Question

in every energy transformation, some energy is always lost as what energy

Answer 1

can't really say the exact form. cause it depends on the system and its workings. but this figure comes up when we are dealing with the classical level physics, we can use the word "lost" here but at atomic and sub atomic level we can observe energy transformations without missing it.

Answer 2

Yes, in day-to-day situations, the energy is typically lost as heat. "Every" is a worrisome word, as is "always."