It takes a lot of energy to drive off this water - which is what has to happen before the wood can burn. So green wood is hard to light, doesn't produce much heat, and smokes a lot. At one extreme, some professional firewood suppliers use wood kilns to dry wood in only a few days. At the other extreme, unsplit, improperly stacked wood will rot long before it is ever dry enough to use. However, be aware that the density and weight of wood also depends on the species.
White oak is denser and heavier than white pine.
Still, dry white oak is lighter than wet white oak. The bark is loose. As wood dries it tends to lose its bark. This is not an absolute rule, but when your wood is dry you should notice a good bit of barkless wood and free pieces of bark. The color of the wood fades.