Science Makes Sense-Week41:Noble metals

July 11, 2016

In many Indian households, a family’s worth/status is measured by the amount of gold or silver jewelry the women wear.  For many years, actual gold coins were used as monetary currency till other metal coins were produced.  The U.S. Treasury printed the first paper money in 1861.  By the mid 1800’s most of the trading countries wanted to standardize transactions in the booming world market.   They adopted the gold standard.  This meant that governments could redeem paper money for its value in gold.(Ref.1)

Gold,Au, silver,Ag, platinum,Pt, along with other elements  like ruthenium, rhodium,palladium, osmium, iridium, are considered to be the noble metals since they do not oxidize or react easily under normal conditions like most other elements.   These eight elements form a rectangle block in the transition metals group.  The field of physics restricts the definition to include only three elements: gold, silver and copper,Cu, because these three elements have filled electronic ‘d’ bands.  However, in chemistry, copper is known to react quite well and form a series of well-known compounds, hence the former collection of noble metals makes more sense.(Ref.2)

These noble metals make excellent catalysts , especially platinum, since they are not easily oxidized or react with other chemicals that quickly.  Since Noble metals do not react so easily, they are used to clean car exhausts besides being perfect as catalytic  agents.  They are specifically used as catalysts in the manufacture of nitric acid from ammonia. (Ref.3)

Extraction of noble metals: Some of the Noble metals like platinum, iridium and rhodium are found in mines (Check Nuggets) located in some regions all over the world.  The sponge, which is what the raw material from the mines is called, is heated and turned into grains and then big bars or ingots.  After that it is heated again and hammered, it is turned into coils that are further heated to be drawn into very thin wires.  These thin wires are weaved or knitted into fine meshes.  These meshes are used as catalysts in reactions indicated above.(Ref.3)

Other uses of Noble Metals:

Ruthenium,Ru, is used to strengthen alloys with platinum,Pt and palladium, Pd, for electroplating electrical contact materials to be corrosion-resistant, on tips of fountain pen nibs, as a catalyst to split hydrogen sulfide, H2S, and in catalytic converters in automobiles. Rhodium,Rh, is used as a 3-way catlaytic converter in industry and in the production of acetic acid, CH3COOH, from methanol, CH3OH.  It is also used in the electroplating of platinum, Pt and white gold.  Palladium,Pd, is used mainly in jewelry, dentistry, watchmaking, spark plugs for aircraft, surgical instruments.  Iridium,Ir, is a very hard metal and has many applications in industry.  Because of its great resistance to corrosion and a high melting point, it is used in specialized spark plug manufacturing, pen nibs,  as a catalyst and for electrodes.  Machinery parts like spinnerets, balances and high temperature crucibles in the laboratory are also made with iridium, Ir.   The metals, platinum, Pt, gold, Au, and silver,Ag are used as bullion metals, i.e., in making coins as well as jewelry.  Ag is used as an anti- bacterial  medicine, and Pt is used extensively as a catalyst and for electrodes. Meanwhile Au has been used for years  and years to make coins and as a currency.(Ref.4)  Osmium,Os, is used as an alloy ( 90%Pt and 10%Os) for making surgical instruments and the manufacture of pacemakers.  Osmium tetroxide, an oxide of osmium, OsO4, is used in microscopy as a stain for fatty tissue and in fingerprint detection. (Ref.5)

The noble metals group play an important role in our lives, even though they are not as reactive as other metals in the Periodic Table.  Perhaps their low reactivity makes them unique in their applications.

Activities for Middle School Teachers:

What a wealth of fields one can study here: history, geography, economics, science and several cultures!  Let students look at a map and focus on the area once known as Lydia and find out how they fashioned gold.  Where was gold concentrated in the Americas? Study history and geography as the students look at the Aztecs, the Incas and the arrival of Columbus, the conquistadores and the fight for gold.   How did the English colonials in India plunder the gold and wealth there?   Study the wealth in Europe and the Americas especially in some of the old palaces, churches in France, Austria., Germany, Spain, Central America.  Look at the timeline of how gold has been considered such a valuable asset in so many ecomomies.  How do different cultures use gold, silver and the other noble metals today?  Students who come from India can talk about how people wear gold jewelry especially during weddings and special occassions.  Use pictures and take photographs of Indian weddings if possible.

Nuggets of Information:

Sometimes mercury and rhenium are included in the list of noble metals.(Ref.2)

By 560, the Lydians ,in the region between the Mediterranean, Aegean and Black Seas where modern Turkey is situated, succeeded in separating silver from gold and created the first gold coins.(Refs.2,6)

During the days of exploration, the wealthiest country had the most gold.  This explains the reasons why countries like Spain, Portugal and England vied with each other to send explorers like Columbus and others to places like the New World ( the Americas) and the east in search of gold.(Ref.2)

The gold rush of 1948-49 in California initiated the unification of the western part of the United States of America.(Ref.2)

Sometimes the people who work in the manufacture of noble metals from mines use special brushes to recover noble metals from their shoes.  This is called sponge.  One ounce of sponge is obtained from 10-40 tons of rock.(Ref.3)

Noble metals are found in mines that are in South Africa, Canada, Russia  and Zimbabwe. Processing of platinum takes 6 weeks while rhodium takes almost 6 months.(Ref.3)

Palladium is used for blood sugar testing strips and is one of the 4 bullions used by ISO (International Standards Organization) for currency codes.

Rhodium is used as a filter in mammography systems, neutron detectors in combustion systems. Ruthenium is used as a biological stain; staining pectin and nucleic acids.(Ref.4)  A biological stain is used to highlight biological tissue details. (Ref.7)  

When crude platinum was dissolved in aqua regia (a mixture of concentrated nitric and hydrochloric acid: HNO3+HCl) a black metallic powder was formed.  In 1803, the English chemist Tennant recovered  osmium and iridium from this mixture.   The name ‘osmium’ comes from the Greek word ‘osme’ which means unpleasant odor. Os and Ir are very dense; Os is the densest element known.   OsO4, osmium tetroxide is highly toxic and causes lung, skin and eye damage.(Ref.5)

References:

1.http://useconomy.about.com/od/monetarypolicy/p/gold_history.htm

2.http://chemistry.about.com/od/metalsalloys/a/Noble-Metals.htm

3.https://www.bing.com/videos/search?q=where+do+you+find+ruthenium%2c+rhodium%2c+osmium%3f&view=detail&mid=6B2D091A3581A6CE0D986B2D091A3581A6CE0D98&FORM=VIRE

4.http://www.ehow.com/list_6003330_uses-noble-metals.html

5.http://www.chemicool.com/elements/osmium.htm

6.http://www.kidspast.com/world-history/0045-lydians.php

7.http://www.organicdye.com/dyes/biological-stains/

 

 

 

Science Makes Sense-Chemistry and Social Justice-Week40: Fats, salt and sugar: are we eating too much?

June 28, 2016

Two famous Michaels, Michael Pollan and Michael Moss lament the fact that we are cooking less and relying on fast foods.  In their books, ” Omnivore’s Dilemma”,  “Cooked”( Michael Pollan) and “Salt, Sugar, Fat”( Michael Moss), they outline how food is delivered and how home cooking is being sidelined in many houses.(Refs.1,2,3)

I was fortunate to grow up in a home where my parents cooked most of the time.  Even when I started living away in my own home, I did cook almost every day and going out was relegated to once a month or every two months.  These days, I prefer a simple meal at home.  However, most working people eat at odd times and sometimes order in, since they come home tired to plan and prepare a meal.  This has led to more consumption of oily foods, laced with extra salt and desserts/breakfast foods loaded with fat and sugar.  It is also true that the availability of fresh fruits and vegetables at reasonable prices is not as easy in poorer neighborhoods where fast food restaurants are seen more often.  Today we shall look at the prevalence of fast and convenience foods, who tends to buy them and what measures are being taken in certain neighborhoods to encourage healthy eating. We shall look at the additives added in convenience and fast food as well and revisit the saturated, unsaturated as well as trans fats discussion.

