When in the presence of water, how does a phospholipid orient itself? what property of water initiates this reaction?

Phospholipids are the lipids containing phosphate group. It is composed of two main units, one is the glycerol unit/fatty acid unit (non-polar unit) and another is the phosphate unit (polar unit).

When phospholipids are placed in water the two groups orient themselves to form a bilayer with phosphate group which is hydrophilic in nature facing outward and the glycerol unit/ fatty acid unit which is hydrophobic in nature facing inwards.

The cohesive nature of water that is its formation of hydrogen bonding initiates the process of formation of bilayer.

a. energy is absorbed in the reaction.

if in a given reaction the energy of products is greater than the energy of reactants it means that reaction is endothermic and during the reaction, the energy is absorbed by reactants. in an endothermic reaction, the products have more stored chemical energy than the reactants. and in this reaction the reactants are more stable than products before the compounds with less energy are always more stable.