Question

why does water potential decrease when placed in high concentration?

Answer 1

High concentration means that the amount of ions present in a solute is more (so water is less) thus water potential decreases.

Normally if a substance has high water potential it also indicates that its concentration is low and vice versa.

Answer 2

water potential decrease because when we place it in high concentration , its turgor pressure or pressure potential will decrease as water will move out of the cell [hypertonic solution] causing its water potential to decrease [  because water potential is equal to solute potential and pressure potential]

Answer 3

Water potential is the chemical or potential energy of water molecule . The water potential of pure water is zero. When solute added the solute molecule occupy

 more space between the water molecules that reduce the concentration of water molecule per unit of water.  Water potential is directly proportional to

 the number of water molecule per unit area, when water alone present the potential become stabilized by the intermolecular attraction between the

water molecules (Van der Waals force), but when solute is added the intermolecular attraction force between water molecule reduce and  by the

occupation of solute between them.