Suspensions and Colloids: You are provided with two beakers \({\rm{A}}\) and \({\rm{B}}.\) Beaker \({\rm{A}}\) contains milk, and beaker \({\rm{B}}\) contains sand in water. Which of these is homogeneous and heterogeneous? Yes, both are heterogeneous mixtures. Here beaker \({\rm{A}}\) is a colloidal solution, and beaker \({\rm{B}}\) is the suspension.

A suspension is a heterogeneous mixture in which some particles settle out after a period of time. Because the particles in a suspension are much bigger than those in a solution, gravity can pull them out of the dispersion medium (water). A colloid is a heterogeneous combination with scattered particles that are between those of a solution and those of a suspension in size. The particles are evenly distributed across the dispersion medium, which might be a solid, liquid, or gas. 

In this article, you will indulge in the meaning, example, property, comparison and difference between the suspension and colloids. Continue reading to know more.

What are Colloids?

Colloids are heterogeneous systems having a particle size ranging from \({\rm{1}}\,{\rm{nm – 1000}}\,{\rm{nm}}.\) It consists of two phases, i.e., dispersed phase and dispersion medium.

Some examples of colloids are cheese, butter, jellies, some paints, cell fluids, etc.

Dispersed phase: The substance present in the form of colloidal particles in the colloidal system is called the dispersed phase.

Dispersion medium: The medium in which the colloidal particles are dispersed is called dispersion medium.

Example: In a colloidal solution of ferric hydroxide in water, ferric hydroxide is the dispersed phase, and water is the dispersion medium.

What are the Properties of Colloids?

Colloids shows the following properties:

1. Colloids are heterogeneous in nature.
2. The particle size of the colloid is between \({10^{ – 9}}\) to \({10^{ – 6}}\;{\rm{m}}\) or \(1\;{\rm{nm}}\) to \(1000\;{\rm{nm}}\) or \({\rm{10}}\;\mathop {\rm{A}}\limits^{\rm{o}} \) to \({\rm{10000}}\;\mathop {\rm{A}}\limits^{\rm{o}} .\)
3. Colloidal particles do not settle under gravity. However, they can be made to settle under high-speed centrifugation.
4. Colloids pass easily through ordinary filter paper but not through the animal membranes.
5. Scattering of light by the colloidal particles is observed under an ultra-microscope.
6. The diffusion of the colloidal particles is slow.
7. Colloids are generally transparent but may show translucence.
8. It exhibits both the Tyndall effect (scattering of light by colloidal particles) and Brownian movement (zig-zag movement of colloidal particles).

Study The Classification Of Colloids

What are Suspensions?

Suspensions are heterogeneous systems having small insoluble particles. The particle size is more than \(1000\;{\rm{nm}}\left( { > {{10}^{ – 6}}\;{\rm{m}}} \right).\) These particles are either visible to the naked eye or can be seen under a microscope. The particles of a suspension can neither pass through an ordinary filter paper nor through the animal membrane.

Example: Stirred muddy water, dirt particles in water, etc.

What are the Properties of Suspension?

Suspension shows the following properties:

1. Suspensions are heterogeneous in nature.
2. The particle size of the suspension is more than \({{{10}^{ – 6}}\;{\rm{m}}}\) or more than \({\rm{10000}}\;\mathop {\rm{A}}\limits^{\rm{o}} .\)
3. Suspensions settle under gravity.
4. These do not pass-through ordinary filter paper or not through an animal membrane.
5. Particles are visible to the naked eye or under a microscope.
6. Suspension does not diffuse.
7. Suspensions are opaque in nature.
8. All suspensions exhibit the Tyndall effect, and some suspensions may show the Brownian movement.

What is a True Solution?

A homogeneous system having the diameter of the dispersed particle less than \(1\;{\rm{nm}}\left( {{{10}^{ – 9}}\;{\rm{m}}} \right).\) The particles of solute present in a true solution are either single molecules or ions and these are homogeneously distributed throughout the solution. These particles are invisible and cannot be seen even with a microscope.

Examples: Salt in water, sugar in water, urea in water, etc.

Properties of the True Solution

The true solution shows the following properties:

1. It is homogeneous in nature.
2. The particle size of the is less than \(1\;{\rm{nm}}\left( {{{10}^{ – 9}}\;{\rm{m}}} \right).\)
3. The true solution does not settle.
4. These pass easily through ordinary filter paper as well as through animal membranes.
5. It does not scatter the light.
6. The diffusion of the true solution is rapid.
7. It is transparent.
8. It does not exhibit both the Tyndall effect and Brownian movement.

