Definition of Mixture: In chemistry, a mixture is a substance that contains two or more substances, either elements or compounds or both in any ratio.
In other words, a mixture is a material that contains particles of two or more pure substances in any proportion. It is formed when elements or compound or both mix together and no new compound is formed. In simple words, a mixture means a combination of different things or substances.
Mixtures can contain various types of particles or substances. Hence, their composition is variable.
When all constituent particles of a substance are same in chemical nature (i.e. have the same chemical properties), it is a pure substance.
Pure substances which forms a mixture are called its components or constituents. In the mixture, components are present without loss of their identity (i.e. chemical properties).
Many of the substances present around us are mixtures. For example, air, salt in water, sugar solution in water, tea, your pencil (a mixture of wood and lead), etc. are all mixtures.
Properties of Mixtures in Chemistry
The constituent elements of a mixture are not present in a certain proportion or ratio. There are the following various properties of mixtures that you should keep them in mind.
- No chemical force acts between the two or more substances (i.e. elements or compounds) that are mixed, but they still stay on together.
- Mixtures can be homogeneous or heterogeneous in nature.
- The proportions of the components may vary in an indefinite manner.
- The properties of the mixtures depend upon the individual constituents.
- Physical methods can separate the constituents of the mixture.
- The boiling point and the melting point of the mixtures depend upon the properties of the constituents. They are not fixed.
- No chemical change occurs during the formation of mixtures.
- Mixtures can form from all states of matter, such as solid, liquid, and gases.
Types of Mixtures in Chemistry
Depending upon the nature of the components, there are two types of mixtures in chemistry. They are:
- Homogeneous
- Heterogeneous
Let’s understand each with the help of examples.
What is a Homogeneous Mixture?
A homogeneous mixture is a mixture that has the uniform composition throughout. It contains only one phase. A phase is a part of a system which has the same properties and composition. Homo means same.
In a homogeneous mixture, the components completely mix with each other to microscopic level. It means particles of components of the mixture uniformly distributed throughout the mixture and its properties and composition are the same throughout. Such a mixture is isotropic in nature. This means that every portion of it has the same properties and composition.
Air, sugar dissolved in water, common salt dissolved in water, iodine dissolved in carbon tetrachloride, benzene in toluene, methyl alcohol in water, gasoline (a mixture of hydrocarbons), copper sulphate solution, etc. are some examples of homogeneous mixtures. Look at the below figure of a homogeneous mixture of sugar and water.
Fig
A mixture or solution of sugar and water is a single phase system. Every drop of the solution has the same properties and uniform composition. That is, the taste of the sugar solution will be the same if we take a sip from any portion of water. This shows that sugar is uniformly distributed in the mixture or solution.
Homogeneous mixtures may contain two or more components. Therefore, the composition of such mixtures is variable. For example, we can add different amount of sugar in the same quantity of water. We cannot see the components of a homogeneous mixture with the naked eye or with the help of a microscope.
Properties of Homogeneous mixtures
The key properties of homogeneous mixtures are as:
- Particles of components uniformly distributed throughout the mixture. We cannot separate the boundaries of particles.
- Homogeneous mixtures show isotropic nature, meaning every portion of it has the same properties and composition.
- We cannot use the centrifugal force to separate the components.
- Homogeneous mixtures do not show the Tyndall effect.
- The particle size in such a mixture is less than 1 nm.
- All the solutions are the example of homogeneous mixtures.
Classification of Homogeneous Mixtures
We can further classify homogeneous mixtures as follows:
(a) Solid-solid mixtures: Examples of such mixtures are bronze, brass, 22-carat gold, steel, etc. They are alloys. An alloy is a homogeneous mixture of two or more metals (or non-metals). We use it in the construction and other various types of industries.
(b) Solid-liquid mixtures: Examples of such mixtures are an aqueous solution of salt or sugar, solution of iodine (I2) and carbon tetra chloride (CCl4), etc.
(c) Liquid-liquid mixtures: Examples of this type of mixtures are a mixture of alcohol and water, a mixture of toluene and benzene, etc.
What is a Heterogeneous Mixture?
A heterogeneous mixture is a nonuniform mixture in which the composition is not uniform throughout. It can have two or more phases with definite boundaries between the phases. Hetero means different.
In a heterogeneous mixture, the properties and composition are not uniform throughout the mixture. That is, the particles of each component of the mixture remain separate and can be seen by the naked eye or with the help of a microscope.
For example, mixtures of salt and sugar, or grains and pulses, along with some dirt (often sand) show the heterogeneous mixtures.
Another familiar example of heterogeneous mixtures are a mixture of oil and water. Oil and mixture forms a heterogeneous mixture because we can’t mix them. Look at the below figure to understand it better.
