Yes, many mass nouns have a corresponding count noun with a slightly different meaning. A [type of] sugar, a [glass of] water. I was trying to think of example

Yes, many mass nouns have a corresponding count noun with a slightly different meaning. A [type of] sugar, a [glass of] water. I was trying to think of example where this can't be done, but even "a [molecule of] dextrose" is something I could imagine a chemist saying.