Is Carbon Solid, Liquid or Gas? (+ 3 Things to Know)

At standard temperature and pressure (STP), carbon exists as a solid, which is commonly known as graphite. ¹ However, at very high temperatures and pressures, carbon can exist in a liquid or gaseous state, such as in the form of molten lava or carbon dioxide gas. ²

Well, this was just a simple answer. But there are few more things to know about this topic which will make your concept super clear.

So let’s dive right into it.

Why does carbon exist as a solid at room temperature?

Carbon exists as a solid at room temperature due to its unique atomic structure and bonding properties. At room temperature and normal atmospheric pressure, carbon atoms bond together in a crystalline structure known as graphite, which consists of layered sheets of hexagonal rings. ³

Each carbon atom in graphite is bonded to three neighboring carbon atoms through strong covalent bonds, resulting in a very stable and strong structure. ⁴ These strong bonds require a significant amount of energy to break apart, which is why carbon does not easily transition from a solid to a liquid or gas at room temperature.

Another form of carbon is diamond, which is also a solid at room temperature. Diamond is even harder and more durable than graphite due to its unique tetrahedral bonding structure, in which each carbon atom is bonded to four neighboring carbon atoms. This type of bonding results in a dense, three-dimensional network of atoms that is even more stable than graphite. ^{5 6 7}

In summary, carbon exists as a solid at room temperature due to its strong covalent bonding properties and the unique atomic structures of its two most common forms: graphite and diamond.

Does carbon exist in a liquid state?

Yes, carbon can exist in a liquid state, but it requires very high temperatures and pressures. ⁸

One example of liquid carbon is in the form of molten iron-carbon alloys, which are used in the production of steel. ⁹ In this process, carbon is added to iron at high temperatures, resulting in a liquid mixture of iron and carbon. However, the amount of carbon in these alloys is typically less than 6.67% by weight, and the melting point is still quite high, typically around 1150-1300°C. ^{10 11}

Another example is liquid carbon dioxide (CO₂), which is a common industrial and laboratory solvent. At standard atmospheric pressure, liquid carbon dioxide has a boiling point of -78.5°C and a melting point of -56.6°C. ^{12 13} However, in order to achieve a liquid state, carbon dioxide must be kept under high pressure, typically over 5.1 atm. ¹⁴

In general, carbon is not commonly found in a liquid state under normal conditions, and it usually requires extreme temperatures and/or pressures to achieve a liquid phase.

How is solid carbon different from liquid carbon?

Solid carbon and liquid carbon are different in terms of their physical state and molecular arrangement.

Solid carbon

Solid carbon exists in two common forms: diamond and graphite. ¹⁵

Diamond consists of a three-dimensional network of carbon atoms arranged in a tetrahedral structure, while graphite consists of layers of carbon atoms arranged in a hexagonal lattice.

In both forms, the carbon atoms are held together by strong covalent bonds, resulting in a solid material with a high melting point and a rigid structure.

Liquid carbon

Liquid carbon, on the other hand, can exist in several forms depending on the conditions under which it is formed.

For example, molten iron-carbon alloys are a type of liquid carbon in which carbon is mixed with iron at high temperatures.

Liquid carbon can also exist in the form of liquid carbon dioxide (CO2), which is a common industrial and laboratory solvent. In liquid form, carbon atoms are not held together by rigid covalent bonds, but rather are free to move around and interact with other atoms, resulting in a fluid material with a lower melting point and a less rigid structure. ¹⁶

In summary, solid carbon and liquid carbon differ in terms of their physical state, molecular arrangement, and properties such as melting point, rigidity, and fluidity.

Further reading

Is Boron a Solid, Liquid or Gas?
Is Hydrogen a Solid, Liquid or Gas?
Is Mercury Solid, Liquid or Gas?
Is Phosphorus a Solid, Liquid or Gas?
Is Sodium a Solid, Liquid or Gas? 

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