A catalyst is a compound which allows a chemical reaction to occur without undergoing a chemical change itself. Thus it is not 'used up' when performing its function. Thus the word catalyst is a common metaphor for something which is not expended when used.
Is there a word to mean the opposite? For example food and firewood can only be used once. In usage they are, by definition, expended. They are examples of _______.
This is in contrast with, say, a nappy, which is still a nappy after being soiled. However a clean nappy might be an example of a _______ as after used it is no longer a clean nappy.
I would love if _____ were also a piece of chemistry jargon which passed into lay usage.