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Thursday, 8 June 2017

KIMIA ORGANIK

Daripada Wikipedia, ensiklopedia bebas.
Kimia organik ialah kajian sains mengenai struktur, ciri-ciri, komposisi, tindak balas, dan sintesis sebatian organik. Pengajian kimia organik kini lebih mementingkan mekanisme tindak balas berbanding dengan siri homolog sebatian organik itu.

Tatanama Organik[sunting | sunting sumber]

Tatanama organik ialah sistem yang diadakan bagi menamakan dan mengelaskan sebatian organik. Tatanama organik yang perlu digunakan ialah sebagaimana yang disarankan oleh Kesatuan Antarabangsa bagi Kimia Tulen dan Gunaan (International Union of Pure and Applied Chemistry, IUPAC). Peraturan-peraturan tatanama yang ditetapkan mengikut Saranan 1979 dan 1993 boleh didapati di laman web ini.

Sebatian organik[sunting | sunting sumber]

Sebatian organik ialah sebatian yang mengandungi unsur karbon kecuali oksida karbon (karbon monoksida dan karbon dioksida), sebatian karbida, sebatian sianida, sebatian karbonat, dan sebatian bikarbonat. Sebatian-sebatian organik yang mudah boleh dikelaskan mengikut kumpulan berfungsi yang hadir dalam sebatian itu. Kehadiran kumpulan berfungsi tersebut seterusnya akan menentukan siri homolog sebatian tersebut.
Antara siri homolog yang penting ialah:

Sebatian Alifatik[sunting | sunting sumber]

Sebatian alifatik ialah sebatian organik yang mana molekulnya tidak mengandungi sistem haruman.

Sebatian Haruman[sunting | sunting sumber]

Sebatian haruman ialah molekul organik yang mengandungi satu atau lebih sistem haruman cincin. Contoh-contoh sebatian haruman ialah benzena, fenol, dan toluena.

Sebatian Heterosiklik[sunting | sunting sumber]

Sebatian Heterosiklik ialah molekul organik bergelung yang setiap gelung mengandungi sekurang-kurangnya satu heteroatom. Contoh-contoh sebatian heterosiklik ialah pyridina, furan, dan thiofena.

Polimer[sunting | sunting sumber]

Polimer ialah molekul yang khas. Biasanya dianggap molekul "besar", polimer mendapat reputasi bersaiz sedemikian kerana terdapat molekul yang mengandungi segmen yang lebih kecil. Segmen ini boleh dikenal pasti secara kimia yang menjadikan molekul sedemikian sebagai homopolimer atau struktur kimia segmen yang pelbagai, yang menjadikan molekul itu heteropolimer. Polimer ialah subset "makromolekul" yang hanyalah pengkelasan untuk semua molekul yang dianggap besar.
Polimer boleh jadi organik atau tak organik. Polimer yang biasa dijumpai biasanya organik (contoh. polyethylene, polypropylene, Plexiglas, dll.). Tetapi polimer tak organik juga biasa dalam kehidupan seharian (contoh. silly putty, silikon, dll.).

Konsep[sunting | sunting sumber]

Ciri-ciri unsur organik[sunting | sunting sumber]

Sebab terdapatnya begitu banyak sebatian karbon adalah kerana unsur karbon mempunyai keupayaan untuk membentuk rantaian karbon yang mempunyai pelbagai panjang dan saiz gelung (penguntaian). Kebanyakan sebatian karbon amat sensitif kepada haba, dan biasanya terurai bawah 300°C. Sebatian karbon biasanya kurang larut dalam air berbanding garam tak organik lain. Berlainan dengan garam sedemikian, sebatian karbon biasanya lebih mudah larut dalam pelarut organik seperti eter atau alkohol. Sebatian organik terbentuk daripada ikatan kovalen.

Menentukan struktur molekul sebatian organik[sunting | sunting sumber]

Pada masa kini, terdapat beberapa cara untuk menentukan struktur sebatian organik. Secara umumnya:
  • Kristalografi: Kaedah paling tepat tetapi mahal. Hanya boleh digunakan apabila sebatian tersebut dapat membentuk kristal.
  • Analisis Unsur: Kaedah menghancurkan untuk menentukan komposisi unsur molekul.
  • Spektroskopi infra merah: Biasanya digunakan bagi menentukan kehadiran (atau ketiadaan) kumpulan fungsi tertentu.
  • Spektrometri jisim: Digunakan untuk menentukan berat molekul sesuatu sebatian dan pola serpihan.
  • Spektroskopi resonans magnetik nuklear (RMN): Dapat menentukan kehadiran nukleus yang bersifat magnetik dan membuat deduksi tentang persekitarannya berdasarkan kepada anjakan kimia.
Lihat kimia analisis untuk kaedah lain.

