Class 9 science Solutions English Medium

Suspension: The hetrogenous mixture in which solids are dispersed in liquids, are called suspensions.

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 a Suspension: 

(i) It is a hetrogeneous mixture.

(ii) The particles of a suspension can be seen by necked eyes.

(iii) The particles of a suspension scatter a beam of light passing through it and make its path visible.

(iv) A suspension is unstable.

(v) They can be separated from the mixture by the process of filtration.

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, smoke and fog etc.

Properties of colloidal solution: 

(i) A colloid is a heterogeneous mixture.

(ii) The size of particles of a colloid is too small to be individually seen by naked
eyes.

(iii) Colloids are big enough to scatter a beam of light passing through it and
make its path visible.

(iv) They do not settle down when left undisturbed, that is, a colloid is quite
stable.

(v) They show tyndall effects. 

(vi) Colloidal particles can not be seperated by the process of filteration. 

The components of a colloidal solution: 

(i) Dispersed Phase: The solute-like component or the dispersed particles in a colloid form the dispersed phase.

(ii) dispersion Medium:  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.

See this table DIs

Tyndall Effect: 

The small particles of colloidal can easily scatter a beam of visible light, this scattering of a beam of light is called the tyndall effect. 

Cause of tyndall efect: This happens due to the scattering of light by the particles of dust and smoke in the air.

This effect is named 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.
• 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 air.

General examples of colloids that show the tyndall effect: 

Milk, Face cream, fog, clouds, mist, smoke, shaving cream, milk of magnesia, butter, jelly etc.