Published by: Nuru
Published date: 16 Jan 2022
A mixture is defined as a mass obtained by mixing up two or more chemically non-reactive substances in any proportion by weight. There are two types of mixture. They are as follows:
1. Homogeneous mixture:
A homogeneous mixture is defined as a mass in which the particles of the components of the mixture are equally distributed. Examples: Sugar solution, air, alcohol water, brass, soda water etc
2. Heterogeneous mixture
A heterogeneous mixture is defined as a mass in which the particles of components of the mixture are not equally distributed. Examples: Smoke, Oily water, Sandy water, etc.
On the basis of the size the particles are divided into following types:
The solution is defined as the homogeneous mixture of two or more than two substances that can be formed either by mixing suitable solid in the liquid or by the liquid in liquid.
Solution = solute + solvent
Solute: It is the component of a solution, which gets dissolved into other substance to form a solution.
Solvent: It is the substance, which dissolves solute to form a solution.
Water: It is a universal solvent that has the capacity of dissolving many substances like common salts, copper sulphate, sugar, etc.
Alcohol: It found in the form of spirit and can dissolve resin and iodine.
Petrol and kerosene: It dissolves ghee, grease, oil, fat, etc and is used for removing clothes stain.
Ether: It is an organic solvent that can dissolve fat, oil, resin, etc.
Colloids
Colloid is a homogeneous mixture in which the diameter of particles of components ranges in between that of particles of a solution and suspension, i.e. a particle’s size ranges from 10-7 cm to 10-5 cm. The colloidal solution of liquid in liquid is called emulsion. Some of the examples of colloids are blood, milk, gum, wax, etc.
Suspensions
The suspension is a heterogeneous mixture in which the diameter of the particle is 10-5 cm or larger. Their particles are visible under a simple microscopic as well as to the naked eyes. Some of the examples of suspensions are sand water, muddy water, smoke in air, etc,
The solution that has relatively a less amount of solute for a given amount of solvent is called dilute solution. The solution that has relatively a large amount of solute for a given amount of solvent is called concentrated solution.
Difference between dilute and concentrated solution
| Dilute solution | Concentrated solution |
| It contains relatively a less amount of solute for a given amount of solvent. | It contains relatively a large amount of solute for a given amount of solvent. |
| Its density is low. | Its density is more. |
| It has less saturation. | It has more saturation. |
Saturated, unsaturated and supersaturated solution
The solution, which can dissolve excess solute at the given temperature, is called unsaturated solution at that temperature. It has less density. Precipitation does not appear on cooling.
The solution, which cannot dissolve excess of the solute at a particular temperature, is called a saturated solution at that temperature. On heating, it becomes unsaturated. Precipitation of solute appears on cooling. It has more density.
The saturated solution at a higher temperature that holds excess solute than the required amount for a saturated solution at that temperature is called supersaturated solution.
Difference between saturated, unsaturated solution, and supersaturated soln
| Unsaturated solution | Saturated solution | Supersaturated solution |
| It can dissolve excess solute at the given temperature. | It cannot dissolve excess of the solute at a particular temperature. | A supersaturated solution is a solution that contains more solute than would dissolve in a saturated solution at a given temperature. |
| On heating, it remains unsaturated. | On heating, it becomes unsaturated. | On heating, it may become saturated |
| Precipitation does not appear on cooling. | Precipitation appears on cooling. | Precipitation occurs when the crystal of a supersaturated solution is dropped. |
| It has less density | It has less density than the supersaturated solution but more than the unsaturated solution. | It has more density. |
Importance of solution are as follows:
The solubility of a substance (solute) at a given temperature is defined as the amount of substance (solute) dissolved in 100 gm. of solvent to make a saturated solution at that temperature.
Mathematically, Solubility (s) ∝ heat energy
Solubility(s)
Effect of heat on Solubility:
The molecules of a solute in solid are compactly packed. But when we heat the solid, they start to vibrate about their mean position as they posses kinectic energy on them. When we increase the temperature their kinetic energy increases and they start to move with high speed. Similary, the molecules of solvent in liquid state are loosely packed as there is less intermolecular force of attraction between them. These molecules of liquid are constantly moving inside. When we heat the liquid, these molecules gain more and more kinectic energy and moves with very high speed.
Also, during shaking , the molecules moves with high speed as they gain kinectic energy during shaking too. As a result the molecules strike with eachother and are separated. This molecules then mixed with the molecules of solvent to make a solution.
More will be the surface area of solute (solid state), more it will mix with molecules of solvent at a faster rate. When we heat the molecules at high temperature, the intermolecular spaces between them increases as the intermolecular force become due to heat. It helps to adjust more molecules of solute in the increased space. So, solubility of the substances also increases with increase in temperature.
Solubility curve
A curve obtained by plotting the solubility of substances at different temperatures against these temperatures is known as solubility curve.
Information obtain from solubility curve are as follows:
Crystals are the granular substances having sharp edges and smooth surface.
Characteristics of crystals
Crystallization
The process in which crystals are formed by cooling a hot saturated solution of solid materials is called crystallization.
To obtain crystals from copper sulphate solution
Take a solution of copper sulphate in a porcelain basin. Make the solution hot saturated either by dissolving more copper sulphate or by evaporating solvent as shown in the figure. Continue heating until the small crystals are seen. Now cool the apparatus. After a while, the crystals are formed. Now, separate the crystals from the mother liquor and place them on filter paper to dry.
Amorphous solids
Those solid substances, which do not have any definite geometrical forms or shapes, are called amorphous solids.
Crystalline solids
Those solid substances, which have definite geometrical forms or shapes, along with definite and rigid morphology, are called crystalline solids.