Question
Classify solutions based on the physical state of solute and solvent. List all nine possible types with one example each. Which type is most commonly encountered in chemistry problems?
(CBSE Class 12 & NEET pattern)
Solution — Step by Step
Every solution has a solvent (the component in larger amount) and a solute (the component in smaller amount). Both can exist as solid, liquid, or gas — giving us possible combinations.
We organise by solvent state first, then solute state within each:
| Solvent | Solute | Example |
|---|---|---|
| Gas | Gas | Air (O in N) |
| Gas | Liquid | Humidity (water vapour in air) |
| Gas | Solid | Smoke (carbon particles in air) |
| Liquid | Gas | Aerated water (CO in water) |
| Liquid | Liquid | Ethanol in water |
| Liquid | Solid | Sugar in water |
| Solid | Gas | H in palladium |
| Solid | Liquid | Amalgam (Hg in metal) |
| Solid | Solid | Brass (Zn in Cu) |
Liquid solvent + solid solute (like salt in water) dominates board and entrance exam problems. This is because colligative properties, Raoult’s law, and molarity/molality calculations all assume a liquid solution.
Solid-in-solid solutions (alloys) appear in metallurgy questions, and gas-in-liquid solutions show up in Henry’s law problems.
Why This Works
The classification is purely based on phases. When a solute dissolves in a solvent, the resulting mixture is homogeneous at the molecular level — that’s what makes it a solution rather than a suspension or colloid.
The reason we get exactly nine types is combinatorics: 3 states for solvent times 3 states for solute. In practice, liquid solutions are studied the most because they show the richest variety of concentration-dependent properties.
graph TD
A[Solution] --> B[Gas Solvent]
A --> C[Liquid Solvent]
A --> D[Solid Solvent]
B --> B1["Gas in Gas<br/>e.g. Air"]
B --> B2["Liquid in Gas<br/>e.g. Humidity"]
B --> B3["Solid in Gas<br/>e.g. Smoke"]
C --> C1["Gas in Liquid<br/>e.g. Soda water"]
C --> C2["Liquid in Liquid<br/>e.g. Ethanol-water"]
C --> C3["Solid in Liquid<br/>e.g. Sugar solution"]
D --> D1["Gas in Solid<br/>e.g. H₂ in Pd"]
D --> D2["Liquid in Solid<br/>e.g. Amalgam"]
D --> D3["Solid in Solid<br/>e.g. Brass"]Alternative Method — Classify by Solute State
Some textbooks organise by solute state instead of solvent state. The table is the same, just read column-wise instead of row-wise. For MCQs, the solvent-first approach is faster because the question usually tells you the solvent state.
For NEET and CBSE boards, remember these three examples cold: air (gas-gas), aerated water (gas-liquid), and brass (solid-solid). These are the most frequently tested solution types in MCQs.
Common Mistake
Students often confuse amalgam as a liquid solution because mercury is liquid at room temperature. However, amalgam (like dental amalgam) is classified as a solid solution — mercury is the solute dissolved in a solid metal matrix. The state of the solution is what matters, not the state of the pure solute before mixing.