Distinguishing Features of True solution, Colloidal Solution, and Suspension

	Property	True solution	Colloid solution	Suspension
1.	Particle size	\( < 1\;{\rm{nm}}\left( {{{10}^{ – 9}}\;{\rm{m}}} \right)\)	\({10^{ – 9}}\) to \({10^{ – 6}}\;{\rm{m}}\) or \(1\,{\rm{nm}}\) to \(1000\;{\rm{nm}}\)	\({\rm{ > 1000\;nm}}\left( {{\rm{ > 1}}{{\rm{0}}^{{\rm{ – 6}}}}} \right.{\rm{m)}}.\)
2.	Nature	Homogeneous	Heterogeneous	Heterogeneous
3.	Filterability	Pass through both ordinary filter paper and animal membrane	pass easily through ordinary filter paper but not through an animal membrane	It does not pass through ordinary filter paper as well as through animal membrane
4.	Settling of particles	Does not settle	Settle only on centrifugation	Settle under gravity.
5.	Visibility	Particles are invisible	Particles are observed under ultramicroscope	Particles are visible to the naked eye or under a microscope.
6.	Appearance	Transparent	Generally transparent but may show translucence	Opaque
7.	Diffusion of particles	Diffuse rapidly	Diffuse slowly	Does not diffuse
8.	Tyndall effect	Does not show	Shows	Shows
9.	Brownian effect	Negligible	Shows	May show

Activity for Solutions, Suspensions and Colloids

The mixture can be separated as a solution, suspension and colloid based on the settling property of particles. If the given mixture is a suspension, it settles due to gravity. Whereas colloid settles only by centrifugation, but particles of true solution do not settle.

Example: In the mixture of salt in water, sand in water and milk, salt in water is a true solution, sand in water is the suspension, and milk is the colloid.

Summary

In this article, you have grasped an idea about meaning, examples and properties of colloid, suspension, and true solution in detail. With this article, you can differentiate colloid, suspension, and true solution. You can also identify colloid, suspension, and true solution with suitable activity. This article will be a basis for further detailed study of each solution, i.e., colloid, suspension, and true solution.

Frequently Asked Questions

We have provided some frequently asked questions here:

Q.1. Write five examples of the true solution, suspension, and colloid.
Ans: Examples of True solution: Salt in water, sugar in water, air, vinegar and alloy like brass.
Examples of suspension: Stirred muddy water, dirt particles in water, chalk powder in water, sand in water and milk of magnesia.
Examples of colloid: Cheese, butter, jellies, some paints, and cell fluids.

Q.2. What is suspension?
Ans: Suspensions are the heterogeneous system having small insoluble particles of the particle size more than \(1000\;{\rm{nm}}\left( { > {{10}^{ – 6}}\;{\rm{m}}} \right)\).
Example: Stirred muddy water, dirt particles in water.

Q.3. What are the colloids?
Ans: Colloids are heterogeneous systems having a particle size ranging from \(1\;{\rm{nm}} – 1000\;{\rm{nm}}\).
Example: Milk, butter, etc.

Q.4. How big are the particles in a colloid compared to those of a suspension and a true solution?
Ans: The size of the colloidal particles is \({\rm{1}}{{\rm{0}}^{{\rm{ – 9}}}}\) to \({\rm{1}}{{\rm{0}}^{{\rm{ – 6}}}}{\rm{\;m}}\) (\({\rm{1\;nm}}\) to \({\rm{1000\;nm}}\)), whereas the size of the true solution is less than \(1\;{\rm{nm}}\left( {{{10}^{ – 9}}\;{\rm{m}}} \right)\) and size of suspension is more than \({10^{ – 6}}\;{\rm{m}}(1000\;{\rm{nm}}).\)

Q.5. If you add a large spoonful of salt to a glass of standing water, the salt sinks to the bottom. Is this a suspension? Explain.
Ans: No, on adding salt to a glass of standing water, initially salt sinks to the bottom due to the high mass of salt particles, but slowly, salt dissolves in water and forms a homogeneous solution. This is an example of a true solution.

Q.6. Write three points of difference between true solutions, suspensions and colloids.
Ans:

	Property	True solution	Colloid solution	Suspension
1.	Particle size	\( < 1\;{\rm{nm}}\left( {{{10}^{ – 9}}\;{\rm{m}}} \right)\)	\({10^{ – 9}}\) to \({10^{ – 6}}\) or \(1\;{\rm{nm}}\) to \(1000\;{\rm{nm}}\)	\( > 1000\;{\rm{nm}}{\left( { > {{10}^ – }} \right.^6}{\rm{m}}).\)
2.	Nature	Homogeneous	Heterogeneous	Heterogeneous
3.	Settling of particles	Does not settle	Settle only on centrifugation	Settle under gravity.

Learn About Application of Colloids

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