And the answer is...
1. Every natural element has some impact on me, though some more than others.
2. I am not changed in any way by a temperature increase.
What am I?
Seawater salinity! (and for this question, I'm defining that as including all nonwater components of seawater; see below)
Mass is almost a correct answer. Mass of seawater or mass of a reef tank would be a correct answer, because every element is present and adds to the mass of almost any reasonable amount of seawater. Mass is also not impacted by temperature. But "mass" alone without some qualifier of what mass we are talking about does not fit clue 1. Mass of the air in your home, for example, would not be impacted by all natural elements. thus, I would not give credit for the simple answer "mass".
Salinity has units of ppt, parts per thousand, such as mg/kg. It is a mass per mass unit. Thus, it fits clue #2 because we already determined mass is not impacted by temperature.
Does salinity fit clue #1? Harder...
Like many things in science, what seems like a simple definition on the surface really breaks down to uncertainty when you look deeper and deeper at it. Is salinity really just dissolved salts? Only dissolved salts? The general practical answer for seawater is that it doesn't matter since dissolved salts make up so much of the non water components in seawater that nothing else matters from a practical standpoint. But from a theoretical standpoint, does helium contribute to salinity? Why or why not? Just because it is not charged? What about boron. There is more boron as neutral B(OH)3 than as borate. Do we count it? If we dried out seawater, it would be there as weight. What about uncharged organics? Silica? Some authors seem to use seawater solids and salts interchangeably in the same paragraph, but that's obviously not the case.
Back to helium. Does it count in seawater salinity? You cannot dry out seawater and retain the helium, but it also turns out that you cannot fully dry seawater without losing some of the ions (which we presume certainly count). That is because some of the water binds strongly to the ions as they dry out, and that last bit of water is actually harder to removed than some of the ions that can shift to uncharged forms and escape to the air. Examples are HCl (from chloride and H+) and CO2 (from breakdown of carbonate).
There's no definition of seawater that would formally include helium since as a practical matter, it is never important, so no one bothers to consider it. If, as has been the formal case for the past 60 years, we take salinity to be defined as determined by conductivity, then uncharged molecules, from boric acid to silica to helium, do not contribute. This is a failing of that definition, though not one of any practical significance for actual seawater.
For purposes of this question, I'm choosing to define salinity as the mass of all dissolved nonwater components of seawater. That may not be anyone else's definition, but I think it makes great sense, and perhaps someday every chemical oceanographer will use this definition. lol
