Question

What is hydrophobicity? What is hydrophilicity? How does the hydrophobicity/hydrophilicity of a substance influence the solvents that can dissolve them?

Answer 1

Hydrophobicity : The tendency of non-polar molecules to interact with one another in a polar solvent, usually water is termed as hydrophobicity. When hydrophobic molecules are mixed with water, they will tend to separate into distinct phases (or layers), one containing water and the other containing the hydrophobic molecule.

Hydrophilicity : The molecules which are easily dissolved in water are termed as hydrophilic molecules. These molecules are polar in nature, i.e., they have a slightly negative or positive charge on their atoms which interact with the slightly positive or negative hydrogens and oxygen of water respectively which will lead to their dissolution in water.

Hydrophobicity and Hydrophilicity of a substance influences the solvents by forming Hydrogen bonds. An hydrophobic molecules will form hydrogen bonds with other hydrophobic molecules with the polar solvent such as water surrounding forming a cage of sorts with the hydrophobic molecule inside it. An hydrophilic molecule on the other hand will interact with the polar solvent such as water by forming hydrogen bonds, thus will readily dissolve in it. The unifying principle that is followed throughout chemistry and biology is that "Like dissolves like", meaning that a hydrophobic/non-polar molecule will dissolve in a non-polar solvent and vice-versa.