True Solution and its Properties

Two or more substances combine to form a mixture. A mixture can be formed between components that are solid, liquid or gas. The constituents of a mixture are not chemically bonded and are defined as a physical combination.

Based on the uniformity of the mixture, they are divided into:

1. Homogenous Mixture: This is the uniform mixture and the components of this mixture cannot be distinguished. For example: salt and water. 
2. Heterogeneous Mixture: This is a non-uniform mixture, in which the components can be physically distinguished and separated. For example: Sand and pebbles. 

What is a True Solution?

A homogenous mixture consisting of two or more substances is called True solution or simply, Solution. Two important components of the solution are Solute and Solvent. A solute is a substance that is dissolved in another substance called the solvent. 

 Based on the state of matter of the solvent and solute, solutions are of three types: 

• Liquid-Liquid- A solution in which both solute and solvent is in a liquid state. These solutions can be immiscible, completely miscible or partially miscible.
• Solid-Liquid- In this type of solution, the solid is the solute and the liquid acts as a solvent. When the amount is significantly less than the solvent, the solution is dilute and when the amount of solute is large, the solution is concentrated.
• Gas-Liquid- This solution refers to gas as the solute and liquid as the solvent. The solubility of the solute in this case is determined by several factors such as the nature of gas, temperature and pressure.

Properties of True Solution

A True Solution has the following properties: 

1. It cannot be separated by physical operation methods such as filtration, centrifugation or sedimentation. However, the solute can be obtained by crystallization or evaporation in some cases.
2. A true solution is transparent and the molecules of solute and solvent can not be distinguished.
3. Due to the small size of particles of the solution, it cannot scatter a light beam.
4. The solution can easily pass through filter paper owing to the small size of the molecules.
5. The solute retains its properties even after forming the solution. For example, sugar solution tastes sweet due to the properties of sugar molecules. 

True Solution, Colloid and Suspension 

A true solution is a homogeneous mixture, whereas colloid and suspension are examples of heterogeneous mixtures.

The molecules in a colloidal mixture are larger than those of a true solution. The size of particles is still too small to be observed by the naked eye. This mixture can pass through filter paper as well. Colloids can be reversible or irreversible based on the size of particles of the colloidal substance. Paints and dyes are irreversible whereas a colloidal mixture of polymers or proteins are reversible as they have high molecular weight.

Suspension is a heterogeneous mixture with particles large enough for sedimentation. The particles might even be visible to the naked eye as they are larger than 1mm. The particles of suspension are capable of settling down but the mixture is called suspension only before the particles settle down. A mixture of sand and water is a classic example of a suspension.

In a True Solution, the solute dissolves completely, in a colloid a uniform distribution of solute particles is observed and, in a suspension, the solute does not dissolve in the solvent.

Differences between True Solution, Colloidal Solutions and Suspension 

Some of the differences among these three are:

• A true solution is a homogeneous mixture, whereas a colloidal solution and suspension are heterogeneous.
•  A true solution is transparent, a colloid is translucent and a suspension is opaque.
• The particles of a true solution are not visible, in colloid and suspension they can be seen.
• The particles of True Solution colloid will not sediment, but a suspension will sediment. 
• True Solution diffuses quickly, a colloid diffuses slowly and a suspension does not diffuse at all. 
• True Solution can pass through both animal membrane and filter paper, colloid can pass only through filter paper and not an animal membrane, a suspension cannot pass through either of them.

Examples of True Solutions

True solutions are simple homogenous mixtures and examples of true solutions can be easily found in daily life.

• Solid-liquid: Salt and water, sugar and water 
• Liquid-liquid: Water and lemon juice, water and alcohol 
• Gas-liquid: oxygen and water, carbon dioxide and water

Conclusion 

A mixture is a combination of two or more substances. It can be homogeneous or heterogeneous.

True Solution is a homogeneous mixture and has two components- Solute and Solvent. The solution is clear and does not reflect light. The solute cannot be separated from the solution by physical methods.

A solution is different from colloidal mixtures and suspensions, which are heterogeneous.