Sejarah[sunting | sunting sumber]

Pada awal kurun ke-18, kimia organik dianggap sebagai satu cabang kimia yang mengkaji bahan-bahan kimia yang diperoleh daripada benda hidup manakala kimia tak organik dianggap sebagai cabang kimia yang mengkaji bahan-bahan kimia yang diperoleh daripada benda bukan hidup.
Kimia organik sebagai satu bidang sains dipersetujui umum sebagai bermula pada tahun 1828 dengan Friedrich Woehler mensistesis sebatian organik penting urea, secara tidak sengaja dengan menyejatkan larutan akueus ammonium cyanate (NH4OCN).

Mekanisme tindak balas[sunting | sunting sumber]

Tindak balas kimia sebatian organik boleh dikelaskan kepada tiga:
  • Penukargantian
  • Penambahan
  • Penyingkiran
Pengoksidaan, penurunan, dan penyusunan semula biasanya boleh diungkapkan sebagai kombinasi tiga tindak balas di atas.
For further details log on website :
https://ms.wikipedia.org/wiki/Kimia_organik
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KIMIA


Daripada Wikipedia, ensiklopedia bebas.
Kimia (Bahasa Inggeris: Chemistry) merupakan cabang sains yang berkenaan dengan komposisi, struktur, dan ciri jirim, dan juga perubahan yang dialami oleh jirim tersebut apabila didedahkan kepada jirim yang lain ataupun ketika berlaku perubahan keadaan fizikal di sekeliling jirim tersebut. Kimia merupakan sains fizikal yang melibatkan kajian pelbagai atom, molekul, hablur dan bentuk jirim lain baik diasingkan atau disebatikan, yang membabitkan konsep tenaga dan entropi berkenaan dengan kespontanan proses kimia.
Kimia dibahagikan kepada beberapa bahagian iaitu:
  1. kimia organik
  2. kimia tak organik
  3. kimia fizik
  4. kimia analisis
  5. biokimia
  6. kimia pengkomputan
Pelbagai bahagian baru seperti neurokimia telah wujud kebelakangan ini.
Kimia moden berkembang daripada ilmu alkimia semasa revolusi kimia 1773.

Sejarah kimia[sunting | sunting sumber]

Perkataan kimia berasal daripada perkataan Arab ‘al-kimiya’.Orang Yunani ialah bangsa pertama yang cuba menjelaskan mengapa berlaku perubahan kimia terjadi. Mereka telah mengemukakan suatu teori bahawa semua bahan terdiri daripada empat unsur asas iaitu api, air, tanah, dan udara 2400 tahun dahulu kala.
Keempat-empat unsur asas ini dipercayai saling berkaitan dan mempunyai ciri-ciri tertentu seperti sejuk, panas, kering, dan lembap. Teori ini dikemukakan kerana keempat-empat unsur itu amat penting dalam kehidupan seharian mereka pada masa itu.
Pada masa yang sama, orang-orang Mesir ketika itu, telah mengetahui cara-cara pengekstrakan logam-logam seperti emas, perak, besi, tembaga, dan timah. Istilah kimia juga berasal dari Mesir yang bermaksud tanah hitam dari Sungai Nil dalam bahasa Arab.
Asas kimia moden bermula pada abad ke-16 dengan perkembangan ilmu metalurgi ialitu pengekstrakan logam daripada bijihnya yang dilakukan oleh seorang berbangsa Jerman iaitu George Bauer, serta penggunaan mineral dalam ilmu perubatan oleh seorang yang berbangsa Switzerland iaitu bernama Paracelsus.
Robert Boyle (1627 – 1691) seorang ahli sains Inggeris dianggap sebagai pengasas kimia moden. Beliaulah orang yang pertama yang menjalankan eksperimen untuk mengkaji kesahan sesuatu pendapat yang dikemukan. Robert Boyle menghasilkan buku ‘The Sceptical Chymist’. Buku ini menerangkan sifat-sifat berlainan bagi unsur, sebatian, dan campuran dengan jelas.
Kimia merupakan satu cabang ilmu sains yang mengkaji bahan yang terdapat di dalam alam semesta serta perubahan yang berlaku ke atas bahan ini apabila berinteraksi antara satu sama lain. Perubahan-perubahan ini boleh dilihat dari segi tenaga, jisim, warna, dan sebagainya.
Oleh itu, ilmu kimia amat luas, daripada mengkaji zarah-zarah asas dalam sesuatu bahan hingga bagaimana bahan ini bertindak balas menghasilkan bahan yang baru. Ilmu kimia sering dianggap sebagai 'sains pusat' kerana kedudukannya yang unik dan bertindih dengan banyak cabang sains yang lain.

