Adhesives and sealants perform two different functions, though some of the properties are common. Adhesives are used to bind two materials together and prevent them from separating. Sealants are used to block gases and liquids from entering the surface on which it has been applied. Depending on the type of sealant, they have multiple functions; they keep out moisture, provide insulation, and protect against fire. Some sealants may have adhesive properties, and some adhesives may have sealing qualities. However, sealants are generally more elastic to stretch over a surface and have less strength than adhesives which must hold together two surfaces.