The function of cilia and flagella move liquid past the surface of the cell. For single cells, such as sperm, this enables them to swim. For cells anchored in a tissue, like the epithelial cells lining our air passages, this moves liquid over the surface of the cell (e.g., driving particle-laden mucus toward the throat).
a) If the solvent-solute interactions in a mixture are <u>stronger than</u>the solvent-solvent interactions and the solute-solute interactions, a homogeneous solution forms.
b) If the solvent-solute interactions in a mixture are <u>weaker than</u> the solvent-solvent interactions and the solute-solute interactions, the formation of a homogeneous solution is uncertain.
The solubility of solute in given solvent mainly depends upon the intermolecular interactions between the solvent and the solute. If the solute is surrounded and solvated by the solvent then the solute will dissolve in that solvent. Therefore, in order to dissolve the solute must form stronger interactions with the solvent as compared to the solute solute interactions or solvent solvent interactions.
When NaCl is added to water the partial negative oxygen of water is attracted to Na⁺ of NaCl and the partial positive hydrogen of water is attracted to Cl⁻ of NaCl. These new interactions between the NaCl ions and water are stronger than the interactions between water molecules and NaCl molecules themselves hence, results in solubility of NaCl in water.
On the other hand, if NaCl is added to Hexane (C₆H₁₄) it fails to make strong interactions with the solvent molecules resulting in insolubility of NaCl in hexane.