Here's where things get fun. Just like the number of reps, 3-6 sets is the best range of volume for this training method. If you like your workouts paced like clockwork, take 30-60 seconds rest between each exercise.
The natural attraction between positive and negative keeps the ions surrounded by water molecules and therefore dissolved in solution. Many biochemicals are either polar molecules or charged ions (or both) so water makes an excellent solvent for them.
Solvent properties of water. However, this name isn't entirely accurate, since there are some substances (such as oils) that don't dissolve well in water. Generally speaking, water is good at dissolving ions and polar molecules, but poor at dissolving nonpolar molecules.