Question

When diamond is strongly heated to \(2000^{\circ} \mathrm{C}\) in vacuum, we get (1) amorphous carbon (2) charcoal (3) graphite (4) fullerene

Short answer

Graphite

Step-by-step solution

Understanding the Context

Identify what diamond is: a solid form of carbon with a crystal structure. When heated, its form can change.

Properties of Diamond

Recall that diamond turns into a different form of carbon when subjected to very high temperatures.

Effect of Heating on Diamond

Note that strong heating of diamond in a vacuum (no oxygen present) will cause it to change structure.

Expected Result at 2000°C

Determine that at such high temperatures, in a vacuum, the stable form of carbon is graphite.

Verify the Answer

Cross-check with the provided options to find that graphite is listed.

Key concepts

carbon allotropes

Carbon exhibits different forms, known as allotropes. These allotropes display varied properties due to differences in the arrangement of carbon atoms. The most well-known carbon allotropes include:

• Diamond – characterized by a crystal structure that makes it extremely hard and transparent.
• Graphite – comprises layers of carbon atoms that slide over each other, making it slippery and an excellent conductor of electricity.
• Fullerene – molecules composed entirely of carbon, forming a hollow sphere or tube.
• Amorphous Carbon – lacks a clear structure, often appearing in materials like coal and charcoal.

These differences arise from the way carbon atoms bond with one another in each form, impacting properties like hardness, electrical conductivity, and thermal stability.

crystal structure

The crystal structure defines how atoms are arranged in a solid. In the case of diamond, each carbon atom forms four strong covalent bonds in a tetrahedral structure. This arrangement is responsible for its renowned hardness and transparency.
Here are some key facts about the crystal structure of diamond:

• Tetrahedral bonding – each carbon atom is covalently bonded to four other carbon atoms.
• High symmetry – diamond has a cubic crystal system.
• Strong bonds – the covalent bonds make diamond extremely hard and durable.

When diamond transforms into graphite, the crystal structure changes significantly. Graphite’s carbon atoms are arranged in layers, with each atom bonded to three others in a triangular lattice. This creates sheets that can slide over one another, giving graphite its slippery feel and conductivity.

thermal transformation

Thermal transformation involves changing the form of a material by heating it. When diamond is heated to around 2000°C in vacuum, it undergoes a thermal transformation.
Here are the steps involved:

• Initial Heating – diamond’s crystal structure begins to break down as the temperature rises.
• Transition Phase – at around 2000°C, in the absence of oxygen (vacuum), diamond transforms into graphite.
• Stabilization – the new arrangement of carbon atoms in graphite becomes stable under these conditions.

It’s important to note that heating in vacuum prevents oxidation, which would otherwise create different forms of carbon. This thermal transformation is a fascinating example of how altering conditions like temperature and pressure can lead to significant material changes.