Allotropy and Allotropes of Carbon - Crystalline Allotropes of Carbon: Graphite

Graphite is a naturally occurring form of carbon found in countries like Russia, New Zealand, America, and India. It is widely used in pencils, where it is mixed with clay, a process discovered by Nicholas Jacques Conte in 1795. Graphite has a unique structure where carbon atoms are bonded in hexagonal layers, allowing the layers to slide over one another, making it versatile and useful in various applications.

Graphite and structure of carbon atoms in graphite

• Graphite is black, soft, brittle, and has a slippery texture, making it distinct from other forms of carbon.
• It is a good conductor of electricity because free electrons move within each layer of its structure.
• The layered structure enables its use in writing, as layers easily slip off onto paper.
• The density of graphite ranges from 1.9 to 2.3 g/cm³, depending on its form.
• Graphite is highly resistant to most solvents, maintaining its stability in various environments.
• Its structure consists of multiple layers of carbon atoms; one individual layer is referred to as graphene.
• The ability of layers to slide over each other makes graphite an excellent lubricant in industrial applications.

1. Aim: To study the physical and electrical properties of pencil lead (graphite) and its behaviour in different liquids.

2. Requirements: pencil lead, electrical wires, battery/cell, small bulb, water, kerosene, test tubes, and lead dust.

3. Procedure

• Remove the lead from a pencil, feel its texture and colour, and check its brittleness by attempting to break it.
• Assemble the electrical circuit using the pencil lead as shown in the diagram and switch on the current. Observe whether the bulb glows.
• Add lead dust to water in one test tube and kerosene in another. Observe its behaviour in both liquids.

Flow of electric current through graphite

4. Conclusion: Pencil lead (graphite) is brittle, black, and soft. Graphite conducts electricity, as indicated by the glowing bulb in the circuit. Lead dust does not dissolve in water or kerosene, showing its insolubility in common solvents.

1. Graphite is used to make lubricants due to its slippery and layered structure.
2. It is used in the production of carbon electrodes because it conducts electricity.
3. Graphite is commonly used in pencils for writing, as it easily leaves marks on paper.
4. It is an essential ingredient in paints and polishes for adding smoothness and durability.
5. Graphite is utilised in arc lamps, which produce very bright light, making them useful in film and photography.
6. It is used as a moderator in nuclear reactors due to its ability to slow down neutrons.
7. Graphite is applied in industrial moulds and foundries because it can withstand high temperatures.
8. It is used in batteries as an electrode material, especially in lithium-ion batteries.
9. Graphite is used in brake linings and gaskets for its durability and thermal resistance.