heart and soul vs kernel

heart and soul and kernel both are nouns.

Word	Noun	Adjective	Verb	Adverb
heart and soul	Yes	No	No	Yes
kernel	Yes	No	No	No

As nouns, heart and soul and kernel are synonyms defined as:

heart and soul and kernel: the choicest or most essential or most vital part of some idea or experience

Other synonyms of heart and soul include center, centre, core, essence, gist, heart, inwardness, marrow, meat, nitty-gritty, nub, pith, substance, sum.

heart and soul (noun)	kernel (noun)
the choicest or most essential or most vital part of some idea or experience	the choicest or most essential or most vital part of some idea or experience
	a single whole grain of a cereal
	the inner and usually edible part of a seed or grain or nut or fruit stone

heart and soul (adverb)	kernel (adverb)
with complete faith