Mercury

Introduction: (Initial Observation)

While Mercury is one of the most useful of the heavy metals found in our daily lives, it is also one of the most deadly. When carelessly handled or improperly disposed of, Mercury gets into drinking water, lakes, rivers and streams and becomes a clear threat to human health and the environment.

Information Gathering:

Find out about what you want to investigate. Read books, magazines or ask professionals who might know in order to learn about the effect or area of study. Keep track of where you got your information from. Following web sites can be reviewed for information about mercury.

http://www.calpoison.org/public/mercury.html

http://www.pp.okstate.edu/ehs/training/mercury.htm

http://www.quackwatch.com/01QuackeryRelatedTopics/mercury.html

What is Mercury?

Mercury – known as “Hg” to chemists, is a naturally occurring element. It is a metal and conducts electricity. It is a liquid at room temperature, combines easily with other metals and expands and contracts evenly with temperature changes. Because of these properties, mercury has been used in many household, medical and industrial products.

Although mercury performs many useful functions in our workplaces and homes, it is toxic and can impair our health. Mercury acts as a poison to the central nervous system in humans. Children, especially those under the age of 6, are more susceptible to mercury poisoning. Mercury evaporates slowly at room temperature. If spilled or improperly stored, this evaporation will cause continuous contamination of the air we breathe.

How Mercury Enters the Food Chain

Mercury from manmade and natural sources mixes with rain and snow and falls into lakes and waterways. When mercury is deposited in lakes or waterways, bacteria convert it to methylmercury. Methylmercury contaminates the food chain and builds up in the tissue of fish and wildlife and humans who eat the fish.

Improper mercury disposal includes pouring it down the drain, putting it in the trash and burning it in barrels and incinerators. These improper disposal methods can elevate mercury contamination in the environment.

Fish Advisory

Picture of fishThe Connecticut Department of Public Health and the Connecticut Department of Environmental Protection have issued fish advisories that place limits on safe quantities for consumption. Pregnant women, women planning to become pregnant and children under 6 years old must be especially careful. They should not eat bass and pickerel from Dodge Pond, Lake McDonough, Silver Lake, and Lake Wyassup. All others are advised to limit consumption to one meal per month of fish except trout from these and all other freshwater waterbodies in Connecticut.

Mercury and how it is used

Mercury is a metal that occurs naturally in small amounts in the environment in several forms. Metallic mercury is a shiny, silver-white, odorless liquid. Because it remains liquid at room temperature, mercury is used in many consumer products. Mercury is used in barometers, blood pressure instruments, thermometers, and other pressure-sensing instruments. Batteries containing mercury are used in some small electronic devices. Mercury is also used in outdoor lighting, thermostats & light switches, motion picture projection and the making of some medications. If heated, mercury is a colorless, odorless gas. Source: Illinois Department of Public Health

Health issues associated with mercury exposure

Health issues caused by mercury depend on how much of it has entered the body, how it entered, length of exposure and how the body responds to it.

Mercury is harmful to both humans and animals. Children are more susceptible to mercury poisoning than adults. Exposure to even small amounts of mercury over a long period of time may cause negative health effects including damage to the brain, kidney, lungs and the developing fetus. Brief contact with high levels of mercury can cause immediate health effects including loss of appetite, fatigue, insomnia, and changes in behavior or personality. Depending on the length or degree of exposure, additional symptoms such as nausea, abdominal cramps, diarrhea, eye irritation, weight loss, skin rashes, and muscle tremors may occur.

When exposure to mercury stops, most symptoms usually go away; however, effects on the brain and nervous system may be permanent. Once mercury has entered the body, it can take months before it is eliminated, mainly through the urine and feces. Levels of mercury can be measured in blood, urine and scalp hair. These tests may help to predict possible health effects. Source: Illinois Department of Public Health

Mercury is found in a number of household products, including fever thermometers. A standard mercury fever thermometer contains about ½ gram of mercury. While this small amount of mercury does not ordinarily pose an immediate risk to the health of children, proper clean up procedures need to be implemented to ensure that the mercury does not vaporize. Mercury vapors pose a more serious threat to children’s health.

 

 

 

Chemical reactions of the elements

Reaction of mercury with air

Mercury metal reacts in air at about 350°C to form mercury(II) oxide.

2Hg(s) + O2(g) 2HgO(s) [red]

Reaction of mercury with water

Mercury does not react with water under normal conditions.

Reaction of mercury with the halogens

Mercury metal reacts with fluorine, F2, chlorine, Cl2, bromine, Br2, or iodine, I2, to form the dihalides mercury(II) fluoride, HgF2, mercury(II) chloride, HgCl2, mercury(II) bromide, HgBr2, or mercury(II) iodide, HgI2, respectively.

