By how much (in picograms) does the mass of 1 mol of water at 0° c differ from the mass of 1 mol of ice at 0° c? 1 mol of water = (assuming) 1 mol of ice = 18 g = 1.8E13 pg So, is this a trick question? The logic of a trickster would tell you that there would be no difference, if one assumes ice to be water ice, and that water is typically frozen at 0 c (further how do I determine the mass of ice, if I'm not told the chemical makeup). However my question extends more to, does special relativity say anything about mass effecting temperature? Does 1 mol of water weigh more at 100 c vs 0 c? I have no attempt at solving this question, because I don't know where to start. My text book gives a basic example, that heating a balloon increases the mass of the balloon as a system, but that the balloon's atoms themselves do not increase in mass. However, it does not provide a way to determine how the mass has changed.