Final answer:
Polar and nonpolar substances have different abilities to mix. Nonpolar substances can mix with other nonpolar substances, while polar substances can mix with other polar substances. However, polar and nonpolar substances do not mix easily with each other. Small nonpolar molecules can passively diffuse across the plasma membrane, while polar substances and ions require special means of transport.
Step-by-step explanation:
Polar and nonpolar substances have different abilities to mix. Nonpolar substances can mix with other nonpolar substances, while polar substances can mix with other polar substances. However, polar and nonpolar substances do not mix easily with each other due to their different properties.
When it comes to passing across the plasma membrane, small nonpolar molecules, such as oxygen and carbon dioxide, can passively diffuse through the membrane by simple diffusion. In contrast, polar substances and ions cannot easily cross the membrane due to the hydrophobic core of the lipid bilayer. For the diffusion of polar substances, such as glucose and amino acids, and ions like sodium and potassium, the plasma membrane requires special means of transport provided by transmembrane proteins.