How do phospholipids give the cell membrane the self-sealing property?

Because lipid bilayers are held together by many reinforcing, noncovalent interactions (predominantly hydrophobic), they are cooperative structures. These hydrophobic interactions have three significant biological consequences: (1) lipid bilayers have an inherent tendency to be extensive; (2) lipid bilayers will tend to close on themselves so that there are no edges with exposed hydrocarbon chains, and so they form compartments; and (3) lipid bilayers are self-sealing because a hole in a bilayer is energetically unfavorable.

How do phospholipids give the cell membrane self-sealing property?

See above

Ok thanks.
Do you know why water soluble substance cannot pass through the cell surface membrane?

Because of the hydrophobic core, the layer is not permeable to large polar molecules.

Is this because the hydrophobic tails repel the polar molecules?