Class 9 Science Note


mixture is a made up of two or more different substances which are mixed but are not chemically combined. A mixture refers to the physical combination of two or more substances on which the identities are retained and are mixed in the form of solutions, suspensions, and colloids.


Heterogeneous mixture:

A mixture which can be seen through our naked eyes is called heterogeneous mixture. E.g. mixture of sand and rice


Homogeneous mixture

A mixture which can be seen through our naked eyes is called homogeneous mixture. E.g. sugar solution.


According to the particle size mixture can be categorized into three types


Solution: Homogeneous mixture of two or more substances is called solution.Example: Salt and water etc. The substance which is dissolved is called solute and the substance that dissolves is called solvent.

Solution= solvent + solute


Colloids: If the diameter of the particle of a substance in a solvent is 10-5 to 10-7 then the mixture is called colloidal. Particle size in colloidal solution is intermediate between solution and suspension.

Example: blood, milk

Suspension: It is the heterogeneous mixture of solid and liquid particles in which particle size is 10-5 or bigger. E.g. smoke particles in air.





Saturated solution

The solution in which the solvent cannot dissolve the solute anymore, at the given temperature then it is known as saturated solution at that temperature. When we dissolve solute in a solvent and there comes a time when the solute won't get dissolved anymore, then this solution is considered as saturated solution.


Example: When we pour sugar in the water and stir it, the sugar keeps dissolving but on further dissolving the sugar, a state will come when the sugar will not get dissolved in the water. At this point, the solution is a saturated solution.


Unsaturated solution

A solution at a state before saturation in called an unsaturated solution. In other words, the solution which can dissolve the solute at the given temperature is known as unsaturated solution at that temperature.


Solutions having low concentration of solute particles are called dilute solution.

Solutions having high concentration of solute particles are called concentrated solution.


Solubility of the substance

The amount of solute required to form a solution in 100 gm of solvent at a particular temperature to give saturated solution is the solubility of that solute at that temperature.

The solubility of a substance at certain temperature can be given by

Solubility =  * 100



Effect of the temperature on solubility

The relationship between increase in temperature and solubility is that the  the solubility is directly proportional to the increase in the temperature.i.e. At high temperature the solubility of a solution is high so it is able to dissolve more solute, but when it is cooled, the solubility of the solution decreases and due to which the solute separate out as solid.




Solubility curve

Solubility curve is curve obtained by the plotting the solubility of the substance at different temperature against these temperatures.


 From the solubility curve various information can be obtained which are listed below

I. Comparative study of the solubility of different solutes can be done.

II .The solubility of solute at any temperature can be found out.

III. The change in solubility on changes in temperature can be observed.




 A solid which has certain geometrical shape and certain boiling and freezing point is called crystal. It is formed by the process of crystallization. 



When the saturated mixture of a solid in a liquid at a high temperature is allowed to cool down, solid deposits in a certain geometrical shape called crystal .The process of separating such mixture is called crystallization.

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