First we will look at the term’processed food’.    Processed food is different from home-cooked food in the sense that additives are added to preserve shelf life.  The simplest processed food we see in the supermarket is canned soup.  What does it contain?   A lot of salt is added to preserve it and other additives are also added.  In the inner linings of food cans you find BPA, (Ref.4) which is chemically a bis phenol derivative where two phenol rings are connected via three carbon chains. (Ref.5)  BPA has been known to leach into the soup itself and cause obesity as well as breast and prostate cancers; it has even caused behavioral problems in young girls.  Salt as we know it is sodium chloride, NaCl, and high amounts of sodium ions is known to be responsible for heart attacks and  has lead to strokes (Ref.4)

Besides the additives indicated above let us look at food flavorings and colors, preservatives, chemicals added to change the texture of processed foods.  Among artificial flavoring, butyl alcohol,C4H9OH is one chemical that is added to mimic flavors of naturally occurring foods like butter, fruits.  There are serious health problems caused by too much consumption of this food flavoring.  Artificial sweeteners like aspartame, splenda are used by people with diabetes.  We know that regular sugar causes obesity and heart problems, but the artificial sweeteners consumed continuously causes headaches, seizures and even hallucinations. Benzoic acid(C6H5COOH)  is used  as a preservative in certain pickles, jams and fruit juices and this can cause asthma attacks, hyperactivity in children and neurological disorders.   Artificial colors like Blue 1,2 and some yellows and reds are known to cause certain kinds of cancers.  Vegetable oils that are brominated, ie contain Br, (bromine) a halogen,causes tremors and headaches.  (The Br is added as an emulsifier to prevent the oil from separating out). Carageenan, a  familiar thickener found in ice-creams, jellies has been found to form ulcers and cancers in animal studies.  High fructose corn syrup or HFCS  a fructose polysaccharide from corn, has been known to cause obesity and elevated cholesterol.  We already know the dangers of saturated fats ( less or no double bonds in the fatty acids that produce the oils/fats by esterification) but trans fats are even worse.  This is produced by forcing hydrogen gas over vegetable fats at high pressure and causing -COOH in trans positions hence the name’trans-fats‘.  Many fast food, especially fried foods contain trans-fats and the greater consumption has let to obesity among children and heart diseases.  Nitrates,nitrites of sodium(Na2NO3,Na2NO2) are used extensively in processed meat and is known to be a carcinogen.  And finally, sulfur dioxide, SO2, is added to dried fruits and is responsible for migraine headaches and asthma attacks.(Ref.6)

This list is not exhaustive, there are many more additives, fillers, flavors and colors used in processed foods that are not healthy at all.  But one would imagine that the above chemicals are enough for most of us to start cooking/ eating at home making simple, healthy meals while we know what is going inside our bodies.

But the switch is not easy and between the unhealthy but appetizing messages from the advertising industry, the convenience of ordering take-out and the higher prices of good healthy foods makes it very challenging for consumers to eat a balanced, nutritious meal everyday. (look at Activities and Nuggets)

Activities for Middle School Teachers:

Teachers can encourage students to map out their neighborhoods and actually find out what kind of food stores are available close by.  Then  each student can bring a can of food from home and find out what are the ingredients in them.    What chemicals are there in the additives? Why are they added to the food?  Is it made close by or comes from a far off place?  The teacher can then link geography with that particular can of food and ask students to see why that can of food  had to come from so far away.   The teacher can  introduce words like “locavore”  and”CAFO”and explain the meaning.  What alternatives would make sense? How did their grandparents obtain their daily food?  They could interview each other and find out how often they eat at fast food places, whether their family or friends have a vegetable garden in the summer and where they buy their groceries.  Does culture, where they come from influence what they eat?  Are students willing to try foods from different countries?  What limits them ?  Does having more money make people eat better food?   Does food advertising affect their daily food habits? Why or why not?

Students can also do research on where the food is grown, how it is grown and the difference between organic and regular food, GMO and non-GMO food, and humane or inhumane ways of raising chickens,animals for food consumption and who can afford which kind of food.

Nuggets of Information:

Most artificial flavorings have been banned in the European Union.(Ref.6)

“Food First ” is a book written by Fraces Moore Lappe where she encourages people to understand the politics of food and why growing your own food is the best way to control what one can eat.(Ref.7)  It is also necessary not to be a passive consumer but understand that supermarkets encourage us to consume high fat, high sugar products by simple things like arrangement of cereals / cans/ processed foods in an aisle.(Ref.8)

Morgan Spurlock in the movie”Supersize Me” makes us think twice about eating at fast food places too often.  He actually did an experiment on himself by eating fast food day and night for a month at McDonald’s and noticed how adversely it affected his own health!(Ref.9)

CAFO, or concentrated animal feeding operations or factory farms, keep animals in small confined spaces to feed and take care of them before butchering them for meat.  There have been enough studies done to show that the process is inhumane and unhealthy.(Ref.10)

References:

1. Pollan, Michael, Omnivore’s Dilemma (Penguin Press,2006)

2.Pollan, Michael, Cooked (Penguin Press,2013)

3.Moss, Michael, Salt, Sugar, Fat (Random House,2013)

4.http://www.rodalewellness.com/health/canned-soup

5.http://www.chemspider.com/Chemical-Structure.6371.html

6.http://peopleforethicalliving.com/health-and-fitness/food-choices-nutrition/dangerous-food-additives/

7.Lappe, Frances Moore,Food First (Souvenir Press Ltd.,1980)

8.http://www.regainedwellness.com/supermarket-psychology/

9. Supersize Me! the movie with Morgan Spurlock

10.Foer,Jonathan Safran ,Eating Animals (Little Brown and Co.,2009)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Science Makes Sense- Week 39:Organic Chemistry,Lipids, oils and fats

June 21, 2016

Almost every child in America gets its first taste of fast food with a packet of fries: Mmmm…so good! As children we grew up with occasional treats of fried potatoes that were irresistible. When I first landed in the U.S.,I always bought a bag of potato chips to remind me of fried food in India.
Oil has a unique way of adding flavor to any food. Today let us look at the chemistry of oils. Lipids are biological chemicals that do not dissolve in water.(Ref.1) These are a group of fat soluble compounds found in the tissues of plants and animals. Fats and oils are a sub-set or subgroup of lipids and are basically storehouses of energy. But lipids play an important role in the formation of cellular membranes,cellular signaling, nutrient functions with relationships to vitamins A,D,E,and K as well as being storehouses of energy. Furthermore, lipids are complex molecules with carbon, hydrogen and oxygen as well as nitrogen and sulfur and other small constituents.(Ref.2)
Fats and oils share a common molecular structure; fats are solids at room temperature, oils are liquids. What is the molecular structure?
They are esters of tri-alcohols, i.e., three -OH groups,also called glycerols,hence fats and oils are also commonly known as glycerides.  An ester has the H in the -OH group replaced by  a carbon chain and since there are 3 -OH groups there could be three different carbon chains called R1, R2 and R3 respectively.(Ref.1)  Remember that an ester in organic chemistry is like a salt in inorganic chemistry .  A salt is the neutralization reaction between a base/alkali and an inorganic acid, whereas an ester is a similar kind of neutralization reaction between an alcohol and an organic acid.   The more accurate name would be Triacylglycerols.   Hydrolysis (or reaction with water) of fats leads to glycerols and fatty acids.(Ref.1)

Triglyceride molecules contain carbon and hydrogen molecules and usually six oxygen atoms in every molecule.  This makes them highly reduced or unoxidized.  They resemble the hydrocarbons in petroleum and are good sources of fuel.  In fact the normal human body stores fats as fuel/ energy for several weeks’ survival.  Plants too do the same thing and this allows them to deal with unpredictable sources of food supply.(Ref.1)

A triglyceride is called a fat if it is a solid at 25°C, if it remains a liquid at this temperature, it is termed an oil.  The difference in melting point reflects the difference in the degree of unsaturation and number of carbon atoms in the original fatty acids that resulted in the triglyceride. (Ref.3)

Pure fats and oils are colorless,odorless and tasteless.  They are lighter than water, their densities are usually around 0.8gm/cc. They are poor conductors of heat and electricity and hence are excellent insulators for the body, slowing the loss of heat through the skin.(Ref.3)

The double bonds in fats and oils can undergo hydrogenation as well as oxidation.  The hydrogenation of oils is used commercially to produce margarine.  Most fats are obtained from animal sources whereas most plant sources produce oils.  Saturated fats/oils are derived from saturated fatty acids ( less or no double bonds) while unsaturated fats/oils are derived from unsaturated fatty acids ( more double bonds).  The high consumption of saturated fats, along with high cholesterol leads to increased risks of heart disease..(Ref.3)

The study of lipids, fats and oils indicates how necessary they are in the function and maintenance of our body’s functions.  However, too much of saturated fats and oils consumption today, especially because of the  fast food industry and in the changes in our lives has led to all kinds of medical problems.  We shall look closer at this topic next week.

