A solution is a type of mixture in which one substance, the solute, is completely dissolved in another substance, the solvent. It means the solute breaks down into tiny particles that spread evenly throughout the solvent, creating a uniform mixture. For example, when you stir sugar into water, the sugar dissolves, forming a sweet, clear liquid. ^[1-4]

Components of a Solution

A solution consists of two main components: solute and solvent. ^[1-4]

A solute is a substance that gets dissolved in a solution. It is usually present in a smaller amount than the solvent. The solute spreads out evenly in the solvent, forming a mixture that looks the same throughout.

A solvent is the component of a solution that dissolves the solute. It is usually the component present in the largest amount in the solution. The solvent’s job is to break down the solute into smaller particles so they spread evenly, creating a uniform mixture.

Example: When sugar dissolves in water, sugar is the solute, and water is the solvent.

Characteristics of a Solution ^[1-4]

• A solution is evenly mixed so that every part of it looks the same.
• The solute is broken into pieces so small you cannot see them.
• Once the solute dissolves, it will not settle to the bottom or separate from the solvent.
• Solutions are usually clear and transparent, though they can also be colored, such as a blue copper sulfate solution.
• You cannot use a filter to separate the solute because the particles are too small.
• Even if the solute and solvent are initially in different states (e.g., a solid solute like sugar in a liquid solvent like water), the solution appears to be in a single state.
• Varying the amount of solute in a solution can adjust its concentration: more solute makes the solution more concentrated, while less solute makes it more dilute.
• The amount of solute that can dissolve depends on the solute and solvent, as well as the temperature and pressure.

Types of Solution

Solutions are typically categorized in two ways: (i) by the physical state of the solute and solvent and (ii) by the amount of solute present in the solution at a given temperature. ^[1-4]

Based on the Physical State

The following table shows the different types of solutions based on the physical state with examples.

Type	Solute	Solvent	Example
Solid-Solid	Zinc	Copper	Brass
Solid-Liquid	Salt	Water	Salt water
Solid-Gas	Sulfur	Air	Sulfur vapor in air
Liquid-Solid	Mercury	Zinc	Amalgamated zinc
Liquid-Liquid	Alcohol	Water	Alcohol in water
Liquid-Gas	Water droplets	Air	Fog
Gas-Solid	Hydrogen	Palladium	Hydrogen in palladium
Gas-Liquid	Carbon dioxide	Water	Carbonated drinks
Gas-Gas	Oxygen	Nitrogen	Air

Based on the Amount of Solute Dissolved

Solutions can be classified into saturated, unsaturated, and supersaturated types based on the amount of solute dissolved in the solvent under specific conditions, such as temperature and pressure.

Saturated Solution

A saturated solution has dissolved as much solute as it can at a certain temperature. If you try to add more solute, it will not dissolve and will stay at the bottom. For example, if you keep adding sugar to hot water, there will come a point when no more sugar will dissolve, and the solution will become saturated.

Unsaturated Solution

An unsaturated solution is a solution that can still dissolve more solute. It has not reached its limit yet. For example, if you add just one spoonful of sugar to a glass of water, the water can still dissolve more sugar, so the solution is unsaturated.

Supersaturated Solution

A supersaturated solution contains more solute than it can typically hold under normal conditions. It is prepared by heating the solution to dissolve the extra solute and then cooling it slowly. If disturbed, this delicate state can lead to precipitation. For example, when making rock candy, a supersaturated sugar solution is used to grow sugar crystals.

Application of Solutions ^[1-4]

• Beverages: Drinks like tea, coffee, juice, and soda are solutions in which water is the solvent and sugar, flavorings, or gases act as solutes.
• Cleaning Agents: Liquid detergents and soaps dissolve dirt and grease in water, helping to remove them.
• Cooking: Solutions are formed when salt or sugar is dissolved in water while cooking to enhance flavor.
• Pharmaceuticals: Many medicines are prepared as solutions, such as syrups or injectable drugs, where the solute (active drug) is dissolved in a suitable solvent.
• Food Processing: Industries use solutions to make flavored syrups, brine solutions for preserving food, or carbonated beverages.
• Chemical Industries: Solutions are used for reactions, extractions, and formulations, such as cleaning agents, paints, or fertilizers.