How do the properties of graphite influence its use in pencils?

Graphite's properties of being soft, slippery and leaving a mark on paper make it ideal for use in pencils.

Graphite, a form of carbon, is used in pencils due to its unique physical properties. It is soft and slippery, which allows it to easily slide across paper and leave a mark. This is due to the structure of graphite, which consists of layers of carbon atoms arranged in a hexagonal lattice. These layers are weakly bonded together, allowing them to slide over each other easily. This is why when you write with a pencil, the graphite layers slide off and stick to the paper, leaving a visible mark.

Another important property of graphite is its hardness, which can be adjusted by adding different amounts of clay. The more clay added, the harder the pencil lead becomes. This allows for the production of pencils with different hardness levels, suitable for different writing and drawing needs. For example, a 2B pencil has less clay and more graphite, making it softer and darker, while a 2H pencil has more clay, making it harder and lighter.

Furthermore, graphite is chemically inert, meaning it does not react with other substances easily. This makes it safe to use, as it won't react with the paper or the user's skin. It is also resistant to moisture, so it won't be affected by humidity or sweat from the user's hand.

Lastly, graphite is abundant and easy to mine, making it a cost-effective choice for pencil manufacturing. It can be found in large quantities in countries like China, India and Brazil, and can be easily extracted and processed.

In summary, the properties of graphite, including its softness, slipperiness, adjustable hardness, chemical inertness and abundance, make it the perfect material for use in pencils.