Water moves from the soil to the roots via the process of osmosis. The water potential in the soil is more than in the cytoplasm of the root hair. So water passes across the semi-permeable membrane of the root hair cell into the root via osmosis. Then the water is passed on to the xylem vessels where water either would travel through cortex or would go through the cell walls. Now the water keeps on moving upwards via the xylem vessels by diffusion due to the water potential gradient present. The water upon moving to the leaves, it diffuses to the mesophyll cells then into the spaces between the cells after which it vaporizes out through the stomata via the process of transpiration (loss of water from the aerial parts of the plant in form of water vapour). This whole process is driven by capillarity and root pressure. The driving force is the water potential that is established.