Heat makes it expand, it becomes less dense than the surrounding air and buoyant, and it rises like a hot-air balloon (or like a drop of oil in a bottle of water).
(it; rises; ) (it; becomes; less dense than the surrounding air and buoyant) Context(it becomes,List([22, 32))):(Heat; makes; it expand) Context(Heat makes it becomes,List([0, 32))):(it; expand; )
it becomes,List([22, 32)) Heat makes it becomes,List([0, 32))
it it Heat it
rises becomes makes expand
less dense than the surrounding air and buoyant
it expand