If enough heating occurs, the mass of air becomes warmer and lighter than the air in the surrounding environment, and just like a hot air balloon it begins to rise, expand, and cool.
(enough heating; occurs; ) (it; to expand; ) (the mass of air; becomes; warmer and lighter than the air in the surrounding environment) (it; begins; ) (it; to rise; )
enough heating it the mass of air it it
occurs to expand becomes begins to rise
warmer and lighter than the air in the surrounding environment