WHY GRAPHITE IS SOFT BUT DIAMOND IS SO HARD - Diamond and graphite are two allotropes of the same element (carbon) and the differences in their properties are a result of the way their crystal structures are arranged. Both diamond and graphite are made of pure carbon, yet they have dramatic differences in their properties. As allotropes of the same element, you might expect them to share many similarities, but that simply isn’t the case. Allotropy (also referred to as ‘allotropism’) of an element is that element’s ability to exist in multiple forms in the same physical state with a different arrangement of its atoms. The different forms are called allotropes of the given chemical element. Allotropes of the same element have different bonding arrangements, which give rise to different chemical and physical properties for the substance. Furthermore, different allotropes can also differ in the occurrence of molecules in the number of atoms. Carbon has the ability to form many allotropes, thanks to its chemical structure. Its atomic number is 6, which means that it has 4 electrons in its valence shell. No less than 8 allotropes of carbon have been identified. Out of all the known allotropes, the most popular ones are diamond and graphite. Although their composition is the same, they exhibit different chemical and physical properties, thanks to the arrangement of carbon atoms within them. It boils down to a single factor: geometry. The arrangement of carbon atoms in diamond follows a tetrahedral fashion. This means that each carbon atom is attached to 4 other carbon atoms, forming strong covalent bonds.

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Why Is Graphite Soft, But Diamond Is So Hard?

By Ashish

Diamond and graphite are two allotropes of the same element (carbon) and the differences in their properties are a result of the way their crystal structures are arranged.

Both diamond and graphite are made of pure carbon, yet they have dramatic differences in their properties.

As allotropes of the same element, you might expect them to share many similarities, but that simply isn’t the case.

At first, this question might seem odd to many people. Diamond and graphite… doesn’t sound like a particularly sensible combination.

Diamond and gold, or diamond and sapphire would make more sense, right?

So, why is diamond pitted in the same category with graphite – the thing that we find inside our pencils?

Well, if you had paid attention to your Chemistry lessons in high school, you would know that there is, in fact, a very strong structural connection between the two.

What’s the connection between the two? And why are they so different from each other?

What are allotropes?

Allotropy (also referred to as ‘allotropism’) of an element is that element’s ability to exist in multiple forms in the same physical state with a different arrangement of its atoms.

The different forms are called allotropes of the given chemical element.

Triangle Rectangle & square shapes 36 ball

Imagine that you have 36 balls that you can arrange in any number of patterns to obtain mutually-visually geometrical shapes.

The constituent pieces of these shapes (balls) represent atoms, and the different shapes they assume (due to their varied arrangements) are the allotropes.

Allotropes of the same element have different bonding arrangements, which give rise to different chemical and physical properties for the substance.

Allotropes of Phosphorus & Allotropes of Oxygen

Furthermore, different allotropes can also differ in the occurrence of molecules in the number of atoms.

The following image features various allotropes of phosphorus and oxygen.

Allotropes of carbon

In the world of allotropes, the carbon is nothing less than a rockstar. It has the ability to form many allotropes, thanks to its chemical structure.

Its atomic number is 6, which means that it has 4 electrons in its valence shell.

Different allotropes of carbon

As of now, no less than 8 allotropes of carbon have been identified, and the research for discovering even more allotropes is on.

However, out of all the known allotropes, the most popular ones are diamond and graphite.

These two allotropes, which visually appear incredibly different, are still made of nothing but carbon.

Although their composition is the same, they exhibit different chemical and physical properties, thanks to the arrangement of carbon atoms within them.

Why is diamond hard, but graphite is soft, despite being composed of the same element (carbon)?

It boils down to a single factor: geometry.

Diamond Structure

The arrangement of carbon atoms in diamond follows a tetrahedral fashion. This means that each carbon atom is attached to 4 other carbon atoms, forming strong covalent bonds.

This crystal arrangement is energetically very favorable and imparts that characteristic strength, durability and rigidity to diamond.

To scratch or break it requires a high amount of force, which makes it one of the hardest naturally-occurring materials on the planet.

Graphite, on the other hand, has an entirely different geometric arrangement than diamond.

Its carbon atoms are arranged in 2D sheets, whereas each carbon atom is bonded to three other carbon atoms to form hexagonal rings in an infinite array.

graphite-structure

Although the bonding of atoms within each individual layer is covalent and therefore quite strong (as strong as is seen in diamond), the bonding between layers is weak (Van der Waals forces).

The result of this is that the layers slide over each and can detach from each other very easily.