Fig:
Some other examples of heterogeneous mixtures are a mixture of sodium chloride and iron filings, a mixture of salt and sulphur, smoke, etc. You can think of many more examples of homogeneous and heterogeneous mixtures which you come across in the everyday life.
Properties of Heterogeneous Mixtures
There are the following key properties of heterogeneous mixtures. They are:
- The properties and composition of heterogeneous mixture do not uniform throughout the mixture.
- Each component of the mixture remains separate, with definite boundaries.
- The particle size in such a mixture ranges between 1nm to 1μm.
- Heterogeneous mixtures can exhibit the Tyndall effect.
Classification of Heterogeneous Mixtures
(a) Solid-solid mixtures: Examples of such mixtures are gun powder, a mixture of sulphur and iron filings.
(b) Solid-liquid mixtures: An example of it is a suspension of sulphur in water.
(c) Solid-gas mixtures: Am example of it is hydrogen gas absorbed on palladium.
(d) Liquid-liquid mixtures: Milk, Benzene in water.
Difference between Mixtures and Compounds
| Mixtures | Compounds |
|---|---|
| With the help of physical processes, such as filtration, evaporation, sublimation, and distillation, we can separate a mixture into its constituents. | With the help of physical processes, we cannot separate a compound into its constituents. We can separate it by chemical reaction. |
| A mixture shows the properties of its constituents. | A compound shows a new set of properties different from its constituents. |
| The composition of a mixture is variable, and the constituents may be present in any ratio by weight. It has not a definite formula. | The composition of a compound is fixed and the constituents are present in a definite ratio by weight. It has a fixed formula. |
| No energy change occurs because constituents do not react chemically. | Energy change occurs in the form of heat and light when a chemical reaction occurs. |
| A mixture does not have a fixed melting point and boiling point. Example: air, salt, and sand. | A compound has a definite melting point and boiling point. Example: water, iron sulphide (FeS). |
Difference between Homogeneous and Heterogeneous Mixtures
| Homogeneous | Heterogeneous |
|---|---|
| A homogeneous mixture contains the same composition throughout. | A heterogeneous mixture contains different composition in different paths. |
| We cannot see the components of such a mixture with the naked eyes or even under a microscope. | We can see the components of such a mixture with the naked eyes. |
Frequently Asked Questions on Mixtures in Chemistry
Q. What is a mixture in chemistry?
In chemistry, a mixture is a combination of two or more substance (i.e. elements or compounds) in any arbitrary ratio and is not chemically combined with each other.
Q. What are the three main properties of mixtures?
The three main properties of mixtures are as follows:
1. Each component of a mixture keep their original physical and essential chemical properties with no changes.
2. With the help of a simple mechanical blending process, the separation of components can be easily done.
3. The components of a mixture may be present at any ratio.
4. The constituent elements do not form any new chemical bond while in a mixture.
Q. What are the familiar examples of mixtures in our daily life?
The familiar examples of mixtures in our daily life are as:
a) Cement that is a mixture of water, sand and gravel.
b) Sea water, which is a mixture of water and salt.
c) Soil is a mixture of minerals, organic materials, water, and living organisms.
d) Blood is a mixture of plasma, red blood cells, white blood cells, and platelets.
e) Smog (a mixture of smoke and fog).
f) Bleach (a mixture of caustic soda, chlorine, and water).
Q. Is water a mixture or compound?
Water is a compound, not a mixture.
Q. Classify the following substances into elements, compounds, and mixtures.
Milk, Vinegar, 22-carat gold, Iodized table salt, Hydrogen, Oxygen, Carbon, Diamond, German silver, Smoke, Air, Steel, Dry ice, Brass, Mercury, Glucose, Petrol/Diesel/Kerosene oil, Steam, Cloud, Sodium sulphate, Salt solution, Sulphuric acid, Hydrochloric acid, Ammonia.
Elements: Hydrogen, Oxygen, Carbon, Diamond, Mercury.
Compounds: Dry ice, Glucose, Steam, Cloud, Sodium sulphate, Sulphuric acid, Hydrochloric acid, Ammonia.
Mixtures: Milk, Vinegar, 22-carat gold, iodized table salt, German silver, Smoke, Air, Steel, Brass, Petrol/Diesel/Kerosene oil, Salt solution.
Q. Classify the following substances into homogeneous or heterogeneous mixtures.
Milk, 22-carat gold, iodized table salt, Vinegar, German silver, Smoke, Air, Steel, Brass, Petrol/Diesel/Kerosene oil, Salt solution.
Homogeneous mixtures: Air, 22-carat gold, Vinegar, German silver, Steel, Brass, Petrol/Diesel/Kerosene oil, Salt solution.
Heterogeneous mixtures: Milk, Iodized table salt, Smoke.
In this tutorial, you have known about what is a mixture in chemistry and its various properties. Hope that you have understood the basic points of homogeneous and heterogeneous mixtures with a lot of different examples.
Thanks for reading!!!
