Acyclic hydrocarbon cyclopentane has five carbons and is a ring-shaped molecule. It is a member of the family of cycloalkanes. Cyclopentane is used to make rubber glue, synthetic rubber, and resins. When making polyurethane, cyclopentane foam is also used as a blowing agent. They are also used in the manufacture of fuels as a solvent. Its look is colourless, and its odour is similar to that of fuel.