These weak bonds between the multiple sheets of carbon atoms make the graphite used in pencils flake off on paper, allowing you to write.

In addition to being soft and slippery, graphite also has a much lower density than diamond.

The one thing about all of this that amazes me most is how a few tweaks in the chemical structure of identical substances make them so massively different in their appearance, toughness and chemical properties!

Ashish is a Science graduate (Bachelor of Science) from Punjabi University (India). He spends a lot of time watching movies, and an awful lot more time discussing them. He likes Harry Potter and the Avengers, and obsesses over how thoroughly Science dictates every aspect of life… in this universe, at least.

https://www.scienceabc.com/pure-sciences/graphite-soft-diamond-structure-properties-hard-carbon-allotrope-tetrahedral-layers.html
 

GRAPHENE - 200 Times Stronger Than Steel, 1,000 Times Lighter Than Paper - A sheet of graphene looks like an atomic-scale honeycomb. Measuring in at just one atom thick, a sheet of graphene checks all the boxes of a supermaterial: Graphene is 200 times stronger than steel by weight; It is 1,000 times lighter than paper; It is 98 percent transparent; It conducts electricity better than any other known material at room temperature; It can convert light at any wavelength into a current; And, last but not least, graphene is made from carbon, the fourth most-abundant element in the universe, so we're not likely to run out. Graphene gets its superpowers from its structure. If you could zoom in close enough, you'd see that a sheet of graphene looks like an atomic-scale honeycomb. Individual carbon atoms are arranged in a hexagonal pattern that resembles chicken wire. Each carbon atom in a sheet of graphene is covalently bonded to three other carbon items, which gives the material its incredible strength. Why does graphene conduct electricity so well? Again, because of the way those carbon atoms are bonded. Each carbon atoms has four electrons in its outer shell, but only three of those electrons are shared with its neighboring three carbon atoms. The remaining electron is called a pi electron and is free to move in three-dimensional space, which allows it to transmit electrical charges across the sheet of graphene with almost no resistance.

A sheet of graphene looks like an atomic-scale honeycomb.

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Graphene

200 Times Stronger Than Steel, 1,000 Times Lighter Than Paper

BY DAVE ROOS

In 2004, two scientists at the University of Manchester conducted a deceptively simple experiment with potentially world-changing consequences.

The researchers, Andre Geim and Konstantin Novoselov, were playing around with graphite, the stuff in the tip of your pencil.

Graphite is made of super-thin sheets of pure carbon stacked on top of each other.

Geim and Novoselov wanted to see if they could isolate a single sheet of graphite, an impossibly thin layer of carbon measuring just one atom thick.

So, they grabbed a roll of sticky tape. Yes, the same transparent tape in the plastic applicator that you keep in your junk drawer.

Here's how Geim described his technique, as reported by the BBC.

"You put [sticky tape] on graphite or mica and peel the top layer. There are flakes of graphite that come off on your tape. Then you fold the tape in half and stick it to the flakes on top and split them again. And you repeat this procedure 10 or 20 times. Each time, the flakes split into thinner and thinner flakes. At the end you're left with very thin flakes attached to your tape. You dissolve the tape and everything goes into solution."

The sticky-tape method worked!

By isolating a single-layer sheet of carbon, Geim and Novoselov were credited with discovering a brand-new material called graphene that's now believed to be the strongest, lightest and most electrically conductive substance on Earth.

In 2010, Geim and Novoselov shared the Nobel Prize in physics for discovering graphene, and researchers around the world began clamoring for ways to use this remarkable "supermaterial" to build more powerful and longer-lasting batteries, faster microchips, flexible circuitry, implantable biosensors and more.

A decade later, graphene has yet to deliver on its much-hyped promises, but insiders are confident that we'll finally be seeing smartphones, electric cars and sensors using graphene-based technology in the next few years.

Why Is Graphene a Supermaterial?

Measuring in at just one atom thick, a sheet of graphene checks all the boxes of a supermaterial:

o  Graphene is 200 times stronger than steel by weight.

o  It is 1,000 times lighter than paper.

o  It is 98 percent transparent.

o  It conducts electricity better than any other known material at room temperature.

o  It can convert light at any wavelength into a current.

o  And, last but not least, graphene is made from carbon, the fourth most-abundant element in the universe, so we're not likely to run out

Graphene gets its superpowers from its structure.

If you could zoom in close enough, you'd see that a sheet of graphene looks like an atomic-scale honeycomb.

Individual carbon atoms are arranged in a hexagonal pattern that resembles chicken wire.