Here is a small table to illustrate the predominance of saturated fatty acids in fats and more of the unsaturated fatty acids in oils:.(Ref.4)

Animal fats   Saturated acid(%)             Unsaturated Acids(%)

C10 &less     C12     C14     C16    C18        C18(a)C18(b) C18(c)

Butter     15         2          11        13        9            27      4         1

Lard             –        –             1         27     15          48    6          2

Plant oils               Saturated acid(%)           Unsaturated acids(%)

Coconut     –       50           18        8     2             6      1           –

Corn           –        –             1        10      3            50     34        –

Olive           –         –           –          7        2             85       5       –

Safflower   –         –            –         3        3             19     76       7

Activities for Middle School Teachers:

Let students make models of different fatty acids and triglycerides. Students need to research the reasons why unsaturated fats are not solids even though there are more double bonds here and the molecule ( fatty acid or corresponding triglyceride) may be dense and therefore could become a solid.  The Van der Waals weak intermolecular forces are stronger when you have long chain straight molecules; this happens with saturated fat molecules.  On the other hand, the presence of double bonds causes kinks in the structures making them non-planar.  Students will find a relationship between melting points and straight-chain versus non-planar structures. Students can plot a graph and present results.(Ref.5)

Nuggets of Information:

When all three hydroxyl groups (-OH) groups in the glycerol molecule are esterified with the same fatty acid, the resulting glyceride is called a simple glyceride.  In nature, you never see a simple glyceride, since the esterification in nature involves several different fatty acids.  That is because naturally occurring acids are a mixture of several fatty acids.(Ref.3)  No single formula can be written to represent naturally occurring fats and oils.  They may be derived from several different fatty acids.  Palmitic acid is the most abundant saturated fatty acid and oleic acid is the most abundant unsaturated fatty acid.(Ref.3)

Even though most fats are derived from animals, the exception is fish oil; triglycerides from fish are found as oils..(Ref.4)

Seeds contain a lot of oil/fats; the stored energy helps seedlings during germination.  later, they have solar energy available for photosynthesis.(Ref.3)

Hydrolysis of fats and oils in the presence of a base produces soap and the process is called saponification.(Ref.3)

Lipids can be  further classified as fats, oils, phospholipids, waxes, sterols .(Ref.4) Phospholipids  are a class of lipids similar to triglycerlides , where the fatty acid from which it is derived contains a phosphorus atom; they are present in cell membranes. Sterols are a class of lipids with structure similar to cholesterol.(Ref.6)  Cholesterol comes under the umbrella of steroids which have a carbon backbone with four fused ring-like strucures and a hydoxyl group (-OH).  Waxes are esters of a long-chain fatty alcohol and a fatty acid.  Many plants and fruits have a waxy coating to prevent water loss.(Ref.7)

Ear wax is composed of phospholipids and esters of cholesterol!(Ref.7)

References:

1.http://scifun.chem.wisc.edu/chemweek/pdf/Fats&Oils.pdf

2.http://www.differencebetween.info/difference-between-lipids-and-fats

3.http://chemwiki.ucdavis.edu/Textbook_Maps/General_Chemistry_Textbook_Maps/Map%3A_The_Basics_of_GOB_Chemistry_(Ball_et_al.)/17%3A_Lipids/17.2_Fats_and_Oils

4.http://www2.chemistry.msu.edu/faculty/reusch/VirtTxtJml/lipids.htm

5.http://chemistry.stackexchange.com/questions/4058/saturated-vs-unsaturated-fats-structure-in-relation-to-room-temperature-state

6.https://quizlet.com/94654736/chapter-5-lipids-fats-phospholipids-and-sterols-flash-cards/

7.http://biology.about.com/od/molecularbiology/ss/lipids.htm

 

 

 

 

 

  

Science Makes Sense Week 38:Noble gases

June 13, 2016

I remember when I was young, I liked stretching on a black sofa almost upside-down and reading a book. My mother would come and implore me to go out and I would be oblivious to her presence. “Why aren’t you reacting? It is as if you are in another world!”, she would remark in dismay.
Sometimes, when I look at the last group in the Periodic Table, the Noble Gases, I wonder if they too belong in another world. Helium,He, neon, Ne, argon, Ar, krypton,Kr, xenon, Xe and radon, Rn are the six common noble gases. All these are obviously gases and the outer electronic structure is a stable octet, which is really a ns2 np6 configuration, where n=2 through 6. The exception is helium, which has a stable duplet or 1s2 structure.
One has already seen that the alkali and alkaline- earth elements try to lose one or two electrons to achieve the stable noble gas structure. In addition we have seen that the halogens gain an electron to have the outer stable electronic structure of noble gases. In fact, almost all elements in the periodic table gain or lose electrons during a chemical reaction to get to the stable electronic structure of these noble or inert gases. This also implies that the last group elements are not reactive. Now is that really a fact?
Till the early 60’s, scientists were talking about the stable octet/duplet rule to justify the non-reactive nature of these gases. Initially it was called Group 0 for this reason. In 1962 and 1963,scientists observed that some of the noble gases,like radon, krypton and xenon form different flourides. In addition, in 2006, scientists in Dubna, Russia, announced that the element 118, the next noble gas, was synthesized in 2002 and 2005 in a cyclotron.(Ref.1) A cyclotron is a high particle accelerator where subatomic particles like protons and electrons are in a magnetic and electrical field and can collide at high speeds with each other.(Ref.2)
Hence there are really 7 noble gases present and since some of them are not completely non-reactive, the noble gases group is now called Group 18 and not Group 0.(Ref.1)
The noble gases are all colorless, odorless, tasteless, non-flammable gases. They also happen to be mono-atomic gases, ie, they exist as individual atoms rather than di- or poly- atomic molecules.(Ref.3) They were originally called inert or rare gases. They are neither inert(since we know some of them react with flourine to form compounds) nor rare, because several of them are found in abundance on earth.(Ref.1) Yet the word’noble’ is appropriate, since certain elements like gold or platinum are also considered ‘noble metals’ because of their reluctance to undergo chemical reactions easily.(Ref.1)
How abundant are these noble gases? It is noted that their abundance decreases with increase in atomic weight, with He being the most abundant while there are only three molecules of element 118! Most of the noble gases are present in the earth’s atmosphere, except for helium, radon and are recovered from the air by obtaining them as liquids and conducting fractional distillation to separate them.(Ref.1) (Fractional distillation is a technique whereby different liquids can be distilled/condensed using differences in their boiling points, to collect each substance separately.)
Actually both radon and even helium are by-products of radioactive decay. After the discovery of radium by the Curies, German physicist became fascinated with radium and discovered a gas that it emitted and he called it ‘radium emitting; he discovered the new element, radon. The breakdown of radium as well as uranium can lead to the production of helium ions as well.(Ref.3)
The noble gases are used in many daily and specialized applications. Helium as we already know has been used in the filling of balloons, for large airships and for children. Helium is also used by divers not for buoyancy but to prevent “the bends” a condition when nitrogen bubbles in the blood as a diver comes up to the surface. Helium is extensively used in the field of cryogenics which is low-temperature science. Neon is best known for its use in neon signs, neon glow lamps are used to indicate on/off signs in electronic instrument panels and in early televisions. Even though radon is considered a hazard it has its uses in earthquake detection, leaks, measuring flow rates. Paleontologists, who study the distant past as well as geologists use argon dating to study volcanic layers, fossils etc. Krypton is mixed with argon in the manufacture of windows with high thermal efficiency, used in lasers as well as halogen headlights. Along with xenon, especially because of its lower cost, krypton has been used as a fuel in space.
(Ref.3)

