Photosynthesis is a process in which chlorophyll traps and uses energy from the sun in the form of light. Six molecules of carbon dioxide combine with six molecules of water to form one molecule of glucose sugar. The glucose molecule consists of six atoms of carbon, twelve of hydrogen, and six of oxygen. Six oxygen molecules, consisting of two oxygen atoms each, are also produced and are discharged into the atmosphere unless the plant needs energy to live. In that case, the oxygen combines with the glucose immediately, releasing six molecules of carbon dioxide and six of water for each molecule of glucose Beggott The carbon cycle is then completed as the plant obtains the energy that was stored by the glucose.
The length of time required to complete the cycle varies. In plants without an immediate need for energy, the chemical processes continue in a variety of ways.
By reducing the hydrogen and oxygen content of most of the sugar molecules by one water molecule and combining them to form large molecules, plants produce substances such as starch, inulin , and fats and store them for future use. Regardless of whether the stored food is used later by the plant or consumed by some other organism, the molecules will ultimately be digested and oxidized, and carbon dioxide and water will be discharged. Other molecules of sugar undergo a series of chemical changes and are finally combined with nitrogen compounds to form protein substances, which are then used to build tissues WWW 2.
Although protein substances may pass from organism to organism, eventually these too are oxidized and form carbon dioxide and water as cells wear out and are broken down, or as the organisms die.
In either case, a new set of organisms, ranging from fungi to the large scavengers, use the waste products or tissues for food, digesting and oxidizing the substances for energy release WWW 1. The carbon cycle, temporarily interrupted in this manner, is completed as fuels are burned, and carbon dioxide and water are again added to the atmosphere for reuse by living things, and the solar energy stored by photosynthesis ages ago is released Kinoshita Almost everything around us today has some connection with carbon or a carbon compound.
Carbon is in every living organism. Without carbon life would not exist as we know it. If we have helped you, please help us fix his smile with your old essays Tutor and Freelance Writer. Science Teacher and Lover of Essays. Article last reviewed: St. Skip to content. Carbon: History, Uses, Occurrence. Find out More.
And it dawned on Willard Libby of Chicago University that the radioactivity generated by carbon could be exploited to tremendous advantage. A chemist who had worked on the Manhattan Project to build the first atom bomb, Libby realised that when an organism dies, it will stop absorbing carbon, including carbon, and its existing store of the latter will slowly decay.
So, by measuring the radioactivity of a sample taken from the organism, its carbon content could be estimated and the date of its time of death could be measured. The sciences of archaeology and palaeontology were about to be revolutionised. A major problem had to be overcome, however. Carbon exists in only very low levels in the tissue of recently deceased animals and plants: about one in a trillion of their carbon atoms are carbon By contrast, natural background radiation — from thorium and uranium in rocks and other sources — is much, much higher.
Libby solved the problem by carefully shielding his detectors and developing ways to tune out any radiation that made it through to the walls of his device. Then he turned to the gas methane, which contains carbon, to provide final validation of his technique, comparing samples from two very different sources. One sample was extracted from natural gas, a fossil fuel whose carbon should have decayed long ago. The second came from the city of Baltimore sewerage system and was extracted from human excrement.
It should be rich in carbon, having just been produced by humans, Libby reasoned. And that is exactly what he found.
Ancient methane had no carbon By contrast, methane newly excreted by humans was relatively rich in the isotope. His results perfectly matched the known dates of the items he had scanned. It was a brilliant undertaking for which Libby was awarded the Nobel prize for chemistry in , though he was lucky in one sense.
Libby assumed that the rate of carbon production in the atmosphere had been constant for the past few tens of thousands of years. In fact, it has varied fairly widely, thanks to changes in sunspot activity, atmospheric nuclear bomb tests and rising emissions of carbon dioxide from fossil fuels. These have to be taken carefully into account when estimating ages, scientists now realise, though the underlying basis of radiocarbon dating remains sound.
