There are a lot of different mechanisms but basically the water and acid together form a weak bond that is harder to freeze than each separately until it reaches a point that the ideal ratio is passed over, then the trend reverses, and the jumps are the molecules becoming reactive again because it turns out Sulfuric Acid is pretty volatile stuff. Also, when fully dissolved, the atoms of some molecules can lose their ionic bonds and instead bond loosely with the water itself, allowing them to have different properties than the solute alone and that would explain why a solution of many elements would have multiple peaks on a graph of their properties.