So fill in: sugar.

(2) Distiller's grains can be separated from red wine by filtration, and red wine needs to be boiled in a pot for a period of time before being put into an urn. At this time, you can smell the aroma of wine, indicating that the molecules are constantly moving.

Therefore, fill in: filter; Molecules are constantly moving.

(3) Plastic is an organic synthetic material. A simple way to identify whether red wine is sour is to drop a few drops of litmus test solution in red wine. If litmus test solution turns red, it means that red wine has turned sour.

So, fill in: organic synthesis; Drop a few drops of litmus test solution into red wine. If litmus test solution turns red, red wine will turn sour.