A molecular substance is a substance made up of a large collection of individual molecules, each consisting of atoms held together by covalent bonds. Such substances often have relatively low melting and boiling points because only weak forces act between the separate molecules. Water and carbon dioxide are molecular substances, in contrast to ionic substances such as sodium chloride.

分子物质是由大量独立分子聚集而成的物质,每个分子由共价键结合的原子构成。这类物质的熔点和沸点通常较低,因为分子之间只存在较弱的作用力。水和二氧化碳是分子物质;与之相对的是氯化钠等离子化合物。