When the substances `Si, KCl, CH_(3)OH and C_(2)H_(6)` are arranged in order of increasing melting point, what is the correct order ?

Options

A. `Si, KCl, CH_(3)OH, C_(2)H_(6)`
B. `CH_(3)OH,C_(2)H_(6),Si,KCl`
C. `KCl,Si,C_(2)H_(6),CH_(3)OH`
D. `C_(2)H_(6),CH_(3)OH,KCl,Si`

Explanation

To determine the order of increasing melting points for the substances Si, KCl, CH₃OH, and C₂H₆, we need to analyze the type of bonding and structure present in each substance.

### Step-by-Step Solution:

1. **Identify the substances and their bonding types:**
- **Si (Silicon):** Silicon is a covalent network solid. It has a giant covalent structure, meaning that it consists of a large number of atoms bonded together by strong covalent bonds.
- **KCl (Potassium Chloride):** KCl is an ionic compound. It forms a lattice structure where K⁺ and Cl⁻ ions are held together by strong electrostatic forces.
- **CH₃OH (Methanol):** Methanol is a molecular compound. It has covalent bonds within the molecule, but the intermolecular forces are primarily hydrogen bonds, which are weaker than ionic or covalent bonds.
- **C₂H₆ (Ethane):** Ethane is also a molecular compound, but it is non-polar and has very weak London dispersion forces as its intermolecular forces.

2. **Determine the melting points based on bonding:**
- **Silicon (Si):** High melting point due to strong covalent bonds in its network structure. Approximate melting point: 1414 °C.
- **KCl:** High melting point due to strong ionic bonds in its lattice structure. Approximate melting point: 770 °C.
- **CH₃OH:** Lower melting point due to hydrogen bonding, which is weaker than ionic and covalent bonds. Approximate melting point: -97.6 °C.
- **C₂H₆:** Lowest melting point due to weak London dispersion forces. Approximate melting point: -182.8 °C.

3. **Arrange the substances in order of increasing melting point:**
- Start with the lowest melting point: C₂H₆ (-182.8 °C)
- Next is CH₃OH (-97.6 °C)
- Then KCl (770 °C)
- Finally, Si (1414 °C)

4. **Final order of increasing melting points:**
- C₂H₆ < CH₃OH < KCl < Si

### Conclusion:
The correct order of increasing melting points for the substances Si, KCl, CH₃OH, and C₂H₆ is:
C₂H₆ < CH₃OH < KCl < Si