How does the viscosity of a hydrocarbon change as its size increases?

The viscosity of a hydrocarbon increases as its size increases due to the larger molecules having more surface area and a greater number of intermolecular forces acting between them. As the size of the hydrocarbon chain gets longer, the chains can become entangled and experience greater resistance to flow because the interactions between the molecules become stronger. This increased intermolecular attraction causes the liquid to flow less readily, resulting in a higher viscosity.

In smaller hydrocarbons, the molecules are less complex and have fewer interactions, making them less viscous and allowing them to flow more easily. As the hydrocarbon becomes larger and its molecular weight increases, the increased complexity and interactions lead to a rise in viscosity. This characteristic relationship between size and viscosity is important in various applications, such as fuel production and lubricant formulation, where the flow properties of these substances are essential.