When sugar is added to water, how does the mass change, and how does that affect the water's density and boiling point? I can't find a good answer anywhere. How does the amount of sugar added change the boiling point, mass, and density of water? Does it affect the mass or the volume? Or both?
 A: As stated above, the mass of the whole system (sugar + water) doesn't change.  In addition, with "ideal" mixing, the total volume of the water plus the total volume of the sugar equals the total volume of the mixture.  However, this is not a sure bet, and there are many cases of a volume of one material mixed with a different volume of water, and the total volume is not the sum of the two.  I'm not familiar with whether or not sugar mixed with water is ideal or non-ideal ... a Google search may have some hints for this.
The following link is a good start for this kind of data:
http://homepages.gac.edu/~cellab/chpts/chpt3/table3-2.html
Regarding boiling point, the boiling point increase (and the freezing point depression) depends only on the number of particles dissolved in the solution.  The term for this is the "colligative" properties of these substances.  Table sugar is a dimer, which means that it is composed of two 6-carbon sugars.  It is easily possible that some of this dimer disassociates into its constituent parts when in solution, increasing the number of particles in solution, and hence, the boiling point.  Rather than go through calculations to determine this, there should be published data that give the measured effect.  This link should give you some good information:
http://kitchenscience.sci-toys.com/boiling_freezing_pressure
A: The mass doesn't change at all, it will be just the sum of the water mass and the mass Added, what happens is the change of density because the mixture, in general the molecules get closer to each other  ( through the intermolecular forces) and, this way, the volume become lower to the same mass quantity, what increase the density by the equation
$$
\rho = \frac{m}{V}
$$
Another effect because the changing of the intermolecular forces is the increasing of boiling temperature. It happens due the increasing of the intensity of the intermolecular force after the mixture, this way you need more thermal energy to break the bounds, and so, you need more heat to do that.
I really hope it helps you! 
