Elemental mercury and its compounds—Environmental impact of mercury and how it is converted to compounds of mercury such as methylmercury is explained. This could be used as you are teaching about elements and the periodic table.
Properties—You can cite parts of the article when discussing physical and chemical properties of mercury.
Oxidation—Elementary mercury is oxidized to mercury(II) ions, Hg2+. This is an excellent example to use as you are teaching about oxidation and reduction.
Organic chemistry and functional groups—The article explains the formation of methylmercury. The explanation includes methyl groups (–CH3) and thiol groups (–SH).
Concentrations—The article explains how the mercury concentration increases as it moves up the food chain. This process is referred to as biomagnification
Parts per million—This is the unit of concentration used to measure trace amounts of mercury in fish. This could be used as a real world example when teaching various units of concentration.
Possible Student Misconceptions
(to aid teacher in addressing misconceptions)
“It is better to avoid eating fish because of the mercury.”According to the American Heart Association all Americans should eat at least two fatty fish meals a week to improve heart health. The risk from mercury by eating fish and shellfish is not a major health concern. The health risks of not eating fish far outweigh the risk of mercury toxicity. However, people should avoid eating shark, swordfish, king mackerel and tilefish because of their high mercury content.
“Vaccines contain mercury and should be avoided.”A mercury-based preservative called thimerosal has been used for decades in the United States in multi-dose vaccines. It is added to the vials of vaccine to prevent the growth of bacteria and fungi. There is no evidence of harm caused by the low dose of thimerosal in vaccines. In 1999, vaccine manufacturers agreed to reduce or eliminate the amount of thimerosal in vaccines as a precaution. According to the Centers for Disease Control and Prevention, measles, mumps, and rubella vaccines do not and never did contain thimerosal. Neither do chickenpox, inactivated polio and pneumococcal vaccines. Influenza vaccines are available with and without thimerosal.
Anticipating Student Questions
(answers to questions students might ask in class)
“Does cooking eliminate mercury from the fish?”Cooking does not change the concentration of mercury in fish. Methylmercury is bound to the proteins in the fish’s muscle. To vaporize the mercury from the fish it would have to be heated to 357 oC (674 oF), which would never happen because the fish would burn first.
“My mother says her fillings contain mercury. Is that dangerous?”The safety of the mercury amalgam fillings is a controversial topic. They do release low levels of mercury vapor that can be inhaled and absorbed by the lungs. The U.S. Food and Drug Administration (FDA), after reviewing scientific evidence to determine whether these low levels of mercury vapor are a problem, considers mercury dental amalgams safe for children over 6 and adults. In addition
The ADA Council on Scientific Affairs prepared a comprehensive literature review on amalgam safety that summarized the state of the evidence for amalgam safety (from January 2004 to June 2010). Based on the results of this review, the Council reaffirmed at its July 2009 meeting that the scientific evidence supports the position that amalgam is a valuable, viable and safe choice for dental patients.
Students can interact with a simulation of biomagnification of mercury at this site. It also includes follow-up questions that help with their understanding. (http://oceanexplorer.noaa.gov/edu/learning/player/lesson13/l13la1.html)
Students could participate in a food web game that demonstrates the biomagnification of substances such as mercury. The following sites have explicit directions on how to conduct such an activity:
In this game the students play the role of grasshoppers, shrews, or hawks. The grasshoppers will be given a bag of “food,” which consists of white paper squares, and “mercury” (colored paper squares). Students will collect the “mercury” as it moves up the food chain. (http://participatoryscience.org/curriculum-activity/food-chain-game)
Bioaccumulation and Food Chains is a similar activity using colored tokens or poker chips. In this game the students are either zooplankton, rainbow trout, walleye or eagles. This game is followed by an extensive analysis of the data collected, leading to students differentiating between bioaccumulation and biomagnification. The instructions can be found at the end of this site, on page 44: http://sharkresearch.rsmas.miami.edu/assets/pdfs/learning-tools/high-school/MODULE%205%20Management,%20Conservation,%20Research%20and%20Actions%20-%20SECTION%203%20Mercury%20Toxicity%20Data.pdf.
Biomagnification can also be demonstrated using food coloring and water. This can be done either as a teacher demonstration or a simple laboratory activity for students. Instructions for this can be found on page 15 of this site: http://sharkresearch.rsmas.miami.edu/assets/pdfs/learning-tools/high-school/MODULE%205%20Management,%20Conservation,%20Research%20and%20Actions%20-%20SECTION%203%20Mercury%20Toxicity%20Data.pdf.
In an activity called Mercury in the Environment: Percent Mercury in Coal, students can determine the percent-by-mass of elements in coal. The “coal sample” is a bag of different colored beads. Each color represents a different element. The most abundant colored bead will represent carbon. An explanation and instructions for this activity can be found beginning on page 26 of http://sharkresearch.rsmas.miami.edu/assets/pdfs/learning-tools/high-school/MODULE%205%20Management,%20Conservation,%20Research%20and%20Actions%20-%20SECTION%203%20Mercury%20Toxicity%20Data.pdf.
