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Science Makes Sense, Week 18: Periodic Table, order

December 28, 2015

Organize, categorize, use colored stickers to mark differences. This is how we arrange and try to understand differing groups in any subject we study. Chemistry is no different. As soon as the definition of elements was laid out, chemists set about discovering new elements and placing them together initially based on melting points, density, and boiling point data. Today with knowledge about atomic mass, atomic number and the internal structure of an atom we have a clear, concise way of classification called the Periodic Table.

The History of the Periodic Table is a fascinating study by itself in the field of chemistry. Although elements like gold, silver, copper, tin, mercury, lead (Au, Ag, Cu, Sn, Hg,Pb) were known since the alchemists, the first official discovery of an element, phosphorus, P, took place in 1649 ( Week 17). The next 200 years, 63 elements were discovered and could be classified. (Ref. 1)

Law of triads: Initially, bunches of 3 elements were found to have similar properties. For example, the atomic weight of strontium, was found to be between calcium and barium and similarly flourine, chlorine and bromine were found to be similar in properties. So there was a theory floating about bunches of 3 elements with similar properties. With the discovery of more elements in these bunches, one could see that the law of triads was a limited idea. (Ref. 1)

Using a special kind of cylinder, it was seen that every 16 elements showed similar properties. This was one of the first attempts in the classification of elements. (Ref. 1)

Chancourtoisin in 1862 was the first to recognize that elemental properties recur every seven elements, but it was Dimitri Mendeleev, the Russian chemist who is credited with the first credible periodic table of 63 elements. What was so remarkable was the fact that he was able to predict properties of elements that were in the gaps long before they were discovered, based on their possible position in the table. (Ref. 1)

The discovery of sub-atomic particles, the discovery of atomic numbers for elements in the 20th century, paved the way to organize the Periodic Table as it is today. (Ref. 1) The presence of a certain amount of order in the electronic arrangement in different shells led to the arrangement of elements in groups of two, eight and eighteen. The pattern of arrangement of these elements give us invaluable information; no wonder the Periodic Table is considered the backbone of Chemistry!

Activities for Middle School Teachers:

Take a bunch of household items and categorize them like a periodic table. Justify your classifications!

During harvest season, let students bring pumpkins and carve the name of an element in each pumpkin to create a Periodic Table of pumpkins. Use other items, like leaves, pieces of different colored cloth, to do the same thing.

Do a research project on the different kinds of Periodic Tables created.

Nuggets of Information:

Each row of the Periodic Table is called a period and each column is called a Group. For example, there are only two elements, Hydrogen,H and Helium, He, in the first period of the Periodic Table. Elements in a group exhibit similar behavior: alkali metals, Lithium,Li, sodium, Na, potassium K, through Francium, Fr, (elements in blue) have similar properties. Again, the Noble Gases in Group 8 ( Helium, He, Neon, Ne, Argon,Ar. etc) are inert and do not react with anything. Elements in a Group have an identical outer shell electronic arrangement. (Ref.3)

Ninety elements in the Periodic Table occur in nature; the rest have been synthesized in the laboratory. (Ref.3)

Technitium was the first element to be made in the laboratory. (Ref.3)

The present Periodic Table has room for 118 elements. (Ref.3)

References:

1.https://www.wou.edu/las/physci/ch412/perhist.htm

2.http://fivejs.com/wp-content/uploads/2011/08/Periodic-Table-of-the-Elements-12pg.pdf

3.http://chemistry.about.com/od/periodictables/a/10-Periodic-Table-Facts.htm

Click to access Periodic-Table-of-the-Elements-12pg.pdf

Tags:arrangements, honduras border, Periodic table
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Science makes Sense, Week 17: Phosphorus, fertilizers, ATP , LEDs , phossy jaw and wars.

December 12, 2015

When we were growing up in India, power failures were common and we all had candles and matchboxes handy. The sides of those little boxes had a brownish- red tint and we struck our little match – heads on the sides to light them and light up candles. Later, we saved the match- boxes to play games. We made miniature furniture, or used them to save our trinkets and little stickers.

The match- heads had phosphorus. The chemical symbol is P and it is the 15th element in the Periodic Table. It is part of the Nitrogen Group, in between Silicon and Sulfur. Next to Calcium, Ca, Phosphorus is the most abundant element in the body. (Ref.1) It is essential in the building blocks of our bones and genes,viz.,the DNA and RNA. Actually most of us have more P than we need since it is found in a lot of foods that we eat.