Each carbon atom in a sheet of graphene is covalently bonded to three other carbon items, which gives the material its incredible strength.

Why does graphene conduct electricity so well?

Again, because of the way those carbon atoms are bonded.

At Cabot Corporation, senior researcher Matt Hesketh examines the progression
 of graphene in three vials. The vial on the left is graphite, the middle one
is graphite expanded, and the one on the right is graphene.

Each carbon atoms has four electrons in its outer shell, but only three of those electrons are shared with its neighboring three carbon atoms.

The remaining electron is called a pi electron and is free to move in three-dimensional space, which allows it to transmit electrical charges across the sheet of graphene with almost no resistance. In fact, graphene is the fastest conductor of electricity at room temperature of any known substance.

The 'Magic Angle'

A recent discovery may add yet another superpower to graphene's brag list.

A team at Massachusetts Institute of Technology (MIT) was experimenting with dual-layered graphene — two layers of single-atom graphene stacked together — when they stumbled upon a new, nearly magical property of graphene.

When the layers are rotated slightly out of line with each other — a displacement of exactly 1.1 degrees — the graphene becomes a superconductor.

Superconductors are the rarest class of materials that conduct electricity with absolutely no resistance and zero heat.

The discovery of graphene's "supermaterial" sent shockwaves through the scientific community.

Although the experiment was conducted at extreme low temperatures (close to 0 degrees Kelvin or minus 459.67 F), it opened up the possibility that by combining graphene with other superconductive elements, we're closer than ever to room-temperature superconductivity.

Such an achievement would radically improve the energy efficiency of everything from gadgets to cars to entire electric grids.

How Might Graphene Transform Technology?

Superconductivity is still decades away, but revolutionary graphene-based products are coming to the market much sooner, says Andrea Ferrari, a professor of nanotechnology and director of the Cambridge Graphene Centre.

"By 2024, there will be a variety of graphene products on the market," says Ferrari, "including batteries, photonics, night vision cameras and more."

Consumers have been eagerly awaiting graphene-based batteries for years.

The lithium-ion batteries in all our gadgets are relatively slow to charge, lose their juice quickly and burn out after a set number of cycles.

That's because the electrochemical process that powers lithium-ion batteries generates a lot of heat.

But since graphene is the world's most efficient electrical conductor, it produces a lot less heat when charging up or discharging electricity.

Graphene-based batteries are promising five times faster charging speeds than lithium-ion, three times longer battery life, and five times as many cycles before they need to be replaced.

Electronics companies like Samsung and Huwei are actively developing graphene-based batteries for smartphones and other gadgets, but the earliest those will hit the market is 2021.

As for graphene batteries in electric cars — which could dramatically increase their driving radius — that's still a few years off.

An entire industry has been built on lithium-ion technology and it won't change overnight.

"The battery industry is very conservative," says Jesus de la Fuente, CEO of Graphanea, a company that manufactures and sells pure graphene and graphene-based chips to academic researchers and R&D departments.

"It might change the composition of batteries a few times every five to ten years, which makes it very difficult to introduce new products in this industry."

There are a few graphene-based batteries on the market, including some wired and wireless chargers from a company called Real Graphene, but those are only the tip of the iceberg, says Ferrari, who is also the science and technology officer for the Graphene Flagship, a 1-billion-euro collaboration by the European Union to speed the development of graphene technology.

Research partners with the Flagship are already making graphene batteries that outperform today's best high-energy cells by 20 percent capacity and 15 percent energy.

Other teams have built graphene-based solar cells that are 20 percent more efficient at converting sunlight to electricity.

Other Uses for Graphene

While graphene batteries might be first to market, researchers are busy developing countless other applications for this miracle material.

Biosensors are a big deal. Imagine an incredibly thin and flexible chip that can be injected into the bloodstream to monitor real-time health data like insulin levels or blood pressure.

Physics professor Dr. Yan Fung, holds a new invention of low-cost
semitransparent solar cells with graphene electrodes
at Poly University in Hung Hom, China, 2015.

Or a graphene interface that sends signals back and forth to the brain to detect an upcoming epileptic seizure or even prevent it.

Thin, stretchable sensors can also be worn on the skin or woven into the fabric of clothes.

Photonics is another field that's already incorporating graphene.

By integrating graphene into light-sensitive chips, cameras and other sensors can greatly improve sensitivity to even the faintest light waves across the visible and invisible spectrum.

That will not only improve the image quality of cameras and telescopes, but also medical imagery.