A series of lessons on mercury including mercury in the environment and mercury in the food chain can be found at http://www.kendallville-in.org/pdf/mercury/mercury_high_school_activity.pdf.
“The Ups and Down of Thermometers” is an interactive lesson on thermometers produced by the American Chemical Society. It is designed for middle school but could be adapted for older students as well. (http://www.middleschoolchemistry.com/lessonplans/chapter1/lesson3)
You can use analogies to help students understand measurements that are either very large or very small. The activity at http://www.toxicsaction.org/sites/default/files/tac/sfa/messaging_with_analogies.pdf provides students with practice understanding various units.
Students can investigate the meaning of parts per million using a 10% solution and diluting it until its concentration is one part per million. As description of such an activity can be found at http://ed.fnal.gov/trc_new/sciencelines_online/fall96/activities.html.
Along the same lines as the activity above, an excellent example of a serial dilution laboratory activity can be found at this site: http://www.lcsd.wednet.edu/cms/lib06/WA01001184/Centricity/Domain/14/Serial_Dilution_Lab.pdf.
Out-of-Class Activities and Projects
(student research, class projects)
Students could research the pros and cons of eating fish and write a position paper on the topic.
Students could be assigned to research and write about the industrial uses of mercury. Topics could include the use of mercury in gold mining, in iron mining and in chlorine and polyvinyl chloride production.
Students could also be assigned to investigate and report on the major sources of mercury in the environment, which could include power plants, pesticides, and volcanos. It could also include an investigation of China’s contribution to mercury pollution.
Students could research and report and, possibly, debate in class the use of mercury in dental amalgams. The health effects on the human body (or lack thereof) due to amalgam fillings is a topic of ongoing scientific research and debate.
Students could research and report on other contaminants that biomagnify in fish and pose hazards for humans. These could include PCBs, DDT, dioxin, and chlordane.
The references below can be found on the
ChemMatters 30-year DVD, which includes all articles
published from the magazine’s inception in October 1983 through April 2013, all available Teacher’s Guides, beginning February 1990, and 12 ChemMatters videos. The DVD is available from the American Chemical Society for $42 (or $135 for a site/school license) at this site: http://ww.acs.org/chemmatters. Scroll all the way down to the bottom of the page and click on the icon at the right, “Get the past 30 Years of ChemMatters on DVD!” Selected articles and the complete set of
Teacher’s Guides for all issues from the past three
years are available free online at the same Web site, above. Click on the “Issues” tab just below the logo, “ChemMattersonline”.
30 Years of ChemMatters!
(non-Web-based information sources) Graham, T. Mystery Matters: Nightmare on White Street. ChemMatters, 1996, 14 (4), pp 9–11. This article relates the story of four people poisoned by mercury vapors created by the smelting of mercury amalgam to recover the silver.
Rohrig, B. Thermometers. ChemMatters, 2006, 24 (4), pp 14–17. This article describes the history of thermometers and describes a variety of different types of thermometers, including the mercury thermometer.
Sitzman, B. and Goode, R. Open for Discussion: Lighten Up! ChemMatters, 2012, 30 (4), p 5. This one page article describes how fluorescent light bulbs work. It also describes the advantages and disadvantages of using them.
Web Sites for Additional Information
(Web-based information sources)
More sites onbiomagnification and bioaccumulation Biomagnification and bioaccumulation are explained and compared at this site: https://environment.knoji.com/what-is-the-difference-between-bioaccumulation-and-biomagnification/.
This site also explains both biomagnification and bioaccumulation. It also describes the biomagnification of various pollutants such as DDT, heavy metals, PCBs, and cyanide. (http://w3.marietta.edu/~biol/102/2bioma95.html)
This short video (2:21) clearly explains the biomagnification and bioaccumulation of DDT. The graphics make the concepts very clear. (https://www.youtube.com/watch?v=FoKgsLEm_XA)
At this site there is information on bioaccumulation and biomagnification of mercury. It also has a variety of activities that help to teach these concepts. It would make an excellent resource for developing lesson plans on these topics. (http://sharkresearch.rsmas.miami.edu/assets/pdfs/learning-tools/high-school/MODULE%205%20Management,%20Conservation,%20Research%20and%20Actions%20-%20SECTION%203%20Mercury%20Toxicity%20Data.pdf)
More sites onmercury History of mercury A concise history of the discovery and early uses of mercury can be found at this site: http://www.chemicool.com/elements/mercury.html.
More historical information about mercury can be found here: http://nature.berkeley.edu/classes/eps2/wisc/hg.html.
Properties of mercury Interesting facts about mercury are given at this site: http://www.livescience.com/39232-facts-about-mercury.html.
