"Show your work" and "Explain"

In every field and for every instructor, there are certain instructions and questions that may not be explicitly stated, but are always implied. The two that I see people having the most consistent problems with are:
1. "Show your work" - If you are doing a calculation, you must ALWAYS show your work. If a question asks you to calculate the concentration of a solution, the answer is never just "1.18M". Show how you got to that number. You're doing it anyway, you should show it. If you're not doing it, then you're either "borrowing" an answer from someone else or guessing. Show your work. Sometimes, the way the question is worded might make it seem like you don't have to show your work ("What is the concentration of solution A?"), but you still need to show your work. The only real exception to "show your work" is for exceptionally trivial calculation, like adding up a molar mass (although you still should include the correctly balanced formula for anything you're adding up a molar mass for) or taking an average (if you really want to show the steps in taking an average, that's OK, but "average" is a standard enough operation that I don't require you to show your work). How do you decide if something is trivial or common enough that you don't have to show your work? One quick way to check is if the units have to be changed or transformed during the calculation. If the units change, show your work. When in doubt, show your work. If you're not sure, show your work. Even if you're really brilliant, show your work.
1a. "Show your work" = "Show your units" - This is another one that should be implied... In chemistry, there are a couple quantities that are unitless (pH, equilibrium constants), but the VAST majority of numbers should include units. If you do not show your units, you have not shown your work. Always show units on every number that has them. THE ONLY EXCEPTION is in tabulated data where the units can (and often should) be included in the column heading of the table rather than on each individual number.
2. "Explain" - If science was only used to answer the "what" aspects of our daily lives, it would be pretty boring. Science answers the "what" AND the "why". The "why" is always implied. This is the text analog of "show your work". I do not tend to ask questions that I feel can be answered in 1 word or a short phrase. I want to see an explanation of why the answer you gave makes sense in relation to the data you have collected. This does not mean that you have to write a page and a half to answer every question, but it does mean that a sentence or two (or more) is probably required. Support your answers with meaningful data or other explanations, it makes for a much clearer answer.