More recently, radiocarbon dating has changed from simply measuring the radioactivity emitted by carbon nuclei to directly counting numbers of atoms of the isotope in a sample. This is done using a technique called accelerator mass spectrometry AMS , which has allowed scientists to date bones, artefacts and other carbon-based items from the tiniest sample. One example involving the use of carbon resulted in the overturning of the idea that past western European cultures had depended on practices and ideas that began in the Middle East and slowly disseminated westwards with the spread of farming.
Radiocarbon dating revealed a very different picture and showed that the neolithic cultures of Britain, France and central Europe must have evolved independently. Later, the technique was used by laboratories in Britain, Switzerland and the United States to date the flax used to weave the Turin shroud. Oxidation states and isotopes. Glossary Data for this section been provided by the British Geological Survey.
Relative supply risk An integrated supply risk index from 1 very low risk to 10 very high risk. Recycling rate The percentage of a commodity which is recycled. Substitutability The availability of suitable substitutes for a given commodity. Reserve distribution The percentage of the world reserves located in the country with the largest reserves. Political stability of top producer A percentile rank for the political stability of the top producing country, derived from World Bank governance indicators.
Political stability of top reserve holder A percentile rank for the political stability of the country with the largest reserves, derived from World Bank governance indicators. Supply risk. Coal Diamond Graphite Coal. Relative supply risk 4. Relative supply risk 6. Relative supply risk 8. Young's modulus A measure of the stiffness of a substance.
Shear modulus A measure of how difficult it is to deform a material. Bulk modulus A measure of how difficult it is to compress a substance. Vapour pressure A measure of the propensity of a substance to evaporate. Pressure and temperature data — advanced. Listen to Carbon Podcast Transcript :. You're listening to Chemistry in its element brought to you by Chemistry World , the magazine of the Royal Society of Chemistry.
Hello, this week to the element that unites weddings, wars, conflicts and cremations and to explain how, here's Katherine Holt. Any chemist could talk for days about carbon. It is after all an everyday, run-of-the-mill, found-in-pretty-much-everything, ubiquitous element for us carbon-based life forms. An entire branch of chemistry is devoted to its reactions.
In its elemental form it throws up some surprises in the contrasting and fascinating forms of its allotropes. It seems that every few years a new form of carbon comes into fashion - A few years ago carbon nanotubes were the new black or should I say 'the new bucky-ball' - but graphene is oh-so-now! But today I'm going to talk about the most glamorous form that carbon can take - diamond. For millennia diamond has been associated with wealth and riches, as it can be cut to form gemstones of high clarity, brilliance and permanence.
Diamonds truly are forever! Unfortunately, diamond also has a dark side - the greed that diamond induces leads to the trade of so-called 'conflict diamonds' that support and fund civil wars. Mans desire for diamond has led alchemists and chemists over many centuries to attempt to synthesise the material. After many fraudulous early claims diamond was finally synthesised artificially in the s.
Scientists took their inspiration from nature by noting the conditions under which diamond is formed naturally, deep under the earth's crust. This was an impressive feat, but the extreme conditions required made it prohibitively expensive as a commercial process. Since then the process has been refined and the use of metal catalysts means that lower temperatures and pressures are required.
Crystals of a few micron diameter can be formed in a few minutes, but a 2-carat gem quality crystal may takes several weeks.
These techniques mean its now possible to artificially synthesise gemstone quality diamonds which, without the help of specialist equipment, cannot be distinguished from natural diamond. It goes without saying that this could cause headaches among the companies that trade in natural diamond! It is possible to turn any carbon based material into a diamond - including hair and even cremating remains! Yes - you can turn your dearly departed pet into a diamond to keep forever if you want to!
Artificial diamonds are chemically and physical identical to the natural stones and come without the ethical baggage. However, psychologically their remains a barrier - if he really loves you he'd buy you real diamond - wouldn't he? From the perspective of a chemist, materials scientist or engineer we soon run out of superlatives while describing the amazing physical, electronic and chemical properties of diamond.
