Final answer:
Water can pass through the lipid bilayer more easily than sodium ions, which require membrane transport proteins to move across the membrane. Sodium ions cannot diffuse through the hydrophobic lipid bilayer without assistance due to their charge.
Step-by-step explanation:
It is false that it is harder for water to cross a lipid bilayer than for a sodium ion to do so. Water molecules, although polar, are small enough to pass through the lipid bilayer, albeit not as readily as nonpolar molecules. In contrast, sodium ions are charged and cannot diffuse through the hydrophobic interior of the lipid bilayer on their own. Membrane transport proteins, such as ion channels, are necessary for the movement of sodium ions and other ions across the cell membrane, because they cannot pass directly through the lipid bilayer.
Passive transport
such as facilitated diffusion allows ions to pass through the membrane via transport proteins
without
expending energy. Small nonpolar molecules like oxygen and carbon dioxide, however, can diffuse more freely between the lipids in the plasma membrane due to their compatibility with the hydrophobic core.