Kepentingan kimia[sunting | sunting sumber]

Memandangkan bahan kimia begitu mempengaruhi kehidupan kita, maka bidang kimia sudah pasti menjadi satu bidang kerjaya yang amat penting. Ahli kimia diperlukan dalam bidang pemakanan, perubatan, pertanian, serta dalam industri pembuatan.
Tanpa disedari atau sebaliknya, bahan kimia digunakan secara meluas dalam kehidupan seharian. Pakaian sutera atau kapas mahupun jaket nilon semuanya dibuat daripada bahan kimia.
Bahan makanan juga terdiri daripada bahan kimia. Protein, sebagai contoh, terdiri dari unsur-unsur karbon, hidrogen, oksigen dan nitrogen serta sedikit fosforus dan sulfur. Bahan kimia seperti glukosa dan sukrosa membekalkan tenaga kepada kita.
Industri kimia kian berkembang maju di Malaysia. Dalam pengeluaran minyak dan petrol, Malaysia merupakan Negara yang tersenarai sebagai Negara yang menjadi pengeluar utama di dunia.
Kegunaan bahan kimia akan terus meningkat dan manusia akan sentiasa memerlukan bahan baru. Di sinilah kimia memainkan peranan untuk menghasilkan benda baru.

Asas[sunting | sunting sumber]

Teori atom adalah asas kimia. Teori tersebut menyatakan bahawa semua jisim terbentuk daripada unit-unit kecil yang dikenali sebagai atom. Salah satu dari Hukum pertama dijumpai yang menjurus kepada penubuhan Kimia sebagai sains adalah Hukum Keabadian Jisim. Hukum itu menegaskan bahawa tidak terdapat perubahan yang boleh dikesan dalam kuantiti jisim ketika tindak balas kimia biasa berlaku. Fizik Moden sekarang menjelaskan bahawa atom dan tenaga tidak boleh dicipta atau dimusnahkan dalam satu tindak balas kimia. Secara kasarnya suatu tindak balas yang bermula dengan 1001 atom akan berakhir dengan 1001 atom juga, walau banyak mana sekalipun tindak balas yang terjadi. Walaupun awalnya sesuatu itu hijau dan berlendir dan menjadi sesuatu yang keras dan hitam sesudah tindak balas, jumlah atom akan masih kekal.
Jisim juga sama sekiranya tenaga yang dibebaskan atau ditambah diambil kira. Ahli kimia mengkaji interaksi atom ini secara individual dan kadang kala dengan sebatian atom lain untuk membentuk ion dan molekul. Atom-atam ini bergabung dengan atom lain (sebagai contoh, kayu terbakar adalah gabungan oksigen dari udara dengan atom karbon dan hidrogen dalam kayu dan mereka juga berinteraksi dengan cahaya manakala gambar terbentuk akibat perubahan kimia atas filem yang disebabkan oleh cahaya) dan radiasi lain. Salah satu jumpaan awal yang menakjubkan adalah atom-atom ini sentiasa bergabung dalam nisbah sekata: struktur pasir silika mempunyai nisbah atom silika dengan oksigen pada 1 : 2. Kita sekarang mengetahui bahawa terdapat pengecualian dalam Hukum Perkadaran Tetap (Law of Definite Proportions). Litar sepadu (integrated circuits) adalah contoh aplikasi hukum ini yang baik.
Satu lagi penemuan yang penting dalam kimia adalah apabila perubahan berlaku, jumlah tenaga yang terhasil atau hilang sentiasa sama. Ini mendorong kepada konsep penting pada keseimbangan, termodinamik, dan kinetik. Teori paling menarik yang menggambarkan semua kimia adalah Kuantum Mekanik (Quantum Mechanics). Teori ini kompleks, susah difahami, dan sukar dimahiri. konsep yang lebih mudah difahami adalah konsep yang diambil dari kimia asid dan bes (acid/base chemistry). Konsep ini terhad skopnya tetapi lebih mudah difahami dan dipakai. Sering kali penemuan kimia dibuat oleh pakar fizik, biologi, jurutera kimia atau farmasi.
For further details log on website :
https://ms.wikipedia.org/wiki/Kimia
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10 Basic Chemistry Facts

