It doesn't have physical properties because it isn't physical. I'm not going to play that game of "defining" a non-physical entity so you can cause a distraction by picking apart the definition. I would think that people who claim to have scientific minds would not be so narrow-minded as to think that because you can't see something and define it, that it couldn't exist. Science is supposed to be open to all possibilities, is it not?You first need to define your terms regarding this "spirit" thing. Metaphysics and mysticism aside, this "spirit" you claim exists has no properties which can be quantified.If man did not possess a spirit, death would not be final. The body could be repaired, the heart jump started, and the patient would be up and running again. The body is the car, and the spirit is the driver. Without the driver, the car is just a bunch of metal. Call that driver anything you want, but it's not physical.
Then the obvious question is "Where does the spirit come from and how did it get in the body"? It had to come from somewhere.
Your mind seems to be sealed shut.