Phosphorus was discovered in 1669 while working with urine! Hennig Brand, a German alchemist, heated the residue left behind after the evaporation of urine. Elemental phosphorus was discovered. In nature, one never finds elemental P but it is always found as rock phosphates. (Ref. 2) A hundred years later, it was extracted using bone , which has become the traditional way of chemically producing phosphorus. (Ref. 3)

Phosphorus, P, exists in 3 allotropic forms, red, white and black. Red and white are more common. (Nuggets of Information) Both red and white P are poly-atomic and are 4 P atoms that form a tetrahedron. (Fig.3) White phosphorus reacts vigorously with oxygen and the reaction results in a popping sound that is similar to a dog barking. Phosphorus pentoxide is formed during the oxidation process (Ref.4):

P₄+ 5O_{2 →} 2P₂O₅

The chemical behavior of phosphorus is interesting because as a non-metal it exhibits ionic and covalent bonding depending on where it is present. It is an important element in complex organic compounds like ATP, (adenosine tri-phophate) as well as in simpler molecules like phosphoric acid ,H₃PO₄, oxides of phosphorus, or as a phosphate, PO₄^3- in an inorganic compound. ATP is an energy-bearing molecule present in all living organisms. (Ref.5)(Fig.3)(Nuggets of Information)

The most common use of phosphorus is in the manufacture of fertilizers. It is also used in the production of steel and was used extensively in the manufacture of detergents, though lately phosphate-free detergents are more prevalent. This is because the phosphates that leached into water bodies affected it adversely.

There is much talk about peak phosphorus today. This means that our demand is exceeding the supply of phosphorus. In 2008, the world was shocked by an 800% increase in the price of phosphorus. Several factors including world reserves, agricultural practices using excessive amounts of manufactured phosphates have played a role in this shortage. As a society, we need to be cognizant of these problems and figure out ways to counteract the decrease in phosphorus. (Nuggets of Information)(Ref. 6)

Activities for Middle School Teachers:

Phosphorus has several allotropes. What other elements exhibit allotropism?

Study several biological processes that need ATP. (Nuggets of Information)

Study the reaction of phosphorus with the halogens( F, CL, I, Br, At) and balance the equations.

Nuggets of Information:

Phosphorus is named from the Greek phrase:’bringer of light’. (Ref.7)

Phosphorus exists as mainly three allotropes: red, white and black. The red and white form have a tetrahedral structure with 4 phosphorus atoms at each corner of the tetrahedron. (Fig.3) The black allotrope has a layer-like structure where one layer of P atoms are layered over another. The red allotrope has a hard crystalline structure and is non -poisonous and more stable than the white or yellow allotrope. The white P is soft and waxy, poisonous and spontaneously combusts in the presence of oxygen. Black P is the least reactive form and has a metallic lustre. (Ref.8)

Phosphoric acid is added to cola drinks to give it their sharp taste. (Fig. 7) Magnesium phosphide, Mg₃P₂, is used as warning flares and phosphorus, P, is used in Light Emitting Diodes or LEDs. (Fig. 7)

Knowing the combustible nature of white P, one of the most awful uses of White P has been in warfare. From World War 2, it has been used in tracer bullets, firebombs and in Middle East wars, where victims are burnt in horrific ways. Lately P has been used to make nerve gases like Sarin and was released in a Tokyo subway in 1995. White P was also used to make matches in the 19th century, but no-one realized how deadly the vapours were till the young girls working in the factories developed phossy jaw, which ate the jaw bone. (Fig. 7)

As mentioned earlier, too much P in water can make it a pollutant, choking the biological life in streams and lakes. What happens is that there is too much plankton growing that kills fish and other water life. There is also prevention of sunlight from reaching lower levels of the water, thereby killing several species there as well. This process is called eutrophication. (Ref. 9)

Just like there is a nitrogen cycle in nature, we have a phosphorus cycle as well. It differs from other cycles because the gaseous phase is minimal. Most of the phosphates are found in sedimentary rocks. When it rains, the process of erosion and weathering distributes the P in the soil and water. Plants absorb the phosphates and animals eat the plants. The phosphates are returned to the earth and rocks through the urine and feces from animals, as well as during decomposition and death of animal and plant matter. Aquatic eco systems also imbibe the phosphates through sewage seepage, fertilizer runoff and from industrial wastes. Animals eat the plants and the process is continued as before.