It is the hardest material known to man and more or less inert - able to withstand the strongest and most corrosive of acids. It has the highest thermal conductivity of any material, so is excellent at dissipating heat. That is why diamonds are always cold to the touch. Having a wide band gap, it is the text book example of an insulating material and for the same reason has amazing transparency and optical properties over the widest range of wavelengths of any solid material.
You can see then why diamond is exciting to scientists. Its hardness and inert nature suggest applications as protective coatings against abrasion, chemical corrosion and radiation damage.
Its high thermal conductivity and electrical insulation cry out for uses in high powered electronics. Its optical properties are ideal for windows and lenses and its biocompatibility could be exploited in coatings for implants. These properties have been known for centuries - so why then is the use of diamond not more widespread?
The reason is that natural diamond and diamonds formed by high pressure high temperature synthesis are of limited size - usually a few millimeters at most, and can only be cut and shaped along specific crystal faces. This prevents the use of diamond in most of the suggested applications. However, about 20 years ago scientists discovered a new way to synthesise diamond this time under low pressure, high temperature conditions, using chemical vapour deposition.
If one were to consider the thermodynamic stability of carbon, we would find that at room temperature and pressure the most stable form of carbon is actually graphite, not diamond. Strictly speaking, from a purely energetic or thermodynamic point of view, diamond should spontaneously turn into graphite under ambient conditions!
Clearly this doesn't happen and that is because the energy required to break the strong bonds in diamond and rearrange them to form graphite requires a large input of energy and so the whole process is so slow that on the scale of millennia the reaction does not take place.
It is this metastability of diamond that is exploited in chemical vapour deposition. The carbon-based molecules then deposit on a surface to form a coating or thin film of diamond. Actually both graphite and diamond are initially formed, but under these highly reactive conditions, the graphitic deposits are etched off the surface, leaving only the diamond.
The films are polycrystalline, consisting of crystallites in the micron size range so lack the clarity and brilliance of gemstone diamond. While they may not be as pretty, these diamond films can be deposited on a range of surfaces of different size and shapes and so hugely increase the potential applications of diamond. Challenges still remain to understand the complex chemistry of the intercrystalline boundaries and surface chemistry of the films and to learn how best to exploit them.
This material will be keeping chemists, materials scientists, physicists and engineers busy for many years to come. However, at present we can all agree that there is more to diamond than just a pretty face! Katherine Holt extolling the virtues of the jewel in carbon's crown. Next week we're heading to the top of group one to hear the story of the metal that revolutionised the treatment of manic depression. Its calming effect on the brain was first noted in , by an Australian doctor, John Cade, of the Victoria Department of Mental Hygiene.
He had injected guinea pigs with a 0. Cade then gave his most mentally disturbed patient an injection of the same solution. The man responded so well that within days he was transferred to a normal hospital ward and was soon back at work. And it's still used today although despite 50 years of medical progress we still don't know how it works. That was Matt Wilkinson who will be here with the story of Lithium on next week's Chemistry in its Element, I do hope you can join us.
I'm Chris Smith, thank you for listening and goodbye. Chemistry in its element is brought to you by the Royal Society of Chemistry and produced by thenakedscientists. There's more information and other episodes of Chemistry in its element on our website at chemistryworld. Click here to view videos about Carbon. View videos about. Help Text. Learn Chemistry : Your single route to hundreds of free-to-access chemistry teaching resources. We hope that you enjoy your visit to this Site.
We welcome your feedback. Data W. Haynes, ed. Version 1. Coursey, D. Schwab, J. Tsai, and R. Dragoset, Atomic Weights and Isotopic Compositions version 4. Periodic Table of Videos , accessed December Podcasts Produced by The Naked Scientists.
Download our free Periodic Table app for mobile phones and tablets. Explore all elements. D Dysprosium Dubnium Darmstadtium.
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