As one can see, these noble gases are not so quiet and inert as they seem.
Activities for Middle School Teachers:
Have a discussion with students about how certain words like ‘inert’, ‘rare’ to describe the Group 18 gases is really not accurate. Look at the history of the ‘phlogiston’ theory and how the burning/oxidation theory was modified with further experiments in science. Look at the history of the atomic models and see how those models evolved with time and more knowledge. How did the invention of new instruments in the laboratory aid these developments? Compare the evolution of ideas in chemistry, physics with say, social sciences and psychology.
Nuggets of Information:
In 1868, a French astronomer named Pierre Janssen (1824-1907)came to India to observe a total solar eclipse. Using a spectroscope, an instrument for analyzing the spectrum of light emitted by an object, Janssen was able to show a yellow line in the spectrum, never seen before, which seemed to indicate the presence of a previously undiscovered element. He called it “helium” after the Greek god Helios, or Apollo, whom the ancients associated with the Sun.(Ref.3)
Helium is remarkable since it only liquefies close to absolute zero(-272 degrees celcius); that makes it very difficult to liquefy from air.(Ref.3)
Almost all the noble gases have derived their names from the Greek language. Neon comes from the word ‘neos’ which means new,argon from ‘argos'(inactive), krypton from kryptos,(hidden) and xenon from the word ‘stranger’.(Ref.3)
Superman’s kryptonite is an imaginary substance and has no relationship with the noble gas krypton.(Ref.3)
The discovery of radon starting with the element radium was the first clear proof of one element being transformed to another element through radioactive decay. (Ref.3)
Within the atmosphere,, argon is considered the most ‘abundant’ of these gases, about 0.93%.(Ref.3)
Until 1988, most Americans had no knowledge of the existence of radon, when the EPA(Environmental Protection Agency) released a report indicating the harmful effects of radon in homes. From the 80s through the 90s radon detector sales boomed; even today when a house is sold, radon levels need to be checked. This is especially needed if a house has been weather-sealed to improve heating and cooling.(Ref.3)
Chinese scientists made an interesting discovery in the 1960s. Radon levels in groundwater increased significantly before an earthquake. These scientists monitor radon levels to predict earthquakes.(Ref.3)
References:
1.http://www.britannica.com
2.http://www.thefreedictionary.com/cyclotron
3.encyclopedia.com/topic/Noble_gases.aspx

Science Makes Sense-Week 37: The alkaline earth metals

May 17, 2016

My grandmother was very particular that all the grandchildren who came to visit her had milk at night. She would stand with a big warm container of milk and insist that we all had a small glass before we went to bed. My younger sister hated this white liquid and would swallow it with great difficulty. Even now she dislikes the taste of milk but gets her calcium from plenty of yogurt and dietary supplements.
Calcium,Ca, is one of the alkaline-earth metals along with Beryllium,Be, Magnesium,Mg,Strontium,Sr, Barium,Ba and Radium, Ra. (Radium was covered last week) All are metals and form Group 2, next to the Group 1 alkali-metals in the Periodic Table. Like the alkali-metals, they are soft, silvery-white metals, reactive (but not as reactive as the alkali-metals) and never found as an element in the natural state. And again, like them, they glow with characteristic colors and are distinguished by the flame test. Unlike the alkali-metals which have 1 electron in the ‘s’ shell, they have two electrons in the ‘s’ shell.(Ref.1)
Some of the alkaline-earth metals except radium and beryllium were discovered by the English Chemist, Sir Humphrey Davy in the early part of the 19th century. Around this period, Sir Davy also discovered two of the alkali-earth metals, potassium and sodium.(Ref.1)
The alkaline-earth metals react easily with water to release hydrogen gas and form the metal hydroxide. Many of them react with oxygen to form oxides. In nature they are usually found as sulfates and carbonates.(Ref.1)
The most abundant of these metals is calcium, Ca. It is the fifth most abundant element in the earth’s crust as well as in the human body. Magnesium, Mg is the seventh most abundant element in the human body, whereas Ba, Be nor Ra, St are found in the body, since the first two are poisonous while radium is radioactive; meanwhile strontium is only present as 360 ppm on the earth’s crust.(Ref.1)
Beryllium is used in the health-care industry, (besides being found in precious stones)in X-ray tubes as well as in alloys for specialized electrical connections and for high-temperature uses.
Besides magnesium being important as a digestive aid and formerly used for asbestos, today it is used in the manufacture of fertilizers. Because of its property to burn in oxygen with a brilliant flame,in World War 1, magnesium was used as flares, tracer bullets and incendiary bombs. Later in World War 2, it was used to build aircraft and military equipment. Today it is used with other metals to manufacture catcher’s masks, skis, race cars and even horseshoes.(Ref.1)
Calcium has been used in buildings from ancient times. Steel, glass, paper and metallurgical industries use slaked lime(calcium hydroxide, Ca(OH)2). Acetylene used for welding is made by reacting calcium carbide(CaC2) with water. Calcium compounds are also used as a bleach, fertilizer and sometimes to melt ice on roads.
Even though strontium is not as abundantly available it still has several uses. Like magnesium, it is used for flares, tracer bullets and also for fireworks- having a brilliant crimson color. It is also used in color television picture tubes, to refine zinc and combined with iron, strontium is used to make magnets.(Ref.1)
Barium compounds are used extensively in health care applications: in enemas and also to coat inner linings of intestines so doctors can examine the patients’ digestive system.(Ref.1)
The alkaline-earth elements are used in a wide variety of ways; they are not just known for calcium and strong bones.
Activities for Middle School Teachers:
Study the boiling and melting points of the alkaline- earth elements. Is there a correlation between them and their atomic numbers as in the case of alkali-metals?
Helium,, He, has two electrons in its outermost ‘s’ shell, why then does it not behave like an alkaline-earth metal? Let the students discuss this with the teacher.
Nuggets of Information:
Beryllium is found in emeralds and aquamarines as a compound of beryllium and alumino-silicate and is called beryl.(Ref.1)
Magnesium is found as dolomite or magnesite which are carbonates of magnesium, MgCO3. (Ref.1)
Calcium is found mostly as limestone and as dolomite (calcium carbonate, CaCO3) and also as gypsum(calcium sulfate, CaSO4)
Strontium was initially discovered by Adair Crawford, an Irish Chemist in the late 18th century in witherite; it is also found in strontianite(strontium carbonate, SrCO3) and in celestite( strontium sulfate,SrSO4)(Ref.2)
Barium is found as barite(BaSO4,barium sulfate) or witherite(BaCO3,barium carbonate)(Ref.3)
Magnesium sulfate, also known as Epsom salts has been long known for their medicinal value,mainly in Epsom salts springs. It has also been used for the treatment of eclampsia, a condition that causes seizures in pregnant women.(Ref.1)
Salts of magnesium are used as a powerful laxative(Ref.1) but magnesium hydroxide,Mg(OH)2 also known an milk of magnesia is the preferred laxative.(Ref.4)
One of the most controversial uses of magnesium has been in asbestos, as a fire retardant. It is a silicate of magnesium with the formula Mg3Si2O5(OH)4. This had been used for commercial purposes 95% of the time.(Ref.5) For years it was used as a flame-retardant till it was found to be cancer-causing and had to be removed from many buildings. In spite of this, magnesium as an element is important in the health of living organisms.(Ref.1)
Magnesium plays a critical role in chlorophyll, the green pigment in plants that gets its energy from sunlight.(Ref.1)
More than magnesium, calcium is vital for living beings and is present in leaves, teeth, bones, shells and coral.(Ref.1)
We all know that calcium is essential for bone-building but it also plays an integral part in almost every cell in the body especially in the growth of muscles, the nervous system as well as the heart.(Ref.6)
Osteoporosis is caused by a loss in bone density and can be prevented by eating foods high in calcium like green vegetables and dairy products.(Ref.1)
An isotope of strontium, Sr 90, is radioactive and is a by-product of nuclear testing from the ’40’s. Once, during testing, this isotope fell to earth, coated grass and was ingested by cows. The milk from these cows was drunk by many children when the Sr 90 got into their teeth and gums causing many health problems. In the 60’s atmospheric nuclear testing was stopped. Strontium 90 affects production of red blood cells and could lead to death.(Ref.1)
Prior to receiving X-rays, patients drink a chalky barium sulfate,BaSO4 solution which absorbs radiation and adds contrast to the image.(Ref.1)
References:
1.http://www.encyclopedia.com/topic/alkaline-earth_metals.aspx
2.http://education.jlab.org/itselemental/ele038.html
3.http://education.jlab.org/itselemental/ele056.html
4.https://www.medicines.org.uk/emc/medicine/17293
5.http://www.britannica.com/science/asbestos-mineral
6..http://www.helpguide.org/articles/healthy-eating/calcium-and-your-bones.htm

Science Makes Sense-Week 36: Chemistry and Social Justice-radiation, radium girls.