This site contains information on the discovery, properties, occurrence, uses, and health effects of mercury. (http://www.chemistryexplained.com/elements/L-P/Mercury.html)
At this site a tabulation of information about mercury is given. It includes general information, physical and chemical properties, the application, environmental problems and toxicity of mercury. (http://www.uwm.edu.pl/kchem/mercury/mercury.html)
This video (5:12) produced by the Royal Society of Chemistry discusses and demonstrates characteristics of mercury. It is a safe way to observe the liquid metal. (http://www.rsc.org/periodic-table/video/80/Mercury?videoid=oL0M_6bfzkU)
Uses of mercury This article describes the production of chlorine using the mercury cell process. It includes an animated illustration that clearly shows the process. (http://www.eurochlor.org/the-chlorine-universe/how-is-chlorine-produced/the-mercury-cell-process.aspx)
An explanation of how a mercury switch works is given at this site: http://www.wisegeek.com/what-is-a-mercury-switch.htm.
This article provides a detailed explanation, including graphics, on how a fluorescent bulb works. (http://home.howstuffworks.com/fluorescent-lamp.htm)
This EPA site briefly describes the use of mercury batteries today: http://www.epa.gov/mercury/mercury-batteries.
The use of mercury thermometers at home, for educational purposes, and in industry is described at this EPA site. It also discusses the phasing out of these thermometers as well as restrictions on their use. (http://www.epa.gov/mercury/mercury-thermometers)
A short article that describes mercury amalgams and also gives their advantages and disadvantages can be found here: http://web.health.gov/environment/amalgam1/amalgamu.htm.
Mercury is shown dissolving gold (forming an amalgam) in this short video (1:56). (https://www.youtube.com/watch?v=gKxCw889qck)
Mercury in the environment This site gives information on the some of the top mercury pollution sources and what can be done about them. (http://www.rodalewellness.com/health/mercury-pollution-and-exposure)
An extensive article on mercury pollution in the marine environment can be found at this site. This report was compiled by the Coastal and Marine Mercury Ecosystem Research Collaborative at Dartmouth College. It includes information on the processes related to the inputs, cycling, and uptake of mercury in marine ecosystems; effects on human health; and policy implications. (http://www.dartmouth.edu/~toxmetal/assets/pdf/sources_to_seafood_report.pdf)
This article from Chemical and Engineering News describes the legislation made by the EPA to limit the emissions of mercury by power plants and its review by the Supreme Court. (http://cen.acs.org/articles/93/i18/High-Court-Weighs-EPA-Mercury.html)
The National Park Service created this video (4:21) that is filmed in Acadia National Park. It describes how mercury gets into the air and pollutes the environment. It includes a description of biomagnification and how wildlife is affected. (https://www.youtube.com/watch?v=xRqAS4Eow-c)
Mercury poisoning and its effects on health This article by the World Health Organization describes how one is exposed to mercury and how to reduce one’s exposure. The health effects of mercury exposure and poisoning are also described. (http://www.who.int/mediacentre/factsheets/fs361/en/)
This detailed article describes exposure to mercury. It explains the metabolism and toxicity of both elemental mercury and inorganic mercury. (http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3514464/)
This Chemistry and Engineering News article explains how methylmercury enters the body and the reactions it undergoes. It describes the effects of the methylmercury on the body. (http://pubs.acs.org/email/cen/html/033007161508.html)
At this site the health effects and symptoms of mercury poisoning are described. It specifically describes the health effects of methylmercury, elemental mercury and inorganic mercury. (http://www.medicinenet.com/mercury_poisoning/page3.htm#what_are_the_health_effects_and_symptoms_of_mercury_exposure_or_poisoning)
In this article the phrase “mad as a hatter” is explained. It describes the production of felt hats and how the hatters were exposed to and poisoned by mercury. (https://www.cas.org/news/insights/science-connections/mad-hatter)
More sites onadvantages and disadvantages of eating fish This Harvard School of Public Health article explains the benefits of eating fish. It also describe some possible risks. (http://www.hsph.harvard.edu/nutritionsource/fish/)
The article at this site states and explains eleven benefits of eating fish. (http://authoritynutrition.com/11-health-benefits-of-fish/)
The U.S. Food and Drug Administration cites facts about the benefits of eating fish. It provides safety tips for the consumption of fish. In addition the article answers commonly asked questions about mercury in fish. (http://www.fda.gov/food/resourcesforyou/consumers/ucm110591.htm)
A quick reference card that states which fish have the least, moderate, high and very high mercury content can be found at the site. This is suitable for printing. (http://www.nrdc.org/health/effects/mercury/walletcard.pdf)
The levels of mercury in fish are given at this U.S. Food and Drug Administration site: http://www.fda.gov/Food/FoodborneIllnessContaminants/Metals/ucm115644.htm.
A mercury calculator is available at this site. You enter your weight, the type of seafood and the amount you eat to determine the amount of mercury you consume per week. (https://seaturtles.org/programs/mercury/)
More sites on trace measurement units This article clearly explains the parts per million and parts per billion units. It also provides some excellent analogies to help in the understanding of the size of these units. (http://www.nesc.wvu.edu/ndwc/articles/ot/fa04/q&a.pdf)
At this site ppm is defined. Sample problems and sample calculations are also provided. (http://www.chemteam.info/Solutions/ppm1.html)
At this site measurement units and analogies are given in a table format. It could serve as a quick reference. (http://www.llojibwe.org/drm/environmental/content/concentrations.pdf)