Phosphorus is found in a lot of foods we eat. Many lentils, meats and fish like salmon contain P. In addition, a lot of nuts like Brazils, cashews and almonds contain P.(Ref.10)

Adenosine-Tri-Phosphate, or ATP is the energy currency in several cell mechanisms. During respiration and exercising, which means almost all the time, ATP is necessary for all living beings. The structure of ATP has an ordered carbon compound as the main part; however the phosphorus is critical. Three of the phosphorus atoms are linked via oxygen atoms and there are extra oxygen atoms attached to each of them as well. The negative charges on the oxygen when the hydrogen leaves as a proton on the hydroxyl groups, OH, makes them have high potential energy. This means they are not stable and are willing to lose a phosphate ion from an end to form ADP, Adenosine-Di-Phosphate. The conversion of ATP to ADP releases about 7.3 Kcal per mole. Living things use ATP like a battery, since it powers reactions by losing a phosphate and becomes ADP. Food energy converts the ADP once again to ATP and the process is repeated. (Fig.3)(Ref. 11)

References:

Tags:ATP, LEDS, phossy jaw, wars
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Science Makes sense, Week 16: Chemistry and Social Justice, hair and nail salons,glues,EMA and Brazilian Blowout

December 6, 2015

The rituals with hair are seen all over the world. In India, hair and its maintenance is probably still a time-consuming job for mothers with young girls and boys. I am still struck by little children going to school in India with shiny black hair neatly combed for boys and braided evenly for the girls as they trot to school. It does not matter how poor the family is, the children are very well-groomed.

My mother would spend everyday combing, oiling and braiding my long hair before we rushed off to school. Then, during the weekend, ‘oil bath’ and local powders called ‘Sheekapodi’ were used to clean the hair. The concept of shampoo was non-existent let alone entering hair salons. Today nail and hair salons proliferate not only in western countries, but in India as well.

We will look at the chemicals used in hair and nail salons and talk about the effects they have especially on the workers.

Toluene is used in nail gluing, nail polish and in hair straighteners. This organic compound is benzene with a methyl group attached. (Benzene is basically a cyclic compound with 6 carbons and 6 hydrogen atoms.) Short -term exposure may cause dizziness, rashes and ear-nose -throat (ENT) irritation. Acetone is a nail polish remover and is also available in any supermarket. This also causes dizziness, skin problems and long-term exposure leads to birth defects, if the workers are pregnant. Formaldehyde is used for nail polish as well as a nail-hardener: causes breathing problems, coughing , skin rashes and is an ENT irritant. Long-term exposure could lead to cancer. Another organic compound shown as #4 in the second figure, di-butyl phthalate, is used like formaldehyde and causes nausea, dizziness along with birth defects with long-term exposure. And then there is EMA, which is ethyl methacrylate (#5, Fig.2), used in artificial fingernails, that causes similar problems in workers. (Ref. 1,2)

Needless to say, I have looked at only a few chemicals in the nail salon industry. In addition, when it comes to hair salons, there are many products to worry about. A ‘perm’ or permanent was done at home by women who grew up in the ’50s. Women used keratin , a protein that actually weakens hair. (Ref. 3 and in Nuggets of Information) Weaving of hair is done not just in the African-American community, but now every celebrity/person with money who wants fuller, thicker hair can get it done. There are men , besides women, who are going in for hair extensions. The process involves stitching, gluing human hair to the scalp and can cause severe skin rashes, allergies and even loss of hair. These glues also affect the workers who inhale it all the time. (Refs.1,4,5) The glue contains styrene, an ethene attached to a benzene molecule. It causes dizziness, headaches and long- term exposure may lead to cancer. (Ref.1 )(Fig.3) Then there is the above-mentioned formaldehyde that is used in creating Brazilian Blowout, a hair treatment that will straighten curls and frizz or create it. We already know that it is toxic for the workers. Ref.6)

The list of toxic chemicals goes on and on. There is more information under Nuggets of Information. I have included some alternatives to the regular list of hair and nail salons. But we must look not just for our own health concerns but those of the workers who are constantly exposed to this barrage of toxicity. The good news is that awareness is growing, there is more advocacy for the workers, but all that is being done is just a drop in the bucket. More needs to be done to change this love affair we have with the dead cells in our bodies.

Activities for Middle School Teachers:

Talk about hair and nail grooming practices in different parts of the world. Students will learn geography and culture all over the world.

Study the history of African-American hair and special hair salons for them.

