The first major property of water that allows absorption by plants is its liquid structure; because it is liquid at sea level and at below-freezing temperatures, a plant's root system can easily absorb and process it without expending energy melting or condensing it. Liquid water passes through the skin of the roots and it enters some cells while passing between others, depending on the cell structure and function.
The other important property of water is its high surface tension; this is vital to capillary action in plants. As the roots pass the water to the stem of the plant, it must travel against gravity and rise to the leaves and upper structures of the plant. Without surface tension keeping the water attached to itself, and to the containing surface, it could not rise up the thin capillary tubes.