A mixture is a collection of different substances, which physically combines, but do not join chemically. Mixtures show different physical or chemical properties than the individual substances. Solutions and colloids are two such mixtures with different properties. In these mixtures, solid, gaseous or liquid substances mix in different ratios.
What is the Solution?
A solution is a homogeneous mixture of two or more substances. We call it a homogenous mixture because the composition is uniform throughout the solution. The components of a solution are mainly of two types, solutes and the solvent. The solvent dissolves the solutes and forms a uniform solution. So, normally solvent amount is higher than the solute quantity.
All the particles in a solution have the size of a molecule or an ion, so we cannot observe them by the naked eye. The solutions can have a colour if the solvent or the solutes can absorb visible light. However, solutions are typically transparent. Solvents may occur in a liquid, gaseous or solid state. Most common solvents are liquids. Among liquids, we consider water as a universal solvent, because it can dissolve many substances than any other solvent. We can dissolve gas, solid or any other liquid solute in liquid solvents. In gas solvents, only gas solutes may dissolve.
Nevertheless, there is a limit to the number of solutes that we can add to a certain amount of solvent. The solution becomes saturated if we add the maximum amount of the solute to the solvent. If there is a very low amount of solutes, the solution becomes diluted, and if there is a high amount of solutes in the solution, it becomes a concentrated solution. By measuring the concentration of a solution, we can get an idea about the amount of solutes in the solution.
What is Colloid?
Colloidal solution exists as a homogeneous mixture, but sometimes it is heterogeneous (e.g., milk, fog). The particles in colloidal solutions are of intermediate size (larger than molecules) compared to particles in solutions and suspensions. But, like the particles in solutions, they are invisible to the naked eye, and we cannot filter using a filter paper.
We call the particles in a colloid as dispersed material, and the dispersing medium is analogous to the solvent in a solution. According to the dispersed material and the medium, there are different types of colloids. For instance, if a gas disperses in a liquid medium, the resulting colloid is ‘foam’ (e.g., whipped cream). If two liquids combine together, an emulsion form (e.g., milk). The particles that distribute within the colloidal medium do not settle down if it is left still. Colloidal solutions are translucent or opaque. Sometimes particles in a colloid can separate out via centrifugation or coagulation. For example, the proteins in milk coagulate when we supply heat or if we add an acid.
What is the Difference Between Solution and Colloid?
Solutions and colloids are two types of mixtures containing two or more substances. These mixtures are in the liquid state. However, the key difference between solution and colloid is that the the particles in a colloid are often bigger than the solute particles in a solution. Moreover, the solutions are completely homogenous compared to colloids, which also can exist as a heterogeneous mixture. Hence, this is another difference between solution and colloid. Furthermore, one other difference between solution and colloid is that the colloidal are either opaque or translucent, but solutions are transparent.
Summary – Solution vs Colloid
Both solutions and colloids are mixtures of two or more substances. The key difference between solution and colloid is that the particles in a colloid are often bigger than the solute particles in a solution.