Go to the supermarket and check out the hair and nail products division and study the chemical ingredients in all of them. Let students do a presentation on the chemical structure, usage of product and its toxic side-effects.

Study hair styles through the ages especially in the United States focusing on Caucasian and African American groups.

Nuggets of Information:

Human hair export, from India, is a multi-million dollar industry. Indians, especially Hindus, believe in shaving off all their hair as a gift to the gods. Men and women with long black hair, frequently go to temples to be shorn of their tresses. The demand for wigs and hair extensions is high in the US, UK and parts of Europe. (Ref. 7)

Nails and hair are considered extensions of the skin. Hair and nails cells grow at the base of the root, and when they move upward, they are cut off from nourishment to form a hard protein called keratin. This keratin and the dead cells form the shaft of hair or nail. (Ref.8)

Four out of ten workers in the nail and salon industry are poor Asians with limited English-speaking skills, uninsured and working in badly-ventilated spaces. Fortunately, ACLU and other labor organizations are advocating for their awareness of a safe environment to work in. The California Health Nail Salon Collaborative, along with environmental and community organizations are trying to ban the ‘toxic trio’ of formaldehyde, dibutyl-phthalate and toluene in hair/nail salons. (Ref.7)

Celebrities like Jennifer Anniston have come out openly to talk about the hazards and adverse effects of hair extensions. Some famous singers have had bald patches in their hair because of these extensions. Perhaps the public will not be swayed and charmed by the commercials that laud their beauty. (Ref.9)

Recently, there is an increase in American NFL football players with long dreadlocks. Some of them could be wearing hair extensions, since they are getting popular among men now. (Ref. 10)

How does a ‘perm’ work? The protein molecules in the hair called keratin are arranged in straight molecules joined by disulfide bonds (-S-S-) which gives strength to the hair. (Actually the amino acid cystein in the keratin molecule forms the -S-S- bond with another cystein in a second keratin molecule.) Ammonium thioglycolate, (HSCH₂CO₂NH₄) or ‘thiol’ can break the bonds and allow manipulation of hair: either put in curlers to curl straight hair or use a flat iron to straighten curly hair. This is a reduction process (which is opposite of oxidation) and oxygen is lost or hydrogen is added. Following this Hydrogen peroxide, H₂O_{2 ,}is added to strengthen the hair, an oxidation process.

Sometimes, lye soap is used instead of ‘thiol’. Lye is a 10% solution of NaOH or sodium hydroxide which does the same reduction; then it is thoroughly washed out with conditioner and water to prevent corrosion of the scalp. (Ref.11) As you can see, continuous perming of hair can lead to seriously damaged hair.

Some encouraging news to help us modify our nail and hair salon addictions:

Jenna Hipp has come up with nail polishes that avoid the toxic- trio chemicals, check out her other products. (Ref.12)
Campaign for Safe Cosmetics is an advocacy group that helps workers and consumers make smart choices and are aware of the hazards and side effects of products that keep coming out in the cosmetics industry. (Ref.13)
No more dirty looks is a blog site with good alternatives for hair products. Check out their book as well. (Ref. 14)

References:

1.http://www.womensvoices.org/avoid-toxic-chemicals/salon-products/toxic-chemicals-in-salon-products-workers/

2.http://www.scientificamerican.com/article/these-4-chemicals-may-pose-the-most-risk-for-nail-salon-workers/

3.http://www.ask.com/beauty-fashion/chemicals-used-perming-hair-79b66ed09938762a

4.http://www.consumerreports.org/cro/2013/02/the-dangers-of-hair-extensions/index.htm

5.http://www.nydailynews.com/life-style/hair-extensions-latest-well-tressed-man-article-1.1497062

6.http://www.alternet.org/story/155982/toxic_chemicals_in_hair_and_na il_salons_create_serious_suffering_in_the_name_of_beauty/

7.http://www.scienceandnature.org/IJEMS-Vol2(4)-Oct2011/IJEMS_V2(4)4.pdf

8.http://kidshealth.org/teen/your_body/body_basics/skin_hair_nails.ht ml

9.http://www.dailymail.co.uk/femail/article-2274414/Dangers-hair-extensions-Blinding-headaches-bleeding-scalps-permanent-baldness.html

10.http://www.nydailynews.com/life-style/hair-extensions-latest-well-tressed-man-article-1.1497062

11.http://www.humantouchofchemistry.com/the-chemistry-of-perming-rebonding.htm