Suspensions

Suspension is a heterogeneous mixture of a fluid that contains solute particles that are considerably large for the process of sedimentation. Suspensions are considered to be heterogeneous in nature because they contain at least two different substances. The particles in a suspension are easily visible to the naked eye. The particles are pulled down to the bottom of the container containing the dispersion medium (water). Some of the particles in the suspension sediment to the bottom when the mixture is left. However, suspensions are mixtures where the particles do not settle. 

Suspension Definition

The size of the particles is generally larger than the particles forming the solution, usually ranging up to one micrometre. The typical diameter in the case of dispersed particles in a suspension is generally 1000 times greater than that of a solution. Since the dissolved particles are larger in size, therefore, they don’t pass through the filter paper. Hence, the physical separation technique of filtration can be used to separate the suspended particles. 

Characteristics and Properties of Suspension

Various properties and characteristics of the suspension are,

• A heterogeneous mixture is composed of two or more substances.
• Shows the Tyndall effect due to the large size of the particles.
• Suspensions are not stable. This is because the particles sediment to the bottom of the solution is left untouched for a while.
• The particles in the suspension can be separated through physical methods, like the process of filtration.
• Particles of the solute, in the case of suspension, do not dissolve in the solvent. They remain suspended in bulk throughout the suspension.
• Suspensions are opaque in nature.
• Dispersed particles are easily visible to the naked eye. The particle size is greater than 1 nanometer.
• When the particles settle, it doesn’t scatter light on them.

Examples of Suspension

Some common examples of suspension are as follows: 

• Oil shook in the water: Oil shaken in water forms a suspension owing to the difference in nature of the substances forming the suspension. Water molecules are polar in nature, which makes them attracted to each other strongly. This is in reverse to the nature of oil particles, which are nonpolar, or hydrophobic, repelling the water molecules. The water molecules display “stickiness”, which is observed in the movement of two water droplets toward each other. When left undisturbed, the suspension separates out both types of particles.
• Muddy water
• Milk of magnesia
• Sand particles suspended in water

• Dust in the air: This is an example of a solid-gas suspension. The dust particles contain different kinds of particles, like pollen grains or hair. These particles are light in weight and therefore, lifted by wind and ventilation systems. The particles are scattered throughout the air, thereby forming a suspension. These particles eventually settle down to the bottom of the earth.
• Flour in water
• Slaked lime for whitewashing
• Paints in which dyes are suspended in turpentine oil.
• Soot in the air: Soot is composed of carbon particles emitted through the process of combustion of coal and other carbon-rich energy sources. Also known as black smoke, the soot forms a solid-gas suspension in the air. This is visible in power plants as well as vehicles. The blackening of chimneys is a result of the settling down of soot.

What is a Solution?

A homogenous mixture of the materials in which the solute particle is dissolved evenly and the average size of the solute particles is less than 1 nm is called a solution. A solution has two components a solute and a solvent. The substance which is in lesser quantity and is generally solid or liquid is called a solute where as the solvent quantity is always greater and it is generally in the liquid state.

Properties of Solution

Various properties shown by the solutions are,

• Solution is a homogenous mixture i.e. all its solute particles are distributed evenly.
• Solution has particles with an average size of less than 1 nm in diameter.
• Naked eye is incapable of viewing the particles of the solution.
• Physical methods such as filtration and other are not capable of separating the solute particles from the solution.

Learn more about Solution

What is a Colloid?

A homogenous mixture of the materials in which the solute particle is dissolved has a diameter in the range of 1 nm to 1000 nm is called the colloid solution. A colloid shows a special property called the Tyndall effect which differentiates it from solution or suspension. A colloid solution has two components the component which is in lesser quantity is called the dispersed phase and the substance which is in higher quantity is called the dispersed medium.

Based on the dispersed phase and dispersed medium colloids are of various types and some of them are,

• Sols: When the dispersed phase is solid and the dispersed medium is liquid Sol is formed, for example, Paint is a sol.
• Aerosols: When the dispersed phase is either solid or liquid and the dispersed medium is air Aerosol is formed, for example, Fog is an aerosol.
• Emulsion: When the dispersed phase is liquid and the dispersed medium is also liquid Emulsion is formed, for example, butter in an emulsion.
• Gel: When the dispersed phase is liquid and the dispersed medium is solid Gel is formed, for example, jelly in a gel.

Learn more about Colloids

Difference between Suspension, Colloids, and Solution

Property	Suspension	Colloids	Solution
Particle size	Homogeneous	Homogeneous	Homogeneous
Homogeneous/ Heterogeneous Tyndall Effect Brownian	Shows	Shows	Does not Show
Movement	May or may not	Shows	Mostly do not show
Appearance	Opaque	Transparent	Transparent
Settling of particles.	Settles on their own	Settle on centrifugation	Do not settle
Separation by physical methods	Yes	No	No
Visibility	Visible with naked eyes	Not visible to the naked eye.	Visible with the naked eye.
Stability	Unstable	Stable	Stable
Examples	Flour and water mixture	Smoke, Cheese	Sugar and water solution

FAQs on Suspension

Question 1: What is a Suspension?

Answer:

Suspensions are heterogeneous systems. The particles of a suspension are very large in size, and are bigger than 100 nm to 200 nm across. These particles are easily visible through the naked eye and have a tendency to settle down under the influence of gravity. Some of the examples of suspensions are sodium chloride in benzene or turmeric in water. 

Question 2: Give some examples of suspension.

Answer:

Various examples of suspension are dust particles mixed with air, fog, milk of magnesia, and chalk dissolve in water.

Question 3: What is an Aerosol?

Answer:

A suspension that includes liquid droplets or fine solid particles as the solute dissolved in gas as the solvent is called an aerosol. Examples: fog, mist, or dust. 

Question 4: How large are particles in suspension?

Answer:

In suspension, the diameter of the particle is greater than 1000 nm and they are visible to the naked eye.

Question 5: What is the difference between suspension and colloid?

Answer:

Colloid solution is a solution in which the average size of the solution is in the range of 1 nm to 1000 nm whereas for the suspension the average size of the particle is greater than 1000 nm.