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Science of the Comstock - Lesson Plans

Lesson Plans:
Introduction
Tour
Physics
Chemistry
Earth Science
Environment
Scams

Chemistry

Introduction

To go with the ore-processing and fire-assay materials in the chemistry section, we include two lesson plans. The lesson on ore processing suggests the students first examine ore minerals and their related metal products, then explore a model ore-processing activity. Last, the lesson suggests that students read the ore-processing material and discuss it to review and extend their understandings. The lesson on fire assaying follows the same scheme, suggesting a model activity, then reading the material and discussing to review and extend the students' understanding.

Ore Processing

Introduction

Processing of Virginia City Ores in the late 1800s

Students study the chemistry of mining in the early days of the Comstock Lode. This lesson is one part of an integrated science unit to study many aspects of the mining of the Comstock Lode through the fields of Earth science, physics, chemistry, and environmental science.

by Elisabeth M. Price, Washoe County School District

Grade Level: Middle School or Introductory High School

Educational Standards Addressed

Educational Standards Addressed (Taken from: National Academy Press, National Science Education Standards, Washington, DC, 1996) ( National Science Education Standards In Adobe Acrobat Portable Document Format) (For Nevada, see also the Nevada State Science Standards, Welcome to the Nevada Department of Education ):

Content Standards for physical science (Standard B), Grades 5-8

--Properties and changes of properties in matter
--Transfer of energy

Content Standards for physical science (Standard B), Grades 9-12

--Structure of atoms
--Structure and properties of matter
--Chemical reactions
--Interactions of energy and matter

Content Standard for history and nature of science (Standard G), Grades 5-8

--History of science

Content Standard for history and nature of science (Standard G), Grades 9-12

--History of science

Skill Standards

--Unifying Concepts: Evidence, models, and explanation
--Develop descriptions, explanations, predictions, and models using evidence.
--Design and conduct a scientific investigation, record observations

Assessment Standards

--Standard C, Assessment tasks are authentic.
--Standard D, Assessment tasks must be set in a variety of contexts

Lesson Overview

Students are introduced to the problem of extracting metals from an ore through the examination of actual ore rocks and the metal product, if available. Such rocks as magnetite or pyrite as an iron ore and malachite or chalcopyrite as a copper ore will illustrate the problem that the metal to be extracted is not present as simply that metal but rather as a compound with properties that are completely different than the metal itself. Samples of the metal, such as paper clips (iron) or electrical wire (copper), will help students see the differences between the ore minerals and the metal itself.

Next, students carry out the model ore processing activity, Metal from Rocks, included on the main ore processing page. This activity gives students experience with some steps of the actual extraction applied in the Comstock ores.

Students read the article about processing ore in Virginia City. Students compare the process described in the ore processing article to their experience extracting metal from their model ore.

To help the students understand the energy involved in mining and processing ore, students now list steps in mining and ore processing in which energy input is needed.

Time Resources

Allow about one half hour for the first activity in which ore rocks and the metal products are examined. The model ore processing with discussion takes about an hour. Reading the article and relating the Washoe Process to the model takes another hour. The final activity of listing energy transfers can be used as an assessment piece, but will take about one half hour. This makes the whole project about 3 hours, but writing observations could double that time.

Instructional Methods and Strategies

The basic instructional principle used here is that of activity before content. Students define the problem with the investigation of ores and metals, explore one partial solution to the problem, then apply that experience to the exploration of the actual process used on the Comstock.

Students need to record observations and steps of the procedure at each step.

During the reading of the ore processing article and relating that process to the model, they should talk in pairs or groups to tease out all the relations and increase understanding.

The energy transfer step is an extension of the activities that enables the student to review the steps in processing ore and apply the concept of use of energy to each step.

Bybee's 5E model of science education can be found in the lesson, too: Engage with the exploration of minerals to have students experience the problem; Explore with the minerals and the model ore processing; Explain in comparing the model ore processing and the actual extraction method used on the Comstock; Elaborate in that comparison and the application to the energy transfer in mining; Evaluate in the recording of observations and finally in the energy transfer portion of the lesson.

Activities

Activity 1 (one half hour plus perhaps some more for recording of observations)

Wear safety goggles when investigating the properties of minerals and metals.

Students explore the properties of ore rocks such as magnetite, pyrite (iron ores), chalcopyrite, and malachite (copper ores). Students should determine the properties to study, but should include the traditional rock properties such as hardness, luster, streak, magnetism, conductivity (heat or electrical) ductility and malleability (wear safety goggles) properties. Compare these properties to those of the metals that come from the ore rocks: iron paper clips or other iron object, copper electrical wire. The properties should include the same ones studied for the minerals. Record observations and draw conclusions about the properties of ore minerals compared to the properties of the metals.

Extension discussion: What uses are made of the properties of the metals as they are used in every day products? (List products that use the metals first.)

Activity 2 (one hour plus more if students want to explore methods of increasing production or reclaiming the heap)

Wear safety goggles when adding the "ore" to the "heap" and when using ammonia.

Students simulate one method of recovering metal from rocks by leaching a simulated copper ore with water, then reducing the copper in solution to copper metal with paper clips or steel wool. Follow the directions in the lab activity, Metal from Rocks, for Ore Processing.

