Key Difference – True Solution vs Colloidal Solution
True solution and colloidal solution are two types of solutions based on their distinct properties. True solution and colloidal solution differ in many properties such as particle size, appearance of the solution, filterability, and visibility. These mainly arise due to the differences in solute particles sizes. The key difference between true solution and colloidal solution is, the nature of the true solution is homogeneous in contrast to the colloidal solution, which is a heterogeneous mixture.
What is a True Solution?
True solutions are homogenous solutions containing a mixture of two or more substances dissolved in a solvent. The particle size of the solvent is less than 10-9m or 1 nm. A simple example for a true solution is a solution of sugar in water. The particles in a true solution are not visible to naked eye, and those particles cannot be filtered through filter papers. The particles in a true solution do not settle on standing since they completely dissolve in the solution. Therefore, they cannot be separated by ordinary filtration.
What is a Colloidal Solution?
Colloidal solutions are heterogeneous mixtures, and the particle size of the substances in the solution is in between that of true solutions and suspensions. It ranges from 1nm to 1000 nm. The smoke arising from a fire is an example of a colloidal system where tiny particles of solid float in the air. Similar to true solutions, the particles in a colloidal solution cannot be seen with the naked eye. But, those particles are large enough to be blocked by a parchment paper or by an animal membrane.
What is the difference between True Solution and Colloidal Solution?
Properties of True Solution and Colloidal Solution:
Homogeneous vs. Heterogeneous
True Solution: A true solution contains a homogeneous mixture of two or more substances.
Colloidal Solution: A colloidal solution looks like a homogeneous solution, but it is a heterogeneous-mixture.
Particle Visibility:
True Solution: The solute particles of a true solution cannot be seen even with a microscope.
Colloidal Solution: The particles in a colloidal solution can be seen only with a powerful microscope.
Particle Size:
True Solution: The size of particles in a true solution is about 10-10 m.
Colloidal Solution: The size of solute particles in a colloidal solution is between 1 – 100nm.
Separation of Substances:
True Solution: The constituents in a true solution cannot be separated by filtration.
Colloidal Solution: The constituents of a colloid cannot be separated by filtration. However, they can be made to settle by centrifuging and then filtering by special filters.
Tyndall Effect:
True Solution: True solutions do not show Tyndall effect. (Do not scatter light)
Colloidal Solution: Colloidal solutions show Tyndall effect. (It is also known as “Tyndall scattering”, is light scattering by particles in a colloid or else particles in a very fine suspension)
Examples of True Solution and Colloidal Solution:
True Solution: When we put substances such as salt, sugar in water, they completely get dissolved to form homogeneous solutions. In other words, these solute molecules uniformly disperse in water. Particles in true solutions are of molecular size, and they are invisible. Moreover, these particles do not settle on standing. Examples of true solutions are:
- Solution of common salt in water
- Solution of sugar in water
- Sugar and alum
Colloidal Solution: Some substances are completely soluble in solutions (sugar in water), and some are completely insoluble (sand in water). There is an intermediate category in between these two types; those particles are bigger in size than molecules and smaller than suspension particles. They are visible under a powerful microscope. Some examples of colloidal solutions are,
- Starch in water
- Egg albumin in water
Image Courtesy:
1. Salt in water solution By Chris 73 / Wikimedia Commons, [CC BY-SA 3.0], via Wikimedia Commons
2. Cornstarch mixed with water By Picasa author kalaya [CC BY-SA 3.0], via Wikimedia Commons