Author
by Anne Marie Helmenstine, Ph.D.

Fun and Interesting Chemistry Facts

This is a collection of 10 fun and interesting basic chemistry facts.
  1. 1) Chemistry is the study of matter and energy and the interactions between them. It is a physical science that is closely related to physics, which often shares the same definition.
  2. 2) Chemistry traces its roots back to the ancient study of alchemy. Chemistry and alchemy are separate now, though alchemy still is practiced today.
  3. 3) All matter is made up of the chemical elements, which are distinguished from each other by the numbers of protons they possess.
  4. 4) The chemical elements are organized in order of increasing atomic number into the periodic table. The first element in the periodic table is hydrogen.
  5. 5) Each element in the periodic table has a one or two-letter symbol. The only letter in the English alphabet not used on the periodic table is J. The letter q only appears in the symbol for the placeholder name for element 114, ununquadium, which has the symbol Uuq. When element 114 is officially discovered, it will be given a new name.
  6. 6) At room temperature, there are only two liquid elements. These are bromineand mercury.
  7. 7) The IUPAC name for water, H2O, is dihydrogen monoxide.
  8. 8) Most elements are metals and most metals are silver-colored or gray. The only non-silver metals are gold and copper.
  9. 9) The discoverer of an element may give it a name. There are elements named for people (Mendelevium, Einsteinium), places (Californium, Americium) and other things.
  10. 10) Although you may consider gold to be rare, there is enough gold in the Earth's crust to cover the land surface of the planet knee-deep.
For further details log on website :
https://www.thoughtco.com/basic-chemistry-facts-607560
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GENERAL CHEMISTRY

Requirements

What you need to know

Dartmouth's Department of Chemistry offers two separate sequences in general chemistry. A majority of our students are enrolled in Chemistry 5-6. In addition, there is a fall-term honors section, Chemistry 10, available only to especially well-prepared First Year students.
Each year we enroll quite a number of students who have not had high school chemistry or who feel that their high school chemistry backgrounds are weak. It is most certainly possible for such students to do well in general chemistry at Dartmouth. However, many of them find it helpful to study and review in preparation for the course. This page will tell you what you need to learn or review to be off to a flying start in general chemistry.

A Self Test

If you would like to try a few real-world problems to measure your preparation and skills in the fundamental areas discussed in more detail below, please feel free to download the Chemistry 5 Self Test (a 3-page pdf file). This test (which carries neither credit nor penalty) is entirely for your private use. It has ten straighforward problems spread across the topics listed below. Work your way through it at your own pace, but try to solve each problem without consulting any other reference. Once you have come up with your best answers to these problems (or have decided that you cannot work one or more problems on your own), then, and only then, you should download the 9-page pdf Self Test Solutions, which gives fairly detailed, step-by-step answers to each of these problems. The page on this site titled Dimensional Analysis and Units will also provide some review on those topics, and your course text probably has helpful sections as well.
There is no "passing or failing grade" on this test. Rather, it is meant to show you what areas you may need to review, study in more depth, or continue to practice.

