Carbon – Properties and Applications

Chemical Formula

C

Topics Covered

Background

Since prehistoric days, humans have been aware of the presence of carbon. When the cave people made a fire, they saw the formation of smoke. The black smoke color is indicatives of carbon particles from unburned materials.

Later, oil was used as a fuel for lamps. The burning of oil resulted in the release of carbon, which formed a sooty covering on the lamp interior. This sooty covering came to be known as lampblack. Lampblack was mixed with balsam gum or olive oil to make ink.

Charcoal is the most common form of carbon. Wood when heated in the absence of air, in particular oxygen, results in the formation of charcoal. The French Physicist René Antoine Ferchault Reaumur, realized that carbon may be an element and published work to this effect in 1722. The official classification of carbon happened during the end of the 18th century. It was initially named Carbone based on the previous Latin term for charcoal, charbon.

There are almost ten million carbon compounds and ‘organic chemistry’ is a branch of chemistry that deals with the study of these carbon compounds. The following are some common carbon compounds:

• Acetic acid (CH₃COOH)
• Ethyl alcohol (C₂H₅OH)
• Acetylene (C₂H₂)
• Benzene (C₆H₆)
• Methane (CH₄)
• Ethylene (C₂H₄)
• Carbon tetrachloride (CCl₄)
• Chloroform (CHCl₃)
• Carbon dioxide (CO₂)
• Carbon monoxide (CO)
• Carbon disulfide (CS₂)

Basic Information of Carbon

Table 1. Basic Properties of Carbon

Occurrence of Carbon

Almost 18% of an individual’s body weight is due to carbon. Carbon is the second most common element in the human body, the fourth most common element in the solar system, the sixth most common element in the universe and the 17^th most common element in the Earth’s crust. Carbon occurs in minerals such as magnesium (MgCO₃) and calcium carbonate (CaCO₃) and rarely occurs as graphite and diamond. Carbon also occurs in the form of carbon dioxide (CO₂) present in the atmosphere. Though carbon dioxide makes up only a small part of the atmosphere, it is a very crucial gas as it is used for photosynthesis. A few varieties of coal are almost pure carbon. Natural gas, coal and oil have carbon in them. Natural gas and oil are all hydrocarbons that are compounds made from hydrogen and carbon.

Carbon and Nanotechnology

While allotropes of carbon such as graphite and diamond have been known for centuries other allotropes such as carbon nanotubes, graphene and buckminsterfullerene have been discovered more recently. These have played significant roles in the development of the field of nanotechnology.

In basic terms they can be described as:

• Graphene – A single sheet of carbon atoms arranged in a hexagon pattern, such that all carbon atoms are bonded to 3 other carbon atoms
• Carbon Nanotubes– A tube made from a graphene sheet (single-walled carbon nanotubes). Variations include tubes closed at one or both ends, and tubes made by rolling graphene sheets such that they are several layers thick (multi-walled carbon nanotubes).
• Buckminsterfullerene– Sometimes called buckyballs, they normally consist of 60 carbon atoms bonded together to form a spherical structure with 20 hexagonal faces and 12 pentagonal faces.

Isotopes

Carbon-12, carbon-13, and carbon-14 are the three isotopes of carbon that occur naturally.

Carbon-14 is radioactive and is used to measure the thickness of objects e.g. steel sheets. It is also used in “carbon dating” of archaeological samples where scientists use the half life of the carbon-14 to determine the age of samples.

Production of Carbon

Graphite, diamond and other carbon forms are directly obtained from mines. Synthetic diamonds can be produced when pure carbon is subjected to extremely high temperatures and pressures. Today, about 1/3^rd of all diamonds are synthetically produced.

Health Aspects of Carbon

Carbon is absolutely essential for life and almost every molecule in a living organism contains carbon. Carbon also has a few ill effects on living organisms. Black lung, for instance is a disease developed in coal miners. The miner’s lung develops a black color that is caused when coal dust is inhaled by the miner. This coal dust blocks the small holes through which oxygen enters the lungs resulting in breathing difficulty, that can in the worst instance result in death.

Key Properties of Carbon

• Carbon burns in air to form carbon monoxide and carbon dioxide.
• Carbon reacts with oxygen but does not react or dissolve in acids, water and other such materials.
• Carbon has the ability to develop long chains, which are virtually endless. For instance, plastic molecules have a long chain of carbon atoms linked to each other and some of them also have side-chains.
• Carbon is present in many allotropic forms. Graphite and diamond are allotropes that possess crystalline structures. Allotropes without crystalline structures are either without a shape or amorphous.
• Coke, charcoal, carbon allotropes and lampblack are non-crystalline allotropes.

Applications of Carbon

Graphite and diamonds are two important allotropes of carbon that have wide applications.

Diamonds are expensive and attractive and hence used in high end jewellery. Industrial diamonds are used to cut, polish and grind glass because of their extreme hardness.

Graphite used in:

• Nuclear power plants to help slow down the neutrons in a nuclear reaction
• Graphite used in lead pencils
• Graphite is used as a lubricant for machines and mechanical parts
• Graphite refractories are used when non-wetting furnace linings are required and oxidation is not an issue e.g. in aluminium production and in vacuum furnaces

Amorphous carbon also finds a variety of applications such as in:

• Rubber tires
• Inks
• Pigments
• Phonograph records
• Stove polish
• Typewriter ribbons.

Source: AZoM.com