Solid dissolved in liquid
Two examples of soild dissolved in liquid are sodium chloride dissolved in water and sucrose dissolved in water. Each forms a homogeneous solution when the solid particles become separated and dispersed throughout the liquid solvent.
Solution terminology
A solution contains a solute (the substance being dissolved) and a solvent (the substance doing the dissolving). In solid-in-liquid solutions, the solute begins as a crystalline solid and the solvent is a liquid, commonly water for aqueous solutions.
Homogeneity in a true solution is a particle-level statement: the solute is distributed uniformly on the molecular or ionic scale, even though the solute may be invisible to the eye.
Two representative examples
Example 1: sodium chloride (NaCl) dissolved in water
Sodium chloride is an ionic solid made of Na+ and Cl− ions held together by electrostatic attraction in a crystal lattice. In water, strong ion–dipole interactions between water molecules and the ions stabilize separated ions (hydration), allowing NaCl to dissolve until saturation.
Example 2: sucrose (C12H22O11) dissolved in water
Sucrose is a molecular solid. It dissolves because polar O–H groups on sucrose can form extensive hydrogen-bonding interactions with water. The crystal is disrupted as individual sucrose molecules become solvated and dispersed, again up to a saturation limit at a given temperature.
Comparison table
| Solid solute | Solvent | Particle form in solution | Dominant solute–solvent attraction | Typical observable result |
|---|---|---|---|---|
| NaCl (table salt) | H2O | Na+(aq) and Cl−(aq) | Ion–dipole (hydration) | Clear brine; conducts electricity |
| Sucrose (sugar) | H2O | Sucrose molecules (aq) | Hydrogen bonding and dipole interactions | Clear sugar solution; negligible electrical conductivity |
Concentration language that follows from these examples
Once a solid is dissolved in a liquid, concentration can be expressed in several standard ways. A common introductory form is mass percent:
\[ \%\,(m/m) = \frac{m_{\text{solute}}}{m_{\text{solution}}}\times 100\%. \]
The mass \(m_{\text{solution}}\) includes both solute and solvent, and the expression remains valid regardless of whether the solute is ionic (NaCl) or molecular (sucrose).
Visualization of particle-level dissolution
The diagram contrasts an ionic solid (NaCl) dissolving into hydrated ions with a molecular solid (sucrose) dissolving into solvated molecules. The liquid phase is depicted as a continuous medium while the solute units are shown as dispersed particles.
Common pitfalls
- Suspension versus solution: undissolved particles that settle or scatter light indicate incomplete dissolution or a suspension rather than a true solution.
- Solubility limits: adding more solute beyond saturation leaves excess solid, even when the mixture is stirred thoroughly.
- Temperature effects: many solids (including sucrose) become more soluble as temperature increases; solubility trends depend on the solute–solvent system.