Final answer:
Both CH₄ and H₂ are nonpolar and typically have low solubility in water. However, due to its small size, H₂ may have a very slight edge in solubility in water compared to CH₄, but neither are significantly soluble.
Step-by-step explanation:
The question is asking which substance, CH₄ (methane) or H₂ (hydrogen), is expected to be most soluble in water. Water is a polar solvent, and solute solubility often depends on the 'like dissolves like' principle where polar solutes are more soluble in polar solvents, and nonpolar solutes are more soluble in nonpolar solvents. Methane is a nonpolar molecule, and hydrogen is a nonpolar diatomic molecule; however, hydrogen has a special case due to its very small size and ability to engage in some interactions with water.
However, methane is a hydrocarbon with weak Vander Waals forces and low polarity, making it essentially insoluble in water. Hydrogen, being a nonpolar molecule, would not typically be soluble in water. But due to its small size and special status as a gas at room temperature, it can have minimal solubility in water due to its ability to occupy spaces between water molecules. Nonetheless, neither of these molecules are particularly soluble in water, but considering the options, H₂ may have a very slight edge over CH₄ in terms of solubility in water.