Apply polarity and attraction rules to molecular mixtures and solutions.
Method and worked examples
A solution is a homogeneous mixture at the particle scale. The solvent is the dissolving medium and the solute is dissolved in it. Miscible liquids form one liquid phase in all proportions; immiscible liquids form separate layers over the relevant composition range. Dissolving does not necessarily produce ions or a chemical reaction. Sugar molecules can disperse among water molecules while remaining neutral molecules.
Polar or hydrogen-bonding solutes often dissolve in water; non-polar solutes favour non-polar solvents. A longer non-polar hydrocarbon region can reduce water solubility despite an O–H group. Emulsifiers have both polar or ionic and non-polar regions, helping stabilise mixtures of oil and water. A molecular non-electrolyte solution lacks the mobile ions needed for substantial ionic conduction.
Example 1
Why can ethanol mix with water?
Its O–H group can hydrogen-bond with water and its small hydrocarbon region does not prevent favourable mixing.
Example 2
Classify dissolved sucrose particles in water.
Sucrose is present mainly as intact neutral molecules; dissolving it does not automatically split it into ions.
Watch out:Many molecular solutes remain neutral molecules and form non-electrolyte solutions.
Miscibility and molecular solutions | Year 11 Chemistry | Ascent Arcade