The Important Basic Topics

Listed below are some of the more important topics that you should be familiar with. You may, of course, review or study as much as you like, but you are encouraged to concentrate on and become familiar with the following topics:
1. Metric System. Be familiar with the units of mass, length, and volume in the metric system. A separate page covers this important topic.
2. Temperature Scales. Be familiar with the Celsius (centigrade) and the kelvin (absolute) temperature scales.
3. Symbols of the Elements. You should be familiar with the symbols for elements with atomic numbers 1-38, 46-56, and 78-83. The symbols are usually abbreviations of either the English or Latin name of the element. Although you will have a periodic table for all exams, the more familiar you are with the symbols, the better off you will be.
4. Chemical Formulas. You should become familiar with the way in which the symbols of elements are combined to give chemical formulas for neutral (uncharged) molecules and positive or negative ions, such as SiCl4, CaF2, SO4-2, etc.
5. Chemical Equations. You should understand how chemical formulas are combined to give chemical equations, which describe chemical changes.
6. Atomic Structure. You should have at least a rough idea of the structure of the atom. Be aware that the nucleus, composed of protons and neutrons, is the massive (but tiny) positively charged central core of the atom. It is surrounded by one or more negatively charged electrons which occupy most of the volume of the atom but contribute only a tiny fraction of its mass. You should also know what isotopes are.
7. Weight Relationships. You should know what atomic number, atomic mass number, atomic weight, formula weight, and molecular weight mean. Understand what gram atomic weight, gram formula weight, and gram molecular weight mean. Know what is meant by a mole of a substance, and understand the relationship between the mole and Avogadro's constant.
8. Concepts from Physics. Have some notion of the meaning of force and energy and the units in which they are measured in the Standard International (SI) system of units. Pressure is a measure of force per unit area; common units of pressure are pascal (Pa), atmosphere (atm), and torr (Torr).
9. Concentrations. Know some common ways of expressing concentration, such as weight percent and moles of solute per liter of solution (molarity).
Review these topics, and check out the page covering Dimensional Analysis and Units.
A review of certain topics in high school mathematics will also be valuable to any student in college chemistry. Listed below are some of the topics with which you should be quite comfortable. The last two, numbers 6 and 7, apply more to Chem 6 than Chem 5.
1. Calculators. You must have a calculator and know how to use it for multiplication, division, taking square roots, finding logarithms and antilogarithms (both base-10 and natural, or base-e, logs), and using exponential notation.
2. Exponential Notation. Be thoroughly familiar with exponents, and be able to multiply, divide, raise to powers, and take roots of numbers with exponents. Understand the relationship between exponents and logarithms, and be able to work with logarithms, both base 10 and base e. Know the SI prefixes for common multiples of powers of 10, such as "m" for "milli-" or "k" for "kilo-" and so forth.
3. Linear Equations. Be able to recognize an equation for a straight line, and know how to recognize the line's slope and intercept in the equation.
4. Algebra. Be able to solve a system of two simultaneous linear equations in two unknowns.
5. More Algebra. Be able to solve a quadratic equation.
6. Trigonometry. Be familiar with angles measured in radians as well as in degrees, and understand and be able to work with the basic trigonometric functions: sine, cosine, and tangent.
7. Coordinate Systems. Be familiar with polar coordinate systems in two and three dimensions as well as the common Cartesian (x,y) coordinate system.
Many of the definitions and concepts mentioned above will be reviewed quickly during the initial weeks of Chemistry 5. However, it will be to your advantage to have seen such material and thought about it in advance. You will also find most of these topics are included in the first chapters or appendices of your textbook. If you find that the text selected for your course assumes too much previous knowledge, try reading another textbook. Instructors generally make a variety of books available at the reserve desk at Kresge Library, and you may find one that is more clear to you, especially if you have not previously studied chemistry at this depth before.
For further details log on website :
https://www.dartmouth.edu/~genchem/know.html
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The Chemistry of Life: The Human Body

Author
By 
Editor's Note: This occasional series of articles looks at the vital things in our lives and the chemistry they are made of.

You are what you eat. But do you recall munching some molybdenum or snacking on selenium? Some 60 chemical elements are found in the body, but what all of them are doing there is still unknown.

Roughly 96 percent of the mass of the human body is made up of just four elements: oxygen, carbon, hydrogen and nitrogen, with a lot of that in the form of water. The remaining 4 percent is a sparse sampling of the periodic table of elements.
Some of the more prominent representatives are called macro nutrients, whereas those appearing only at the level of parts per million or less are referred to as micronutrients.

These nutrients perform various functions, including the building of bones and cell structures, regulating the body's pH, carrying charge, and driving chemical reactions.

The FDA has set a reference daily intake for 12 minerals (calcium, iron, phosphorous, iodine, magnesium, zinc, selenium, copper, manganese, chromium, molybdenum and chloride). Sodium and potassium also have recommended levels, but they are treated separately.

However, this does not exhaust the list of elements that you need. Sulfur is not usually mentioned as a dietary supplement because the body gets plenty of it in proteins.

