What is suspension ?

 

A suspension is a heterogeneous mixture in which the solute particles do not dissolve but remain suspended throughout the bulk of the medium. Particles of a suspension are visible to the naked eye.

 

Properties of suspension

 

1. A suspension is a heterogeneous Mixture
2. The particles of a suspension can be seen by the naked eye.
3. The particles of a suspension scatter a beam of light passing through it and make its path visible.
4. The solute particles settle down when a suspension is left undisturbed, that is, a suspension is unstable. They can be separated from the mixture by the process of filtration. When the particles
   settle down, the suspension breaks and it does not scatter light anymore.

 

What is a Solution?

 

A solution is a homogeneous mixture of two or more substances. You come across various types of solutions in your daily life. Lemonade, soda water, etc. are all examples of solutions. Usually, we think of a solution as a liquid that contains either a solid, liquid, or a gas dissolved in it. But, we can also have solid solutions (alloys) and gaseous solutions (air). In a solution, there is homogeneity at the particle level. For example, lemonade tastes the same throughout. This shows that particles of sugar or salt are evenly distributed in the solution.

 

A solution has a solvent and a solute as its components.

 

The component of the solution that dissolves the other component in it (usually the component present in a larger amount) is called the solvent. The component of the solution that is dissolved in the solvent (usually present in lesser quantity) is called the solute.

 

Some examples of solutions are: Aerated drinks like soda water etc., are gas in liquid solutions.

 

These contain carbon dioxide (gas) as solute and water (liquid) as solvent. A solution of sugar in water is solid in a liquid solution. In this solution, sugar is the solute and water is the solvent.

 

Properties of a solution

 

1. A solution is a homogeneous mixture.
2. The particles of a solution are smaller than 1 nm (10-9 meters) in diameter. So, they cannot be seen by naked eyes.
3. Because of the very small particle size, they do not scatter a beam of light passing through the solution. So, the path of light is not visible in a solution.
4. The solute particles cannot be separated from the mixture by the process of filtration. The solute particles do not settle down when left undisturbed, that is, a solution is stable.

 

What is a Colloidal Solution?

 

In a colloidal solution, the particles of a colloid are uniformly spread throughout the solution.

 

Due to the relatively smaller size of particles, as compared to that of a suspension, the mixture appears to be homogeneous.

 

But actually, a colloidal solution is a heterogeneous mixture, for example, milk. Because of the small size of colloidal particles, we cannot see them with naked eyes.

 

But, these particles can easily scatter a beam of visible light as shown here.

 

This scattering of a beam of light is called the Tyndall effect after the name of the scientist who discovered this effect. Tyndall effect can also be observed when a fine beam of light enters a room through a small hole. This happens due to the scattering of light by the particles of dust and smoke in the air

 

Tyndall effect can be observed when sunlight passes through the canopy of a dense forest. In the forest, mist contains tiny droplets of water, which act as particles of colloid dispersed in the air.

 

Properties of a colloid

 

1. A colloid is a heterogeneous mixture.
2. The size of particles of a colloid is too small to be individually seen by naked eyes.
3. Colloids are big enough to scatter a beam of light passing through them and make their path visible.
4. They do not settle down when left undisturbed that is a colloid is quite stable

 

They cannot be separated from the mixture by the process of filtration. But, a special technique of separation known as centrifugation (perform activity 2.5), can be used to separate the colloidal particles. The components of a colloidal solution are the dispersed phase and the dispersion medium. The solute-like component of the dispersed particles in a colloid form the dispersed phase, and the component in which the dispersed phase is suspended is known as the dispersing medium. Colloids are classified according to the state (solid, liquid, or gas) of the dispersing medium and the dispersed phase.

 

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