Question

Is methanol soluble in water?

Answer 1

The relative strength of the hydrophobic and hydrophilic interactions present in a covalent molecule determine its solubility. When the hydrophobic interactions dominate then the molecule becomes insoluble and when the hydrophilic interactions dominate the molecule becomes soluble in water.

Complete answer:
Most compounds follow the solubility principle of dissolves like i.e. only those compounds are soluble in a particular solvent that have the same nature of bonds as that present in the solvent. Therefore it is observed that organic compounds generally get dissolved in organic solvents like cyclohexane and benzene. Mineral acids, alkalis and ionic salts tend to get dissolved in inorganic solvents like water and ammonia due to their polar nature and the ability to stabilize the ions formed by the dissociation of ionic compounds.
The enthalpy of solvation and nature of interaction between the molecules of solute with itself and that of the solvent are the two important factors that decide the solubility of a substance.
Water as a solvent dissolves a large number of compounds and is therefore known as the universal solvent. Covalent compounds like hydrocarbons with polar functional groups tend to have two types of interaction with water. The oxygen containing polar group known as hydrophilic group is capable of forming hydrogen bonds with water that enhances its solubility in it. The alkyl chain is the hydrophobic part of the molecule that resists interactions with water and decreases the solubility.
Therefore if the alkyl chain is long enough for the hydrophobic part to dominate then the compound is insoluble. But if the alkyl chain is short and the functional group is hydrophilic enough then the compound becomes soluble.
Since methanol $(C{H_3}OH)$ is the shortest member of the alcohol family with only one carbon atom, the hydrophobic interactions are weak and sufficient hydrogen bonds are formed to make it soluble in water.
Thus, methanol is soluble in water.

Note:
The solubility of compounds is not just dependent upon the interactions involved in between the solute and solvent molecules but also on many other physical factors such as temperature. Heating a mixture can enhance or lower the extent of dissolution of a compound in a particular solvent.