D2.3.9 - Higher Level

• Water potential allows us to predict the direction in which there will be net movement of water molecules.
• Water moves from a higher to a lower water potential because this minimizes its potential energy.
• In a similar way rocks roll down hills, and atoms form chemical bonds with each other with minimization of potential energy as the motivator.
• The range of water potentials found in cells is rather unusual —the maximum value is zero.
• Cells either have a potential of 0 kPa or a negative value, for example -200kPa in a leaf cell.
• Lower water potentials are therefore more negative.
• Water will move from a cell with a water potential of -200kPa to one with - 300kPa, for example.