May 9, 2016

I remember when I was six or seven, my uncle came to visit us in the evening when we had a power cut in India and had no electricity. Everything turned pitch dark but I could see my uncle’s watch gleaming green in the dark! “Why is that happening? Do you have a magic watch?” I exclaimed. ” No magic, it is a glow-in-the-dark watch,” he responded. I was fascinated and learned years later that it was a radium watch. The dials had been painted with a salt containing radium.
Today we shall look closely at the discovery and use of one of the radioactive elements, radium (mention others in nuggets) and the terrible results of exposure due to ignorance and careless/negligent planning.
Radium was discovered by Pierre and Marie Curie in 1897 along with Polonium.(Ref.1) Pierre and Marie Curie were unaware of the dangers in the late 19th century/ early 20th century about nuclear reactions.
Most chemical reactions occur through transference/sharing of electrons, those very tiny particles that circle far away from the nucleus of an atom of any element. The nucleus is not touched in such reactions; however by the end of the 19th century, scientists were entering the realm of nuclear reactions. The nucleus is where the protons and neutrons are situated. The energy released when the nucleus is attacked, is several times that of a chemical reaction. Such attacks can be man-made as in nuclear reactors, and the explosion of atomic bombs, but radioactive elements that naturally decay can also cause nuclear reactions.
In fact Henri Becquerel was the first to observe mysterious radiation in uranium compounds and Maria and Pierre Curie did measurements on the amount of radiation emitted.(Ref.1) It is important to note that elements like technitium,Tc, prometheium, Pm as well as elements starting with polonium Po, all the way to the end of the Periodic Table exhibit radioactivity. In other words all the elements from atomic number 84 to atomic number 105 are radioactive, besides technitium and prometheium. Some of these elements are not too stable having very short half-lives.(Ref.2,3) Half life for an element is the time needed for half the mass of the element to decay.
The radioactive decay of elements leads to three kinds of ionizing radiation: alpha and beta particles as well as gamma radiation. Alpha particles consist of a pair of protons and neutrons, viz., it is a Helium ion. This is the least dangerous as far as radiation effects go, since they do not penetrate very deeply into clothing or skin. However, once ingested or inhaled through water or food sources, they could become carcinogenic and ultimately lead to lung cancer and other cancers. Beta particles are electrons that move very quickly; being 8000 times smaller than an alpha particle, this allows them to penetrate clothing and skin very easily. External exposure leads to burns and tissue damage and ingested/inhaled through water/food contamination could lead to serious health problems. Gamma rays are the most dangerous, these are fast-moving photons with no mass , passing easily through all body tissues and bone marrow causing extensive damage to the body and death based on amount/duration of exposure.(Ref.4)
While Marie and Pierre Curie may have been ignorant of the dangers of radium’s radioactivity, years later, many women were dangerously exposed to radium in U.S.factories where they were making radium watches and clocks. Referred to as the “radium girls” in Waterbury,Connecticut, Orange,New Jersey and in Ottawa, Illinois, young girls worked in factories and painted radium mixed as a paint with zinc sulfide, on dials of watches and clocks.(Ref.5) The managers, wanted them to lick the brushes so they were pointed to do the fine painting on the dials. Some of these girls even painted their buttons and finger nails to glow in the dark unaware of the terrible consequences. Initially because of ingesting alpha particles from the radioactive radium, they had terrible pains near the teeth and jaw, but eventually developed swelling and total destruction of the jaw and finally death in some cases. In Orange, new Jersey, 4 dial painters died and 8 were very ill. Dial painters there filed a suit in March of 1925 and following that workers no longer used their mouths to lick and point the brushes, they started wearing rubber gloves and use fume hoods after 1927. No more cases of cancers in dial painters were officially blamed on radiation. But the damage had been done.(Ref.5,6,7)
Years later, the suffering of the Radium girls led to safety measures for World War II atomic bomb workers.(Ref.5) Aah! But at what cost??
Activities for Middle School Teachers:
Teachers need to discuss how loosely and incorrectly certain words are used in daily life. The most common errors are made when the word ‘chemical’or ‘radiation’ is used, for example. All chemicals, radiation are considered harmful whereas water is also a chemical and electromagnetic radiation encompasses visible light. Let students research these words in science and understand the variation in meaning depending on context. Also, let students find other words in science that are mis-understood or partially explained by the non-scientific community.
Teachers should collaborate with Language Arts teachers and see if the word ‘synecdoche’ could be used to describe the incorrect usage of certain scientific words. (This word is a part of speech akin to a metaphor or simile; it means when a word is used to describe part of what it actually means)
Nuggets of Information:
Marie Curie’s notebooks and even her cookbook are so radioactively charged that they can only be viewed through lead screens today.(Ref.8)
Henri Becquerel received a burn carrying radium-rich barium chloride in his waist-pocket. Pierre Curie suggested that radium could be used for cancer therapy and in the 20’s it was used to treat some forms of skin cancer. In fact radium was touted as a cure for hypertension, diabetic pain, arthritis, gout and even for tuberculosis of the lung. Today, however radium is not used for any of this, but some research is underway to study its use to relieve intractable pain.(Ref.9)
Because of prolonged exposure to uranium, polonium and especially radium, Marie Curie succumbed to anemia related to radiation in bone marrow.(Ref.4)
The Geiger Counter was invented in 1928 and is used to measure radioactivity levels in many elements.(Ref.9)
It is important to note that all forms of radiation are not harmful to humans; e.g., electromagnetic radiation includes visible light. Also many man-made products like televisions,smart phones, microwave ovens emit radiation that are not dangerous and the danger varies with strength and length of exposure.(Ref.4)
There were 30 women in Connecticut, 35 women in Illinois and 41 women in New Jersey who died because of being dial painters (Radium Girls) in the 1920’s.(Ref.5)
Alexander Litvinenko, a former KGB officer died 3 weeks after ingesting a cup of tea containing Polonium 210.(Ref.8)
References:
1.http://chemistry.mtu.edu/~pcharles/SCIHISTORY/Marie_Curie.html
2.http://periodictable.com/Elements/Radioactive/
3.http://chemistry.about.com/od/nuclearchemistry/a/List-Of-Radioactive-Elements.htm
4.http://science.howstuffworks.com/radiation-sickness1.htm
5.http://www.waterburyobserver.org/node/586
6.Clark, Claudia, Radium Girls,(University of North Carolina Press, 1997)
7.Mullner, Ross, Deadly Glow,( American Public Health Association, 1999)
8.http://listverse.com/2010/03/25/10-famous-incidences-of-death-by-radiation/
9.http://www.rsc.org/images/Dronsfield_tcm18-200827.pdf

