Leg press, deadlifts, RDLs, lunges, leg extensions, leg curls, hack squats, split squats. All those will hit your legs, plus there variations. Do some sprints, run hills, stairs, those will hit your legs. Im sure there are more lifts I can't think of this second as well.
While natural gas occurs in nature as a mixture of methane and other gases, propane is actually a byproduct of both petroleum refining and natural gas processing.
Oil is a liquid, but propane is a gas. Liquids are fluid, like water, but gases seem to have no visible appearance, like air. Gas is a general term for air-like substances, but there are specific gases that can be ignited and used for heating. You can choose between natural gas and propane for your home heating system.