Thank you, ChrisHunt.
There is an important distinction between things that are "how many" and things that are "how much," as CajunCenturion alluded to.
Sand, water, air, gum, and the like are collection words for which one must ask "how much." They generally require not just a value but a unit: 1 pound of sand, 1 liter of water, 1 cubic meter of air, 1 pound of gum. Some can be used with "how many" by some alteration. How many grains of sand, molecules of water or air, sticks of gum?
Yes, there are some things which can be viewed in both ways: we order "a water" and mean a glass of water, a bottle of water. With enough time and common usage, it may one day be correct to say "a gum." But in the meantime, I think it is "some gum" or "a stick of gum."
As for piece of paper... I've never heard of that referring only to a torn piece. Whenever I ask someone for a piece of paper, they know I want a whole one.
One of these how many/how much confusions that I remember is with "corn." I worked at the fair as a teenager and was galled to hear people ordering "two corns" instead of "two cobs of corn." It took a heroic effort to say nothing about
calluses on feet!
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It is better to have honor than a good reputation.
(Reputation is what other people think about you. Honor is what you know about yourself.)