Science Makes Sense-Week35:Organic Chemistry,Benzenoid aromatic compounds

May 2, 2016

Every year my mother would clean her silk saris by washing them in mild soap, getting them ironed and stack them in the cupboard with a few moth balls. So every time I would open the cupboard to wear her saris I would smell the odor of moth balls and hope it did not cling to me! Moth balls originally contained naphthalene which is a benzenoid compound and we shall look at a few of these today.
Benzenoid compounds contain the benzene ring and last time we had a chance to look at the simplest of these, benzene. The structure of benzene was discovered almost simultaneously by Loschmidt and Kekule around the mid-19th century,(both German scientists) as a six-membered cyclic hydrocarbon containing 6 carbon and 6 hydrogen atoms with alternating double bonds. But it was Kekule who modified the structure to one where the oscillation of the double bonds gave two equivalent structures in rapid equilibrium. Then in 1931, Linus Pauling suggested that benzene had a single structure that was a resonance hybrid of the two Kekule structures.(Ref.1)
Benzene is a colorless volatile liquid with a characteristic strong odor and is the starting point for the manufacture of many aromatic compounds including aniline, phenols.(Ref.1)
Modern bonding models (valence bonding and molecular orbital theory) explain the stability of the benzene due to the delocalization of the six electrons. This delocalization refers to the attraction of an electron by all six carbon atoms instead of one or two, making benzene very stable. Unlike other unsaturated hydrocarbons, the hydrogenation and oxidation of benzene is a slow process. Most reactions of benzene are electrophilic aromatic substitution where the ring is intact and replacement of hydrogen occurs. Such reactions are important in forming derivatives of benzene.(Ref.1)
Benzene is present/manufactured in oil refineries, rubber and shoe manufacturing as well as in gas stations and firefighting.(Ref.2). Benzene has been documented as a cancer-causing agent and the results of exposure are mentioned in Nuggets.
The next aromatic compound we will study is toluene, also known as methyl benzene where one of the hydrogen atoms is replaced by a methyl(CH3)group. The odor is similar to benzene and it is usually a stable compound unless subjected to high temperatures. It is one of the by-products of gasoline production, but most of the benzene is manufactured starting with toluene. Toluene is used in the manufacture of adhesives, rubber, laboratory paints, pesticides and pharmaceuticals.(Ref.3)
The third set of aromatic compounds are called phenols. When a hydroxyl group, -OH group is attached to a carbon atom of a benzenoid ring, the compound is called a phenol. Phenols are similar to alcohols; however the hydrogen bond is stronger so they are more soluble in water than alcohols and have a higher boiling point. They are usually colorless liquids or white solids and are toxic and caustic. Household products that contain phenols include disinfectants and mouthwash. In industry, phenol is the starting point for plastics, explosives,photography, dyes and aspirin.(Ref.4)
Finally we will look at the chemical composition of moth balls, another benzenoid compound. Today we use dichloro-benzene , but years ago naphthalene was used in the manufacture of moth balls. 2 fused rings of benzene comprise naphthalene with the formula C10H8. Naphthalene is a white, solid crystal and has a strong odor of coal tar. It can undergo electrophilic aromatic substitution. It can be hydrogenated partially to form 1,2,3,4 tetra hydro-naphthalene or completely to form decalin, C10H18. Both are used as low volatile solvents. Naphthalene is used as a fumigant/ pesticide mainly as well as in the production of dyes.(Ref.5)
We have looked at some of the benzenoid compounds; we use them in our everyday lives. Look at Nuggets to realize that some of these compounds are carcinogenic, some are explosives and some are also medicines. However, all are essential in our lives today.
Activities for Middle School Teachers:
Benzene has 3 different positions on the 6 carbon atoms: Immediately adjacent to the first carbon atom is called the ortho position, next to it is the meta position and directly opposite to it is the para position. Create the basic structure of benzene using kits available and then substitute different methyl groups in the different positions. Name them. Then change the hydrogen atom in the first position and insert an amine or hydroxyl group and repeat the process. Find out if such benzenoid compounds exist and what their names and uses are.
Also create structure of aspirin and salicylic acid. What is the latter used for?
Build structures for other pain relievers like ibuprofin and tylenol; find out their chemical/generic names as well.
Nuggets of Information:
Most of the benzene was originally obtained from coal tar, but from 1950, it has been derived from petroleum-based processes. More than half the benzene is converted to polystyrene, a common plastic. The steps to the conversion as as follows: benzene to ethyl benzene to styrene and then the polymer polystyrene.(Ref.1)
Benzene is one of the twenty most widely used chemicals in the United States. It is used mainly to manufacture plastics, lubricants, rubbers, dyes, detergents, drugs, and pesticides. You could breathe or ingest this aromatic compound easily in such environments.(Ref.2)
Benzene is present in cigarette smoke; in the presence of smokers we inhale benzene vapor. In fact, cigarette smoking causes half the exposure to benzene in the U.S.(Ref.2)
Benzene is a known carcinogen and workers who are constantly exposed to it are at a higher risk in developing leukemia and related cancers.(Ref.2)
Toluene derived its name from a tree in Colombia which has an aromatic extract called tolu balsam.(Ref.3)
TNT or tri-nitro-toluene is a known explosive and is made from nitric acid and toluene.(Ref.3)
Toluene is also used as an octane booster in gasoline. In biochemistry experiments toluene is used to rupture red blood cells for hemoglobin extraction.(Ref.3)
Phenols were the first surgical antiseptic used in 1865. Surgical amputations fell from 45% to 15% after using phenols. However, they were toxic as well.
A less toxic phenol like resorcinol, that contains two hydroxyl groups is often found in cough drops.(Ref.4)
Picric acid, which is trinitro phenol is used as a yellow dye as well as an explosive like TNT.(Ref.6)
Trace amounts of naphthalene are found in magnolias and certain kinds of deer.(Ref.5)
Naphthalene is considered to be a carcinogen; excessive inhalation or ingestion could cause hemolytic anemia.(Ref.7) Hemolytic anemia is caused by the destruction of red blood cells in the body.(Ref.8)
Aspirin, which is also known as methyl salicylate or 2 acetoxy-benzoic acid is an analgesic and is a non-steroidal anti-inflammatory agent. It is used usually for minor headaches and pains. Aspirin exhibits anti-coagulant properties(Ref.9) and therefore small doses are recommended every day to prevent heart attacks for some patients. It is an aromatic benzenoid compound.
Aniline, which is benzene with a hydrogen atom replaced by an amine _NH2 group is essential in the manufacture of dyes. It is responsible for the indigo color in blue jeans. Aniline is also used to make polymers like polyurethane, fungicides and herbicides. It is also used to make additives in rubber.(Ref.10)
References:
1.http://www.britannica.com/science/benzene
2.http://www.cancer.org/cancer/cancercauses/othercarcinogens/intheworkplace/benzene
3.http://ezinearticles.com/?Toluene—Knowing-Its-Chemical-Properties,-Applications-and-Risks&id=2214472
4.http://www.britannica.com/science/phenol
5.http://www.newworldencyclopedia.org/entry/Naphthalene
6.http://www.britannica.com/science/picric-acid
7.http://npic.orst.edu/ingred/naphth.html
8.http://www.nhlbi.nih.gov/health/health-topics/topics/ha/
9.https://pubchem.ncbi.nlm.nih.gov/compound/aspirin
10.http://study.com/academy/lesson/aniline-structure-formula-uses.html