Filtration is yet another promising application of graphene.

Simple water purification filters built with graphene polymers can bind to organic and inorganic contaminants in drinking water.

Researchers at the Graphene Flagship have also created desalinization technologies based on graphene diodes that can remove over 60 percent of salt from seawater for agricultural and other uses.

All these developments will take time, but Ferrari at the Cambridge Graphene Centre is confident that graphene will live up to its hype.

In fact, he is equally excited about the yet-undiscovered properties of the estimated 2,000 other monolayer materials that are also being isolated, sticky tape method or otherwise.

"We say graphene, but we're really talking about a large number of options that are being explored," says Ferrari. "Things are moving in the right direction."

NOW THAT'S COOL

Sports equipment maker Head was one of the first to jump on the graphene bandwagon. Its Graphene XT tennis racket claims to be 20 percent lighter than racquets with the same swing weight.

Dave Roos

CONTRIBUTING WRITER

Dave is a freelance journalist who has contributed hundreds of articles to HowStuffWorks since 2007, with a specialty in personal finance, economics and business. Raised in Pittsburgh, Pennsylvania, he attended Duke University where he earned the B.A. in comparative religious studies that has served him so well.

Dave began freelancing when he and his wife moved to Mexico in 2003, publishing articles about Mexican food and culture in The New York Times, the Los Angeles Times and Newsweek. Nearly 15 years and three kids later, Dave and his family recently moved back to Mexico and just might stay a while.

https://science.howstuffworks.com/innovation/new-inventions/graphene.htm?utm_medium=push&utm_source=pushly&utm_campaign=640011

COAL – the Organic Rock - Coal is made up of organic components; specifically, plant matter that has been buried in an anoxic, or non-oxygenated, environment and compressed over millions of years. Because it is organic, coal defies the normal standards of classification for rocks, minerals, and fossils. Coal differs from every other kind of rock in that it is made of organic carbon: the actual remains, not just mineralized fossils, of dead plants. The carbon in coal was preserved from oxidation and remains in a chemically reduced form, available for oxidation.

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Coal

the organic rock

Everything You Need to Know About Coal

by Andrew Alden 

Coal is an enormously valuable fossil fuel that has been used for hundreds of years in industry.

It is made up of organic components; specifically, plant matter that has been buried in an anoxic, or non-oxygenated, environment and compressed over millions of years. 

Fossil, Mineral or Rock?

Because it is organic, coal defies the normal standards of classification for rocks, minerals, and fossils: 

·           A fossil is any evidence of life that has been preserved in rock. The plant remains that make up coal have been "pressure cooked" for millions of years. Therefore, it is not accurate to say that they have been preserved. 

·          Minerals are inorganic, naturally-occurring solids. While coal is a naturally-occurring solid, it is composed of organic plant material.

·          Rocks are, of course, made up of minerals. 

Talk to a geologist, though, and they'll tell you that coal is an organic sedimentary rock.

Even though it doesn't technically meet the criteria, it looks like a rock, feels like a rock and is found between sheets of (sedimentary) rock. So, in this case, it is a rock. 

Geology isn't like chemistry or physics with their steadfast and consistent rules. It is an Earth science; and like the Earth, geology is full of "exceptions to the rule." 

State legislators struggle with this topic as well: Utah and West Virginia list coal as their official state rock while Kentucky named coal its state mineral in 1998. 

Coal: the Organic Rock

Coal differs from every other kind of rock in that it is made of organic carbon: the actual remains, not just mineralized fossils, of dead plants.

Today, the vast majority of dead plant matter is consumed by fire and decay, returning its carbon to the atmosphere as the gas carbon dioxide.

In other words, it is oxidized. The carbon in coal, however, was preserved from oxidation and remains in a chemically reduced form, available for oxidation.

Coal geologists study their subject the same way that other geologists study other rocks.

But instead of talking about the minerals that make up the rock (because there are none, just bits of organic matter), coal geologists refer to the components of coal as macerals.

There are three groups of macerals: inertinite, liptinite, and vitrinite.

To oversimplify a complex subject, inertinite is generally derived from plant tissues, liptinite from pollen and resins, and vitrinite from humus or broken-down plant matter.

Where Coal Formed

The old saying in geology is that the present is the key to the past.

Today, we can find plant matter being preserved in anoxic places: peat bogs like those of Ireland or wetlands like the Everglades of Florida.

And sure enough, fossil leaves and wood are found in some coal beds.