Hg(l) + F2(g) HgF2(s) [white]

Hg(l) + Cl2(g) HgCl2(s) [white]

Hg(l) + Br2(l) HgBr2(s) [white]

Hg(l) + I2(s) HgI2(s) [red]

Reaction of mercury with acids

Mercury does not react with non-oxidizing acids but does react with concentrated nitric acid, HNO3, or concentrated sulphuric acid, H2SO4, to form mercury(II) compounds together with nitrogen or sulphur oxides.

Mercury dissolves slowly in dilute nitric acid to form mercury(I) nitrate, mercurous nitrate, Hg2(NO3)2.

Reaction of mercury with bases
Mercury does not react with alkalis under normal conditions.

Decomposition Reactions

Essentially, decomposition reaction are the opposite of combination reactions. A compound decomposes (i.e.,”splits-up”) into two or more compounds and/or elements. For example mercury(II) oxide will, upon heating, decompose into mercury metal and oxygen:

Question/ Purpose:

The purpose of this project is to demonstrate some of the mercury applications.

Identify Variables:

When you think you know what variables may be involved, think about ways to change one at a time. If you change more than one at a time, you will not know what variable is causing your observation. Sometimes variables are linked and work together to cause something. At first, try to choose variables that you think act independently of each other.

Hypothesis:

Based on your gathered information, make an educated guess about what types of things affect the system you are working with. Identifying variables is necessary before you can make a hypothesis.

Experiment Design:

Because of many know applications of mercury, different experiments can be designed and performed using mercury. Among those experiments are:

MAKING A BAROMETER (Adult supervision required)

Equipment:

• Glass barometer tube 36″ long, closed at one end
• Small glass or beaker
• Mercury
• Ring stand with clamp
• Cardboard strip, 2″ x 10″
• Scotch or masking tape
• Yardstick

Pour the mercury into the barometer tube, filling it completely. Pour the remaining mercury into a beaker. Place a finger over the open end of the tube and invert the tube, lowering it carefully into the beaker containing the remainder of the mercury. Clamp the tube upright on the stand.

Mark a scale of inches and half inches on the cardboard, and label it from 24 to 36 inches. With the yardstick, measure the actual height of the mercury column and attach the scale to the proper spot on the tube.

Watch the day-to-day variations in the height of the mercury. Record your readings. Compare them with radio and newspaper reports of local barometric pressure conditions.

NOTE: Wear rubber gloves and be very careful that the mercury does not come in contact with any jewelry you may be wearing.

Materials and Equipment:

List of material can be extracted from the experiment.

Results of Experiment (Observation):

Experiments are often done in series. A series of experiments can be done by changing one variable a different amount each time. A series of experiments is made up of separate experimental “runs.” During each run you make a measurement of how much the variable affected the system under study. For each run, a different amount of change in the variable is used. This produces a different amount of response in the system. You measure this response, or record data, in a table for this purpose. This is considered “raw data” since it has not been processed or interpreted yet. When raw data gets processed mathematically, for example, it becomes results.

Calculations:

You may not need any calculation for this project.

Summery of Results:

Summarize what happened. This can be in the form of a table of processed numerical data, or graphs. It could also be a written statement of what occurred during experiments.

It is from calculations using recorded data that tables and graphs are made. Studying tables and graphs, we can see trends that tell us how different variables cause our observations. Based on these trends, we can draw conclusions about the system under study. These conclusions help us confirm or deny our original hypothesis. Often, mathematical equations can be made from graphs. These equations allow us to predict how a change will affect the system without the need to do additional experiments. Advanced levels of experimental science rely heavily on graphical and mathematical analysis of data. At this level, science becomes even more interesting and powerful.

Conclusion:

Using the trends in your experimental data and your experimental observations, try to answer your original questions. Is your hypothesis correct? Now is the time to pull together what happened, and assess the experiments you did.

Related Questions & Answers:

What you have learned may allow you to answer other questions. Many questions are related. Several new questions may have occurred to you while doing experiments. You may now be able to understand or verify things that you discovered when gathering information for the project. Questions lead to more questions, which lead to additional hypothesis that need to be tested.

Possible Errors:

If you did not observe anything different than what happened with your control, the variable you changed may not affect the system you are investigating. If you did not observe a consistent, reproducible trend in your series of experimental runs there may be experimental errors affecting your results. The first thing to check is how you are making your measurements. Is the measurement method questionable or unreliable? Maybe you are reading a scale incorrectly, or maybe the measuring instrument is working erratically.

If you determine that experimental errors are influencing your results, carefully rethink the design of your experiments. Review each step of the procedure to find sources of potential errors. If possible, have a scientist review the procedure with you. Sometimes the designer of an experiment can miss the obvious.

References:

List of References