And there are several other elements — such as silicon, boron, nickel, vanadium and lead — that may play a biological role but are not classified as essential.

"This may be due to the fact that a biochemical function has not been defined by experimental evidence," said Victoria Drake from the Linus Pauling Institute at Oregon State University.

Sometimes all that is known is that lab animals performed poorly when their diets lacked a particular non-essential element. However, identifying the exact benefit an element confers can be difficult as they rarely enter the body in a pure form.

"We don't look at them as single elements but as elements wrapped up in a compound," said Christine Gerbstadt, national spokesperson for the American Dietetic Association.

A normal diet consists of thousands of compounds (some containing trace elements) whose effects are the study of ongoing research. For now, we can only say for certain what 20 or so elements are doing. Here is a quick rundown, with the percentage of body weight in parentheses.

Oxygen (65%) and hydrogen (10%) are predominantly found in water, which makes up about 60 percent of the body by weight. It's practically impossible to imagine life without water.

Carbon (18%) is synonymous with life. Its central role is due to the fact that it has four bonding sites that allow for the building of long, complex chains of molecules. Moreover, carbon bonds can be formed and broken with a modest amount of energy, allowing for the dynamic organic chemistry that goes on in our cells.

Nitrogen (3%) is found in many organic molecules, including the amino acids that make up proteins, and the nucleic acids that make up DNA.

Calcium (1.5%) is the most common mineral in the human body — nearly all of it found in bones and teeth. Ironically, calcium's most important role is in bodily functions, such as muscle contraction and protein regulation. In fact, the body will actually pull calcium from bones (causing problems like osteoporosis) if there's not enough of the element in a person's diet.

Phosphorus (1%) is found predominantly in bone but also in the molecule ATP, which provides energy in cells for driving chemical reactions.

Potassium (0.25%) is an important electrolyte (meaning it carries a charge in solution). It helps regulate the heartbeat and is vital for electrical signaling in nerves.

Sulfur (0.25%) is found in two amino acids that are important for giving proteins their shape.

Sodium (0.15%) is another electrolyte that is vital for electrical signaling in nerves. It also regulates the amount of water in the body.

Chlorine (0.15%) is usually found in the body as a negative ion, called chloride. This electrolyte is important for maintaining a normal balance of fluids.

Magnesium (0.05%) plays an important role in the structure of the skeleton and muscles. It also is necessary in more than 300 essential metabolic reactions.

Iron (0.006%) is a key element in the metabolism of almost all living organisms. It is also found in hemoglobin, which is the oxygen carrier in red blood cells. Half of women don't get enough iron in their diet.

Fluorine (0.0037%) is found in teeth and bones. Outside of preventing tooth decay, it does not appear to have any importance to bodily health.

Zinc (0.0032%) is an essential trace element for all forms of life. Several proteins contain structures called "zinc fingers" help to regulate genes. Zinc deficiency has been known to lead to dwarfism in developing countries.

Copper (0.0001%) is important as an electron donor in various biological reactions. Without enough copper, iron won't work properly in the body.

Iodine (0.000016%) is required for making of thyroid hormones, which regulate metabolic rate and other cellular functions. Iodine deficiency, which can lead to goiter and brain damage, is an important health problem throughout much of the world.

Selenium (0.000019%) is essential for certain enzymes, including several anti-oxidants. Unlike animals, plants do not appear to require selenium for survival, but they do absorb it, so there are several cases of selenium poisoning from eating plants grown in selenium-rich soils.

Chromium (0.0000024%) helps regulate sugar levels by interacting with insulin, but the exact mechanism is still not completely understood.

Manganese (0.000017%) is essential for certain enzymes, in particular those that protect mitochondria — the place where usable energy is generated inside cells — from dangerous oxidants.

Molybdenum (0.000013%) is essential to virtually all life forms. In humans, it is important for transforming sulfur into a usable form. In nitrogen-fixing bacteria, it is important for transforming nitrogen into a usable form.

Cobalt (0.0000021%) is contained in vitamin B12, which is important in protein formation and DNA regulation.
For further details log on website :
http://www.livescience.com/3505-chemistry-life-human-body.html
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Advantages and Disadvantages of Fasting for Runners

Author BY   ANDREA CESPEDES  Food is fuel, especially for serious runners who need a lot of energy. It may seem counterintuiti...