Thursday, December 18, 2014

Missouri State Mineral - Galena

published on: 2/28/2003

Contributing Teacher(s): Calene Cooper

Subject Area: Science/Life

Grade Range: Middle Grades (6-8)

Materials Needed:

  • triple beam balance
  • sample of galena
  • 2-250ml beakers
  • overflow container
  • 2-10ml graduated cylinders
  • calculator

Process Standards:

  • Goal 1.1 develop questions and ideas to initiate and refine research
  • Goal 1.2 conduct research to answer questions and evaluate information and ideas
  • Goal 1.3 design and conduct field and laboratory investigations to study nature and society

Content Standards:

  • Science 1. Properties and principles of matter and energy
  • Science 3. Characteristics and interactions of living organisms
  • Science 5. Processes (such as plate movement, water cycle, air flow) and interactions of earth’s biosphere, atmos...

    Time Allowance: 2 class periods

    Description: This lesson from a six lesson unit deals with the Missouri Symbol of Galena.

    Comments: This lesson is one of six of a complete unit.


    Classroom Component: Teacher Note: This lesson is a part of a complete unit. Click on the links below to view other individual lessons. Lesson introduction page State Flower--Hawthorn State Fish--Catfish State Aquatic Animal--Paddlefish State Rock--Mozarkite State Tree Nut--Black Walnut

    Background Information: Galena is a sulfur compound of lead and has the chemical formula of PbS. In its purest state, is consists of 86.6% lead and 13.4% sulfur by weight. Some deposits of galena contain silver, zinc, copper, gold so the density or specific gravity may vary from 7.4 to 7.6.

    Density is defined as the amount of mass in a unit or volume of a substance. This means that if one takes a specific volume such as 1cm3of a substance and measures its mass on a balance there is a definite mass for that substance. Density is used to identify samples of minerals, compounds, and other materials. Every pure sample of a material has its own density. The term specific gravity is sometimes used especially in geology and it is the same thing as density.

    There are two main ways to determine the density or specific gravity of a substance such as galena. Both methods require the use of an accurate balance. An overflow container or a graduated cylinder is needed for one method. In the following laboratory exercise try both of these methods on a sample of galena and see how close you get to the accepted density value of galena ore.

    Directions: Specific Gravity Lab Set up the triple beam balance as shown below. Superglue or tie a string onto your sample of galena. Mass the galena on the balance and note how many grams it masses. Raise the balance on a set of books so that the pan hangs over the edge of the books. Tape the string to the edge of the pan so that the sample hangs freely above your work area. Place the sample in a container of water so that it is suspended in the liquid without touching the sides or bottom of the container. Measure the new mass of the sample. Because the galena is suspended in water, it should weigh less. Subtract the wet mass from the dry mass. Divide this difference into the original dry mass to get the specific gravity number. Try this several times and also use several samples of galena. Average your results and compare them to the accepted values of 7.4 to 7.6. Higher numbers denote more pure lead quantity in your sample.

    example

    Directions: Relative Density Lab Another method for determining density calls for the use of a overflow container. This is a container that is filled to the brim with water and when the sample is submerged into it the overflow is captured and measured. The volume of this overflow of water is equal to the volume of the sample. Measure the mass using the balance and divide the mass by the volume to get the density of the sample. Overflow containers can be easily made using a plastic container, a drill, and a straw. If your sample small enough to fit into a graduated cylinder you can observe the change in water level and subtract to measure the sample''s volume. Compare the results of this second method to the results from the specific gravity method. Are there any differences in results? Which method appears to be more accurate?

    example Background Information on Missouri State Mineral - Galena

    Galena, a dark grey metallic lead-sulfite mineral, is the chief ore of the metal known as lead. Major deposits have been mined continuously in Missouri since 1720, especially in the Southeast. Missouri has been the nations major source of lead for 90 years and Missouri has some of the worlds largest deposits.

    The chemical formula for Galena is PbS, which is the element lead, (Pb or the Latin plumbum) and sulfur (S) making it lead sulfite. Trace amounts of other elements found in galena may include zinc, silver, gold, and copper. The ore is mined, concentrated, and then smelted in a blast furnace with limestone and coke. It is refined to remove and recover other metals.

    Uses of lead include: lead-acid storage batteries (80% of all lead used for this), lead alloy solders for electronic connections, lead-based materials for television screens and computer monitors, lead glazes, radiation shielding, and stain glass and lead crystal glass. Because of lead''s relative low melting point, 327.5 oC, it can be remelted and refined easily making the most recycled or reclaimed industrial metal in the world. In the United States about 80% of lead is used in automotive type batteries and more than 95% of these batteries are recycled.

    Pure lead is soft and has little strength so it is alloyed with antimony and tin. Lead also combines chemically with such elements as chlorine and oxygen to form various compounds such as lead sulfite or galena. Lead is highly malleable so it can be pressed into very thin sheets. It has great ductility or the ability to be permanently stretched without breaking. It is non-corrosive is water and resists sulfuric acid and other powerful chemicals. Lead is a poor conductor of electricity. It has an atomic weight of 207.19 and its atomic number is 82. Its density is 11.35 g/cm3.

    While lead has been used by humans for thousands of years, only recently have we discovered the detrimental health effects caused by lead exposure. Ingesting or inhaling high levels of lead can be very harmful. When tetraethyl lead was added to gasoline to improve the performance of automobile engines it was discovered that the by products of burning leaded gasoline produces chemicals that contribute to air pollution. People who lived in high traffic areas suffered from lead exposure. The symptoms of lead poisoning are: fatigue, headaches, stomach cramps, and damage to the brain, kidneys, and liver. Ingestion of lead-based paint chips by children has been shown to cause brain damage leading to learning problems and reduced IQ. Lead based paint and leaded gasoline have been banned in the United States. The mineral galena, because it is a compound where the lead is bound with sulfur, it is a safe mineral to handle.

    In Missouri, mining of galena has flourished in the Joplin-Granby area of southwest Missouri as well as the long time rich deposits found in Crawford, Washington, Iron, and Reynolds County. An interesting area to visit is the Missouri Mine State Historic Site located outside of Park Hills, Missouri (Iron County) in the St. Joe State Park. Here is a museum inside the old Federal Mill Number 3. You can take tours of Missouri mining history and technology. There are many displays and models showing the technology used to make Missouri number 1 in the world in lead production.

    Research Topics

  • Explore the uses of lead.
  • Research the processing of galena ore into lead products.
  • Study the secondary minerals and metals found in galena.
  • Research the history of lead mining in Missouri.
  • Explore the recycling of lead products.
  • Report on the health effects of lead exposure.
  • The best source for Missouri geological information is the Missouri Department of Natural Resources, Division of Geology and Land Survey, P.O. Box 250, Rolla, Missouri, 65401.

    Galena and Lead Websites: What do you think of this lesson? SuccessLink needs to know. Click here to tell us.

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    For additional information contact :
    Calene Cooper
    West Jr. High
    Columbia 93
    (573) 886-2760
    EMAIL:
    ccooper@mail.coin.missouri.edu

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