Let’s follow the fate of the soda from the time that rascal put it in the freezer, probably with the misguided intention of keeping it nice and fizzy till the next attack of thirst.
All liquids turn into solids, that is, they freeze, when they get cold enough. Pure water freezes at 32°F (0°C), but your soda isn’t pure water. Far from it.
It contains flavorings, phosphoric acid, coloring, and sweeteners, sugar, corn syrup, or artificial sweeteners.
Still, the vast majority of the molecules in the bottle are good old H2O. And when they are cold enough to freeze, they join together into a rigid network, a geometrically regular, three-dimensional arrangement of Hp molecules that we call ice.
The molecules in ice are in fact so rigidly fixed in their places that they are hard to break apart from one another. Ice is therefore (surprise!) a much harder sub- stance than liquid water.
With all those other non-H2O molecules cluttering up the place, however, the water molecules have a harder time finding one another so they can join together and form ice crystals. So the soda had to be cooled down past its normal 32-degree temperature before it was able to freeze.
But freeze it eventually did.
The water molecules eventually slowed down enough to settle comfortably into their places. As they did, they were able to elbow aside all those foreign molecules, so the ice they formed was relatively pure. That’s the white ice we see. All the “brown molecules” had been left behind.
Ice floes in the Arctic are made of relatively salt-free ice for the same reason, in spite of the fact that they were frozen from salty seawater.