Why do diamond and graphite, the two allotropic forms of carbon evolve different amounts of heats on combustion?

Explanation

### Step-by-Step Solution:

1. **Understanding Allotropes**:
- Allotropes are different forms of the same element that exist in the same physical state but have different structures and properties. In this case, carbon exists in two allotropic forms: diamond and graphite.

2. **Structure of Diamond and Graphite**:
- Diamond has a tetrahedral structure where each carbon atom is bonded to four other carbon atoms in a three-dimensional network. This structure is very rigid and strong.
- Graphite, on the other hand, has a planar structure where each carbon atom is bonded to three other carbon atoms, forming layers of hexagonal rings. These layers can slide over each other, making graphite softer and more lubricating.
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