Final answer:
In a lipid bilayer, the hydrophobic tails of phospholipids energetically avoid interacting with water by facing inward, away from the water, and the hydrophilic heads face outward.
Step-by-step explanation:
In a lipid bilayer, lipids energetically prefer to have their hydrophilic (water-loving) heads in contact with water, while keeping their hydrophobic (water-fearing) tails away from water and sequestered in the interior of the bilayer. The hydrophobic tails do not want to interact with water since these lipid regions are nonpolar. As a result, phospholipids in the cell membrane arrange themselves to prevent any contact between their hydrophobic tails and water, thus forming the characteristic bilayer structure where the tails face inward, protected from water, and the hydrophilic heads face outward.