What effect does branching of an alkane chain have on its melting point?A.Increase its melting pointB.Decreases its melting pointC.Doesn’t change its melting pointD.Cannot be determined

The effect of branching in alkane chains on their melting points is an important concept in organic chemistry. Here's the explanation:

### Explanation:

1. **Structure of Alkanes**:
- Alkanes are saturated hydrocarbons with the general formula \( C_nH_{2n+2} \). They can have straight-chain (linear) or branched structures.

2. **Melting Point of Alkanes**:
- The melting point of a substance is influenced by the forces between its molecules. For alkanes, these forces are primarily van der Waals (dispersion) forces.
- In a straight-chain alkane, the molecules can pack closely together, allowing for stronger intermolecular forces and thus a higher melting point.
- In contrast, branched alkanes have a more compact and less linear shape, which disrupts close packing.

3. **Effect of Branching**:
- **Increased Branching**: When the alkane chain is branched, it becomes bulkier and less symmetrical. This reduces the surface area available for intermolecular interactions, leading to weaker van der Waals forces.
- As a result, branched alkanes typically have lower melting points compared to their straight-chain isomers.

### Conclusion:
Therefore, the branching of an alkane chain **decreases its melting point**.

The correct answer is **B. Decreases its melting point**.