Science Makes Sense-Week34: The other Alkali metals

April 25, 2016

Growing up, I was under the impression that potatoes were not good for you. Of course, my mother made them often and I enjoyed eating potatoes especially when fried. But I do remember the National Geographic feature on the merits of a potato and then I realized its significance as a great source of vitamins and minerals. A baked potato is high in potassium, an essential element needed in our bodies.
Potassium, like sodium, lithium, are part of Group 1A in the Periodic Table and are called alkali metals. They all have one lone electron in the ‘s’ orbital which makes them metals since they are willing to give it up to be a cation and have the outermost electronic structure of the closest neighbor, the inert noble gases. There are six alkali metals: lithium,Li, sodium,Na, potassium,K, rubidium,Rb, cesium,Cs and francium,Fr. Since the alkali metals are so reactive, it is never found in the elemental form in nature. Sir Humphrey Davy discovered Na and K in the early 19th century, while Li was discovered ten years later by a Swedish chemist. Later, Robert Bunsen, who invented the Bunsen burner, discovered Rb and Cs in 1860. Meanwhile, Fr was found in trace amounts and very little is known about its behavior.(Ref.1)
The alkali metals have a lot of properties similar to other traditional metals(copper, iron) like high conductivity, form cations easily, and are malleable and ductile. They have low ionization energy, i.e., the energy required to remove the outermost ‘s’ electron is not high. However, they are softer and silvery-white in color except for cesium which is yellow. In addition, their densities are lower than most metals and they have low boiling and melting points.(Ref.2)
They react very readily with oxygen when exposed to the air/oxygen to form oxides. Another important reaction is with water, when it vigorously reacts with it to form the hydroxides or alkalis, (which is responsible for its name) along with the release of hydrogen gas. This reaction is well documented in several videos to illustrate the increase in the rate of reaction as well as the increase in the intensity of the exothermic reaction as you go down this group of alkali metals. This particular video uses the same number of atoms of each alkali metal to react with the same amount of water each time and you will clearly see that the rate and intensity of the reaction increases significantly as you go down the group making cesium one of the most violent reactions to observe.(Ref.3)
The alkali metals react very easily with halogens to form the various halides.(Ref.1) No wonder sodium and potassium chlorides are found abundantly in nature.(Ref.4) In addition, the oxides of sodium and potassium react with carbon dioxide to form the various carbonates.(Ref.1) The alkali metals as hydroxides can easily react with nitric/nitrous and sulfuric acids to form the nitrates/nitrites and sulfates respectively.
Once we see the properties and reactions of alkali metals it is easy to see what are the salts of alkali metals available on the earth’s crust. Besides the fact that sodium chloride is found abundantly on the earth, we also find sodium carbonate, sodium nitrate(saltpetre), and sodium sulfate. Sodium nitrite is used extensively in the manufacture of gunpowder. The pulp and paper industry uses the hydroxide, carbonate and sulfates of sodium. Sodium sulfate is also used in the manufacture of cardboard and brown paper. Sodium carbonate is used in power companies to absorb sulfur dioxide which is a serious pollutant. NaOH, sodium hydroxide is one of the top ten industrial chemicals, while sodium bicarbonate, baking soda, NaHCO3, is invaluable in the food industry.(Ref.4)
Meanwhile most of the potassium is used as a fertilizer. KOH, potassium hydroxide is used for detergents,KClO3 potassium chlorate is needed in the manufacture of explosives while KBr, potassium bromide is essential in the photography industry.
(Ref.4)
The next three alkali metals, rubidium, cesium and francium are much less common. Rubidium is sometimes used for the treatment of depression, while cesium is mainly used in the manufacture of certain kinds of glass and radiation detection equipment. It is also used to make the atomic clock which will be explained more under Nuggets. But the main use of francium is in research, along with rubidium as well.(Ref.4)
The role of two of the alkali metals, sodium and potassium in our bodies cannot be underestimated. Both these alkali metals function as cations in our body; in other words they are charged particles that carry an electric current across our cells causing many physiological processes. It is important to maintain a balance of the sodium and potassium ions; ideally we need 3 times as much potassium as sodium in our bodies. Sadly we tend to consume more sodium containing products versus potassium containing products.(Ref.5) (More under Nuggets)
Even though the higher group alkali metals like rubidium, cesium and francium have limited uses, our lives would be cut short without the salts and hydroxides of the other alkali metals.
Activities for Middle School Teachers:
Look at the various halides formed by the alkali metals. Does it follow the multiplication principle? How about oxides and hydroxides? Do they follow that same principle? Why or why not?
How do we lose sodium from our bodies? What are the main sources of sodium in our diet? What are the common diseases associated with high sodium in our diets? Study the increase or decrease in these illnesses based on diet in various different countries over a 50-year period.
Nuggets of Information:
Sir Humphrey Davy who discovered two of the alkali metals, was born in Penzance, Cornwall, England. He was known as a wild man in the laboratory, often smelling and tasting the products of his experiments, which almost certainly shortened his life.(Ref.1)
The colors of the alkali metal salts are distinctive and are often used in the flame test to determine the cations of lithium, sodium and potassium. Chlorides of these cations are mixed with a little hydrochloric acid and placed on the blue upper part of a Bunsen flame. Lithium shows a crimson color, sodium the characteristic golden-yellow color and potassium has a lilac color.(Ref.6) Rubidium gives a dark red color, while cesium has a blue color.(Ref.4)
Potassium exists as sylvite, KCl on the earth’s crust.(Ref.4)
Both cations of potassium and sodium are found inside and outside a cell membrane in our bodies. The difference in the concentrations of these ions on each side of the cell membrane is called a membrane potential. The membrane potential uses the charge differences to conduct electricity between cells. This electricity then helps perform the work of contracting muscle, transmitting nerve impulses and maintaining the heartbeat. Processed foods increases the amount of sodium in our bodies, while foods like baked potatoes, prunes, spinach, bananas are good sources of potassium.(Ref.5)
Cesium has been used in the manufacture of atomic clocks that keep the best time. How does it work? Prior to 1964, the International Standard second was based on the orbital period of the earth. However, the cesium clock period was found to be much more stable. Using the 133 atomic mass of cesium, we focus on the lone electron outside the 54 electron core. This electron interacts with the nuclear spin and has an energy splitting called hyperfine structure. This splitting allows us to measure time with a precision of one second in 1.4 million years!(Ref.7)
References:
1.http://chemwiki.ucdavis.edu/?title=Textbook_Maps/General_Chemistry_Textbook_Maps/Map:_Chemistry_(Averill_%26_
Eldredge)/21:_Periodic_Trends_%26_the_s-Block_Elements/21.3:_The_Alkali_Metals_(Group_1)
2.http://www.buzzle.com/articles/alkali-metals-properties-of-alkali-metals.html
3.http://www.bing.com/videos/search?q=reaction+of+alkali+metals+with+water&view=detail&mid=32
DA092AA85B40F0218232DA092AA85B40F02182&FORM=VIRE
4.http://www.scienceclarified.com/A-Al/Alkali-Metals.html
5.http://healthyeating.sfgate.com/right-balance-sodium-potassium-6341.html
6.https://www.youtube.com/watch?v=k-ZsaTXiz9w
7.http://hyperphysics.phy-astr.gsu.edu/hbase/acloc.html

Science Makes Sense-Week33: Lithium, the little pill that can

April 18, 2016

I shall never forget that call from my dear friend who needed me when her husband had a manic episode in the 80’s. Those were the days when I had barely heard of mental illnesses and least of all anything about manic depression/bipolar disorders. On a wintry morning, I drove over to her place to give her some company and comfort. He had been taken in restraints to the hospital. After years of being treated with ‘lithium’ he is the charming intelligent human being I knew before that incident. Now he is able to take care of his family and himself. This ‘lithium’ is chemically lithium carbonate which has been used successfully by several psychiatrists to treat mental illnesses like bipolar disorders.
Lithium,Li, is the first in the alkali metals and is one of the smallest atomic solids on the second period of the Periodic Table. As a metal it is highly reactive, and when added to water, reacts explosively to form the alkali lithium hydroxide.(Ref.1) In nature, lithium is found as a mixture of the two isotopes Li6 and Li7. Soft and silvery-white, Li has a low melting point but has a high specific heat. It seems to behave more like the alkaline-earth metals than the alkali-metals. (Ref.2)
Being very reactive, it does not usually exist as metallic Li but as the hydroxide, LiOH. It is one of the few elements to react easily with nitrogen to form a black nitrite. It reacts with hydrogen at higher temperatures around 500 degrees C to form lithium hydride, LiH. (Ref.2)
Uses: Main industrial uses of Li is as a lubricant grease thickener, in the glazing of pottery and to extend the life and storage of alkaline batteries. Lithium carbonate, Li(CO3)2, is used mainly to treat bipolar disorders. What is bipolar disorder or BD as it is often called? It is a mental condition that causes extreme shifts in a person’s energy levels. The person affected by this disease could be extremely agitated and ‘manic’ with racing thoughts for days/months and then come crashing down feeling major depression and guilt for their earlier actions. These mood shifts are very different from those that everyone else goes through, because people with BD could be totally impaired in their abilities to complete day-to-day tasks when suffering from this disorder.(Ref.3) When Li was discovered in 1817, it was used initially in the treatment of gout and physicians could tell that it was good as a mood stabilizer. The Australian psychiatrist, Dr. John Cade published the first paper on the use of lithium in the treatment of acute mania in 1949, but it was not until 1970 that the U.S.FDA approved it. (Ref.4)
The chlorides and bromides of Li are also used in absorbing humidity and hence in air-conditioning systems. Alloys of Li with cadmium, Cd, manganese, Mg, copper, Cu, are used in the manufacture of high-performance aircraft parts.(Ref.2)
Lithium’s role in the treatment of bipolar disorder or BD has undergone several modifications, but the key role is how it helps in reversing structural abnormalities in the brain/biochemical changes in the brain because of BD.
First Li ions help in decreasing second messenger systems in the brain, protects the nerves in the brain. BD patients have grey matter reductions especially in the medial frontal cortex and the hippocampus regions of the brain; Li ions once again help in reversing these effects. Overall, Li treatment(in the form of lithium carbonate/lithium ions) helps in maintaining the nerve plasticity of the brain. (Ref.5). It is almost as if this tiny metal ion is able to go around the brain and repair problems that cause BD in patients!
Activities for Middle School Teachers:
Students can study the ionic radii of elements in the first three periods and try to understand what the relative sizes of the cations and anions are. Is there a correlation with the increase/ decrease of radii based on the group or period ? Why?Create a graph for each of those periods using ionic radius of the element versus its atomic number. Is it a straight-line variation? How does the size of the lithium ion compare to other elemental ions?
If a model of the brain is available, the teacher needs to spend time talking about the different parts of the brain, including the hippo-campus and the frontal and medial cortices. What are the functions of the various parts of the brain?
Let the teacher spend time talking about several kinds of illnesses versus mental illnesses. Discuss how families are more open to talking about physical illnesses in loved ones versus mental illnesses. How are psychiatrists viewed in societies as opposed to other kinds of medical doctors? Is there a difference? Why?
Nuggets of Information:
Lithium is moderately abundant on the earth’s crust: 65ppm.(Ref.2)
In the U.S.,lithium is recovered from brine pools in Nevada while most commercial lithium is obtained from Chile.(Ref.2)
Compounds of Li and acetylene are used in the manufacture of Vitamin A.(Ref.2)
Bipolar disorder was officially known as manic depression in the 80’s.
The National Institute of Mental Health(NIMH)estimates 2.6% of U.S. adults suffer from BD, which is approximately 600,000 people in the U.S. More than 80% of these cases are classified as severe.(Ref.3)
Research has never indicated that bi-polar illness is because of lithium deficiency; rather that lithium carbonate acts as a mood stabilizer.(Ref.5)

