The context establishes the fundamental principle that 'polar solutes dissolve in polar solvents and non-polar solutes in non-polar solvents' - commonly expressed as 'like dissolves like.' Water is a polar solvent. Formic acid and ethylene glycol are highly soluble because they are polar compounds with strong hydrogen bonding capability with water molecules. Phenol and pentanol are partially soluble because they contain polar -OH groups but also have non-polar hydrocarbon portions that reduce their overall solubility. Toluene and chloroform are insoluble because they are predominantly non-polar compounds that cannot form favorable interactions with polar water molecules.