Ever wondered why you can view certain dust particles in the air? Or why does the solution of chalk and water contain the solid pieces to appear bulky in the solution? This naturally occurring phenomenon is known as suspension. In this article, we are going to learn and understand the explanation behind this naturally occurring phenomenon.
Suspension is strictly defined as the heterogeneous mixture of a solid and liquid wherein the solid particles are finite and appear to spread throughout the liquid instead of dissolving in it. This gives the effect of the solid particles being suspended in the liquid. In simple words, suspension occurs when the solid particles do not dissolve in the liquid and instead appear to be suspended, as seen through the naked eyes.
The solid particles dissolved in the liquid should contain a diameter greater than 1000nm; otherwise, the particles might be too fine to be viewed through naked eyes. Hence, the solid particles should not be too finite or small and large enough for sedimentation. This can be an essential property for the suspension state to take place. We can understand the concept of suspension much more efficiently with the help of the illustration, as shown below.
In the above-given figure, we can see that a solution contains an even mixture of solute and solvent. In suspension, the solution contains a heterogeneous mixture of solid particles that appear to be suspended through the liquid. In precipitation, these solid particles are transformed into an insoluble mass that settles at the bottom of the glass container. You demonstrate the example of suspension: take a glass of clear water and throw in a handful of sand or mud. Stir the mixture well enough. You might notice the water may have become turbid or unclear after this. This is because sand and mud do not dissolve in water, and even though it may look like a homogeneous solution for a few moments, the sand or mud gradually sinks to the bottom of the glass.
Famous examples of suspension can include the following solutions or heterogeneous mixtures:-
1. Milk of magnesia
2. A mixture of mud and water
3. The mixture of flour and water
4. Sand particles and water
5. The solution of slaked lime used for whitewashing
6. Dyes where the paint appear to be suspended in turpentine oil
7. A simple mixture of chalk and water
It has to be noted that the suspension does not maintain its state for an extended period. Over time, the suspension solution is converted to precipitation due to the effect of gravity. The solid particles that are spread evenly throughout the liquid seem to be settling at the bottom of the glass container they are placed in and form a mass, i.e., sediment. However, stable suspensions can form sediments with solid particles whose diameter is less than 1 µm. The reason why these fine particles are present in the suspended state is due to molecular movement. In this process of forming a mass of sediment at the bottom of flasks, glass containers, and even tanks, the solid whose diameter is less than 1 µm is known as a colloid, and the solution is known as a colloidal solution.
However, here the term “colloid” and “suspension” should not be confused for the same. There lie several differences between a colloid and suspension. Some of them are as follows:-
|A colloid is defined to be a homogenous solution where the particle range is less than 1 µm||A suspension is defined to be a heterogeneous solution where the particle size has a range greater than 1nm|
|In a colloidal solution, the particles form a mass or a sediment that is settled at the bottom of the glass container.||In a suspension solution, the particles do not form any type of mass, instead they settle down well at the bottom of the glass container.|
|Whenever a ray of light is passed through a colloidal solution, the ray of light is scattered. This effect is known as the Tyndall effect.||Whenever a ray of light is passed through a suspension solution, the ray of light may or may not be scattered.|
|The colloidal solution appears to be transparent||The suspension solution is opaque in nature.|
|A colloidal solution is not visible to the naked eye and cannot be separated out by filtration.||A suspension solution is visible to the naked eyes and can be separated out by using filtration.|