<span>Taking into account the information above, we know the average mass of the bucket of water may be m=20-5/2=17.5kg. As the bucket of water is pulled at a "constant velocity" the work required to raise the bucket to the platform transformed into the potential energy of the bucket of water. That is why it should be W=mgh=17.5*9.8*40=6860J</span>
No, and no. In fact, the consequences are exactly opposite to your description.
When you drop soap on the ground, the soap ... which had been clean ... gets dirty, and the ground ... which had been dirty ... gets clean.