References:
1.http://chemguide.co.uk/inorganic/group1/reacth2o.html
2.http://www.lenntech.com/periodic/elements/li.htm
3.http://www.everydayhealth.com/bipolar-disorder/guide/
4.http://bipolar.about.com/od/lithium/a/010312_lithium1.htm
5.https://www.dnalc.org/view/2085-Lithium-how-it-might-protect-the-brain.html

Science Makes Sense-Week 32: Chemistry and Social Justice-Pesticides

April 11, 2016

Rachel Carson, wrote her book “Silent Spring” in 1962 and changed the way we looked at pesticides especially DDT. She may have been quite responsible to have initiated the environmental movement of today. But along with this movement, we continue to produce a lot of new pesticides that make your head spin when you do a search on the internet! So in the 21st century, when we talk of pesticides, it covers such an extensive area that we are not only looking at chlorinated organo-compounds like DDT but so many others including, to name a few, herbicides, fungicides, rodenticides as well.
Today we shall look at the chemical composition of many common pesticides, fungicides etc., their classifications and understand how it impacts humans and the environment. We will also touch on what are the alternatives to using synthetic pesticides.
The word “pesticide” is used to describe a substance (or mixture) that kills a pest, or it can prevent or minimize the damage that a pest causes. Examples of pests include insects, mice or other animals, unwanted plants (weeds), fungi, bacteria or viruses. Pesticides can also include any substance that is used to modify a plant. They are usually chemicals, but can also be made from natural materials such as animals, plants, bacteria, etc.(Ref.1)
The chemical families that most pesticides belong to are the following, organo-phosphates (organic compounds containing phosphorus), chlorinated hydrocarbons including DDT, carbamates (salts from carbamic acid which is really formic acid,HCOOH, with its free hydrogen replaced by an amine NH2 group). There are also thiocarbamates (‘thio’ is when an oxygen atom, O, is replaced by a sulfur,S, atom) and pyrethroids. Pyrethroids are benzenoid derivatives of pyrethrum which is obtained from chrysanthemums. Pyrethrum has the characteristic cyclopropane structure along with hydrocarbon chains with oxygen.(Ref.2)
How do all these different kinds of products broadly called insecticides affect humans and the environment?
Let us first look at its effects on humans. Starting with mild results like headaches and nausea, pesticides can also cause more serious and lasting health effects such as cancer, disruption of the endocrine system and reproductive harm. Disruption of the endocrine system means that the complex production of hormones is disturbed, resulting in infertility and babies born with birth defects. Children are especially susceptible to pesticides, because till the age of twelve, their brains are not fully developed and pesticides can impact the central nervous system.(Ref.4)
Pesticides affect the environment as well. Depending on whether the pesticide is water soluble or fat soluble, it can enter water bodies or get into fish and other aquatic life. Then when we as humans ingest them, we get health problems as well.(Ref.4)
In short, these are the harmful effects of all kinds of pesticides:
1. Pesticides damage ecosystems
2. They may damage/harm un-targeted animals(see Nuggets under ‘bioamplfication’)
3. Pesticides decrease biodiversity
4. Pesticides may cause a decline in populations and/or extinction of species
5. Pesticides “mess up” food chains/webs
6. Pesticides disrupt the ecosystems’ natural balance.
(Ref.4)
Knowing all this, organic farmers try going in one of two directions. The word ‘organic’ here has nothing to do with the definition in chemistry, it simply means the use of no pesticides or the absence of synthetic fertilizers. When they use no pesticides they allow crops to be spotted or eaten by a few pests and not look ‘perfect’ and allow weeds to coexist with crops/or do a lot of hand weeding. The alternative is to use naturally grown pesticides like pyrethrum that comes from chrysanthemums instead of synthetically applied pesticides and pheromone traps. Too much application of these pesticides can also lead to toxicity, so organic farming is a tricky business. But crop rotation, sprays and pheromone traps combined with minimal use of even naturally obtained pesticides by organic farmers will lead to less toxicity in humans and the environment.(Refs.5,6)
Activities for Middle School Teachers
Study the time-line of the different kinds of pesticides from the early 60’s to right now out there. How ‘natural’ are some of these pesticides? Take students on a field trip to organic farms and orchards. What alternative types of pest control is used here and how effective are they?
Look at the chemical structures of the different pesticides and note if there is a connection between type of chemical classification and specific use of the pesticide.
Nuggets of Information
Pesticides kill or repel insects and include bug sprays/repellants, baits, commercial and garden sprays, shampoos and moth balls. Herbicides kill weeds and unwanted plants. To achieve this we use weed killers, weed and feed fertilizers and tree stump treatments. Meanwhile, fungicides kills mould, mildew and other fungi. here we use commercial/ garden flower sprays,treated seeds and paint additives. Rodenticides kill all kinds of rodents using mouse and rat baits. Then we have disinfectants to kill bacteria, mould and mildew and use bleaches, ammonia, kitchen and bathroom cleaners as well as pool and spa cleaners. Finally, wood preservatives protect wood from insects and fungi and we use pressure-treated wood.
(Ref.1)
Broad Spectrum: Insecticides vary in what insects they kill. Some kill only a few types of insects. Then you could choose these insecticides when you wish to kill only one insect pest and not other beneficial insects in the area. Many insecticides are wide range killers or “broad spectrum”. Such pesticides are used when several different kinds of insects are a problem. One chemical can kill them all. No broad spectrum insecticide kills all insects; each varies as to the kinds of insects it can control.
Narrow Spectrum: While many insecticides are broad spectrum, a new group of insecticides attack the central nervous system, and are much more selective. The chitin inhibitors only affect animals with chitin in their exoskeleton (i.e. insects). (Chitin is the growth on an insect and inhibiting that growth can also kill the insect.) Growth regulators are even more specific. They affect certain groups of species that have a particular hormone. Finally, when we talk about pheromones, they are the most restrictive because they react with only one species or one sex of a single species.(Ref.3)
When grasshoppers, that are lower on the food chain eat pesticide-laden foods, they get the toxins in their systems. Then shrews, who are their predators, eat several grasshoppers and get more of the toxins in them. Owls in turn, eat several shrews and get even more toxins in them. This process is called Bioamplification. Remember, there could be a decrease in the owl population which may die because of so many toxins in their systems, leading to an increase in shrew population and a consequent decrease in grasshoppers. All this leads to a complete change in the balance of species.
Cesar Chavez was a fighter for better working conditions for the California grape and lettuce pickers. He gave the famous ‘wrath of grapes’ speech in the 80s after twenty years of organizing and forming a union called the United Farm Workers(UFW) in California. He urged the government to ban the use of pesticides in the growing of grapes, demanded better working conditions, better pay for the workers not only in California, but all over the country..(Ref.7)
References:
1.http://www.ccohs.ca/oshanswers/chemicals/pesticides/general.html
2.http://chemistry.about.com/od/factsstructures/ig/Chemical-Structures—P/Pyrethrin-I.htm
3.http://psep.cce.cornell.edu/Tutorials/core-tutorial/module13/index.aspx
4.http://www.toxicsaction.org/problems-and-solutions/pesticides
5.http://www.livinghistoryfarm.org/farminginthe70s/pests_10.html
6.https://www.ocf.berkeley.edu/~lhom/organictext.html
7.http://www.imahero.com/is/bios/cesarchavez.html


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