Acoin is tossed into the air 500 times. approximately how many heads would you expect?

Really it matters on which head you start the flip on. Whichever head you start with, there's a 51% chance to land on that one. If you start with heads, it would be 255 times.

By water evaporation from the leaves is created a negative pressure at the top of the tree that promotes the ascension  of the water through channels that are called xylem. there are also two molecule forces that are involved: the intra-water molecules cohesion (water molecules stick to each other) and the adhesion when the water molecules stick to the channels they are running in. this is what enables water to go from the roots to the top of a tall tree.

We are not able to see the stars. light prevents our seeing the stars. i hope it kinda : )