue to white and back to blue through the processes of dehydration and rehydration · a temperature change on rehydration, demonstrated by sizzling and a qualitative increase in temperature · Measurements include: · the initial mass of the empty evaporating dish · the mass of the sample and the evaporating dish · the mass of dehydrated salt and evaporating dish · mass of empty weighing boat · mass of rehydrated sample and weighing boat · Sources of experimental error include · spattering --due to heating too quickly, over too high a flame will result in too many waters of hydration · insufficient heating, water is still present in the sample, will result in too few waters of hydration · loss of sample on equipment, will result in too many waters of hydration · rehydration problems --- excess rehydration water in final weighing, not adding sufficient water to fully hydrate or not transferring all the dehydrated sample into the weigh boat, will not effect "X", but will effect mass of water required to rehydrate compound. · high humidity will result in too few waters of hydration if not weighed immediately · weighing too long after the dehydration is completed will result in too few waters of hydration · Percent error can be calculated, but the actual value (36.0%) needs to be given to students. If this information is given too early in the process, students could "create" data rather than producing it from experience. · The equations for dehydration are: · copper(II) sulfate pentahydrate plus heat yields anhydrous copper(II) sulfate and water, and · CuSO4 · 5 H 2O + heat -----> CuSO4 + 5 H2O · The equations for rehydration are · anhydrous copper(II) sulfate and water yield copper(II) sulfate pentahydrate and heat, and · CuSO4 + 5 H2O ------> CuSO4 · 5 H 2O + heat · The rehydrated salt can be recycled and used the next time this assessment is used.

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Part 4 - Preparation and Administration Instructions · The first two waters of hydration escape from the hydrate at temperatures around 30%C. Two more waters of hydration escape from the hydrate at temperatures around 110%C, and the compound becomes anhydrous by 250%C. The compound will decompose above 560%C. · When using the scoring guide, scoring the student's analysis of conservation of matter and energy, the teacher has to make the decision if there is an "and" or an "or" between matter "and" energy. · As the scoring guide is written, repeated experimentation are required for an advanced score. If the instructor feels that repeated experiments are not possible or desirable please feel free to delete. · This scoring guide has not been assigned any point values or weights. It is left to the individual teacher to determine how to use this scoring guide in assigning "grades". Please make sure students know how this scoring guide will be used before putting it in their hands. · The value for "X" may be calculated in a number of ways, two in particular are noted here: 1)

36% = X . 18 x 159. 6 + (X . 18) 100

where: X = 18 = 159.6 = (X · 18) = 2)

waters of hydration molecular mass of water molecular mass of CuSO 4 molecular mass of waters of hydration = X

moles of water released from hydrate moles of anhydrous CuSO 4

· The students' analysis of conservation of matter and energy may vary with their understanding and expertise. There is no definitive answer, yes or no, to this question, it depends on their analysis. For example:

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Part 4 - Preparation and Administration Instructions · Conservation of mass: "This experiment does demonstrate conservation of mass. When I evaporated and then added water, the mass was close to the same. There was no mass lost or gained in the transfer." "This lab does not demonstrate conservation of matter because we do not account for the water that is evaporated out of the hydrate. Even though it is common knowledge that this water simply evaporates, the lab would have more accurately demonstrated conservation of matter had it involved collecting the water vapor which is released from the hydrate. Had I done this, I would have been able to condense the water vapor and measure its mass, thus accounting for the water lost which would demonstrate the conservation of matter." While both of these student responses are correct, the second demonstrates a sophisticated understanding of the concept. · Conservation of energy: "This experiment does not demonstrate conservation of energy. Energy could have been lost in the form of heat when we rehydrated. I didn't measure the temperature change so I wouldn't know if energy was lost or gained. If I measured the temperature before and after the reaction, I could tell if energy was conserved." "This lab also adequately demonstrates the law of conservation of energy. When we dehydrated the Cu(II) sulfate, heat was added to the system. When we then rehydrated the Cu(II) sulfate, heat was given off and the system balanced out. We could better prove this by measuring how much heat was added and how much heat was given off. Then we could compare the results to see if energy is constant."

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Part 5 - Accommodations and Modifications

ACCOMMODATIONS LIST · Present assessment material in a more organized, easy-to-follow format (e.g., more white space, fewer items on a page, headings and subheadings, important ideas in bold type). · Use preferential seating to place the student closer to the source of the oral instructions and/or demonstration equipment. · Allow the student access to textbooks and other resources during the assessment. · Provide a more private environment for the student, without social, auditory, or visual distractions. · Provide an opportunity for the student and teacher to discuss the instructions to ensure understanding. · Administer the assessment individually to the student, this may be done after school, before school or whenever the teacher thinks is appropriate. · Give the student more time to complete the assessment. · Allow the student to take the assessment when he/she is in a non-agitated noncrisis mode. · Permit the student to take the assessment more than once. · Permit the use of technology, such as calculators, word processors, spell checkers, or tape recorders. · Permit the use of whatever augmentative or assistive technology the student uses on a daily basis (e.g., magnifying equipment, noise buffers). · Provide more supervision for the student, encouraging him/her to stay on task. · Allow the student to move around the room during the assessment session, as long as this does not interfere with safety in the lab. · Read the assessment aloud to the student, or provide an oral presentation of the assessment on audio or video tape. · Record or script answers as the student dictates them.

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Part 5 - Accommodations and Modifications

· Add more complex and/or open-ended items requiring thinking at greater levels of creativity and/or depth to challenge gifted and talented students and to fully assess their knowledge and skill levels. · Deliver the assessment in large print, in Braille, in sign language, or with a picture board. · Deliver the assessment in the student's preferred language, and/or allow him/her to respond in that preferred language. · Coach the student and critique assessment work in progress so that the student receives useful feedback and encouragement.

MODIFICATIONS LIST · Provide organizational aids such as templates of data tables. · Permit the student to take portions of the assessment, while being exempted from other portions.

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