Asubstance is found to be reactive, flammable, soluble, and explosive. which of these observations is a physical property?

The answer would be soluble. Think of it like salt. On it's own it is the white substance that you can see, but when you put it in water and stir it disappears. It is still there, but the physical appearance has changed. Also being explosive, flammable, and reactive are all chemical properties. Hope this helped!

Soluble would be the best answer because its like mixing salt in wanter and it would be a physical change