Therefore, geologists have long assumed that coal is a form of peat created by the heat and pressure of deep burial.

The geologic process of turning peat into coal is called "coalification."

Coal beds are much, much larger than peat bogs, some of them tens of meters in thickness, and they occur all over the world.

This says that the ancient world must have had enormous and long-lived anoxic wetlands when the coal was being made. 

Geologic History of Coal

While coal has been reported in rocks as old as Proterozoic (possibly 2 billion years) and as young as Pliocene (2 million years old), the great majority of the world's coal was laid down during the Carboniferous Period, a 60-million-year stretch (359-299 m.y.a.) when sea level was high and forests of tall ferns and cycads grew in gigantic tropical swamps.

The key to preserving the forests' dead matter was burying it.

We can tell what happened from the rocks that enclose the coal beds: there are limestones and shales on top, laid down in shallow seas, and sandstones beneath laid down by river deltas.

Obviously, the coal swamps were flooded by advances of the sea. This allowed shale and limestone to be deposited on top of them.

The fossils in the shale and limestone change from shallow-water organisms to deep-water species, then back to shallow forms.

Then sandstones appear as river deltas advance into the shallow seas and another coal bed is laid down on top. This cycle of rock types is called a cyclothem.

Hundreds of cyclothems occur in the rock sequence of the Carboniferous. Only one cause can do that - a long series of ice ages raising and lowering the sea level.

And sure enough, in the region that was at the south pole during that time, the rock record shows abundant evidence of glaciers.

That set of circumstances has never recurred, and the coals of the Carboniferous (and the following Permian Period) are the undisputed champions of their type.

It has been argued that about 300 million years ago, some fungus species evolved the ability to digest wood, and that was the end of the great age of coal, although younger coal beds do exist.

A genome study in Science gave that theory more support in 2012. If the wood was immune to rot before 300 million years ago, then perhaps anoxic conditions were not always necessary.

Grades of Coal

Coal comes in three main types or grades. First, the swampy peat is squeezed and heated to form a brown, soft coal called lignite.

In the process, the material releases hydrocarbons, which migrate away and eventually become petroleum.

With more heat and pressure lignite releases more hydrocarbons and becomes the higher-grade bituminous coal.

Bituminous coal is black, hard and usually dull to glossy in appearance.

Still greater heat and pressure yields anthracite, the highest grade of coal. In the process, the coal releases methane or natural gas.

Anthracite, a shiny, hard black stone, is nearly pure carbon and burns with great heat and little smoke. 

If coal is subjected to still more heat and pressure, it becomes a metamorphic rock as the macerals finally crystallize into a true mineral, graphite.

This slippery mineral still burns, but it is much more useful as a lubricant, an ingredient in pencils and other roles.

Still more valuable is the fate of deeply buried carbon, which at conditions found in the mantle is transformed into a new crystalline form: diamond.

However, coal probably oxidizes long before it can get into the mantle, so only Superman could perform that trick.

Andrew Alden

Professional geologist, writer, photographer, and geological tour guide

Thirty-seven years of experience writing about geological subjects

Six years as a research guide with U.S. Geological Survey (USGS)

Member of Geological Society of America (GSA), and American Geophysical Union (AGU)

Experience

Andrew Alden is a former writer for ThoughtCo who contributed hundreds of articles for more than 17 years. Andrew works as a geologist, writer, editor, and photographer. He has written on geological subjects since 1981 and participates actively in his field. For example, Andrew spent six years as a research guide with the U.S. Geological Survey, leading excursions on both land land and at sea. And since 1992, he has hosted the earthquakes conference for the online discussion platform, The Well, which began as a dialogue between the writers and readers of the Whole Earth Review. 

In addition, Andrew is a longtime member of the member of the Geological Society of America — an international society that serves members in academia, government, and industry; and the American Geophysical Union — a community of earth and space scientists that advances the power of science to ensure a sustainable future.

Andrew lives in Oakland, California; and though he writes about the whole planet and beyond, Andrew finds his own city full of interest too and blogs about its geology. 

Education

Andrew Alden holds a bachelor's (B.A.) degree in Earth Science from the University of New Hampshire, College of Engineering and Physical Sciences, in Durham, N.H.

Awards and Publications

Andrew Alden on Earthquakes ​(The Well Group, Inc., 2011)

Assessment of River — Floodplain Aquifer Interactions (Environmental and Engineering Geoscience, 1997)

Andrew Alden on Hosting (The Well Group, Inc., 1995)

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https://www.thoughtco.com/all-about-coal-1440944