Activity 3 (about one hour)

Read the method of ore processing used in Virginia City. In a group or with a partner, students identify the steps of the Washoe Process that are the same or similar to that of the simulated ore processing. Students also discuss differences and perhaps suggest changes in either method to improve it is some way (efficiency, environmental concerns). The discussion of the driving force for the reactions in the article provides an opportunity to address oxidation/reduction potentials for high school students.

Record comparisons.

Activity 4 (about one half hour) (can be used as an assessment along with the recorded observations and comparisons)

In a group or individually for assessment, review the steps of processing ore (might include mining). List the steps that require the input of energy. Decide what type of energy needs to be input and the source of the energy.

Lesson Assessments

Embedded Assessment can be taken from the observations and comparisons made between the model ore processing and the actual Washoe Process. Look for statement of physical handling of the ore, statement of chemical reactions, and statement of products that result.

In the related energy transfer activity, look for the list of steps of processing the ore, those steps that are selected for addition of energy (virtually all steps), and the definition of type of energy needed (such as heat in the Washoe Process, or kinetic energy to crush the ore and mix the ore, or chemical energy in the reduction of silver in a compound to silver metal).

Fire Assaying

Introduction

by Elisabeth M. Price, Washoe County School District, Nevada

Grade Level: Middle School or Introductory High School

Educational Standards Addressed

Content Standards for physical science (Standard B), Grades 5-8

--Properties and changes of properties in matter
--Transfer of energy

Content Standards for physical science (Standard B), Grades 9-12

--Structure of atoms
--Structure and properties of matter
--Chemical reactions
--Interactions of energy and matter

Content Standard for history and nature of science (Standard G), Grades 5-8

--History of science

Content Standard for history and nature of science (Standard G), Grades 9-12

--History of science

Skill Standards

--Unifying Concepts: Evidence, models, and explanation
--Develop descriptions, explanations, predictions, and models using evidence.
--Design and conduct a scientific investigation, record observations

Assessment Standards

--Standard C, Assessment tasks are authentic.
--Standard D, Assessment tasks must be set in a variety of contexts

Lesson Overview

Students investigate the collection of suspended particles in water by a gelatinous precipitate as a model for the collection of precious metals in molten rock samples by lead in the fire assay method. Then students read about the technique of fire assay as applied in the late 1800s and today and relate the model lab activity to the reading. Students then analyze the fire assay method to predict the steps in which error may be introduced.

Time Resources

The introduction may be 15 minutes. The lab activity takes about one hour including the set-up and writing of observations. Reading the fire assay article and making comparisons should take about one half hour. Analyzing the fire assay method for introduction of error may take about one half hour. The whole lesson should take about 2.25 hours.

Instructional Methods and Strategies

The activity places the lab investigation before the reading in order to provide students with some experience so the reading has more meaning. (Activity Before Content)

During the lab investigation, students manipulate equipment, record observations in pictures and words, and have the opportunity to suggest changes to the method provided.

Bybee's 5E model can be used: Engage the students by introducing the problem of knowing before actually mining the rock if there is silver and gold in it and, if so, how much. Students Explore some of the processes involved in fire assay using the model of collecting clay particles suspended in water with a gelatinous precipitate. Students Explain the reading selection through reference to their lab investigation. Students Elaborate on the lab investigation through the reading selection and through the evaluation of the fire assay method for introduced errors. Students Evaluate through the listing of the steps of fire assay and considering introduced errors.

Activities

Activity1: Introduction. (about 15 minutes)

Introduce the need for assaying by referring to the ore processing activity "How did the miners know which rocks had silver in them so after all that processing they would make money?" Students discuss in their group ways they might have known. (Seeing the silver containing minerals, mining a little bit first) Actually, because the miners were looking for gold, the mines opened as gold mines. Initially the silver ore was not recognized and was discarded as "blue mud."

Activity 2: Collection of clay suspension in water. Wear safety goggles when doing lab exercises. (about one hour including writing observations and procedure)

This is a model for one step of the method used for finding out the amount of precious metal in a sample. The suspended clay (representing the precious metal throughout the rock) is collected by alum. Follow the method in the Lab Activity with Fire Assaying.

Activity 3: Read about the actual Fire Assay method (about one half hour)

The Fire Assay article describes the method of fire assaying that was used in Virginia City in the late 1800s and is still used today. Read the article and discuss how the method works. List the steps and compare the lab activity to the reading to find similarities and differences.

Activity 4: Summarize (about one half hour)

Summarize the steps of the fire assay method. Consider errors that could be introduced at each step and suggest ways either to reduce the errors or to know if the errors actually occurred.

Lesson Assessments

Embedded assessment can include descriptions of observations during the lab activity, any notes taken during the reading activity, and relating the lab activity to the reading. Look for completeness of observations and thoroughness of relation of lab activity to the reading. Activity 4 can be used as an assessment or extension. Look for a clear listing of the steps of the fire assay method and suggestions of possible error and means of knowing the errors occurred. An exemplary discussion of errors would suggest if the errors would be large enough to be noticed in the final result.