What really happens is that the fire heats the air in the bottle, which in turn causes it to expand and rise.
(it; to rise; ) (What really happens; is; that the fire heats the air in the bottle) Context(What really happens is,List([0, 22))):(the fire; heats; the air; L:in the bottle) (the bottle; causes; it to expand and rise) Context(the bottle causes,List([54, 86))):(it; to expand; )
What really happens is,List([0, 22)) the bottle causes,List([54, 86))
it What really happens the fire the bottle it
to rise is heats causes to expand
that the fire heats the air in the bottle
the air L:in the bottle
it to expand and rise