Final answer:
Methane does not dissolve in water due to its nonpolar molecular structure which repels the polar water molecules. Water’s polarity allows it to dissolve polar or ionic substances, but nonpolar molecules like methane do not interact favorably with water, hindering their solubility.
Step-by-step explanation:
Methane does not dissolve in water because water is polar and methane is a nonpolar molecule. Substances that are polar or ionic tend to dissolve in water due to their ability to form hydrogen bonds with water molecules or dissociate into ions. Methane lacks those polar groups that are vital for solubility in water and instead has a nonpolar molecular structure that repels water molecules, which is why methane is not miscible with water. Compounds such as methanol, on the other hand, are polar and can form hydrogen bonds with water due to the presence of polar OH groups. In general, the larger the nonpolar portion of a molecule, the less soluble it becomes in water as it increasingly repels the polar nature of water.
Henry's law further explains that gases that do not chemically react with water, like methane, are less soluble. In contrast, gases that react with water, such as hydrogen chloride (HCl), form aqueous ions which makes them very soluble in water. The universality of water as a solvent is linked to its ability to dissolve many substances, a characteristic not shared with methane due to its nonpolar structure.