Mixture: NCERT Class 9 Chemistry Chapter 2

Mixtures comprise more than one kind of substance. Any physical process cannot be used for the purpose of separating substances into different kinds of matters. Mixtures are available in different kinds and one can differentiate them on the basis of certain physical and chemical properties. This article aims to discuss the topic of mixture. Students can go through this article to understand different types of mixtures and their properties.

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Mixture: Definition

“A mixture is a type of matter formed by mixing two or more pure substances (elements and compounds) in any proportion so that they do not undergo any chemical change and retain their individual properties. Therefore, they are impure substances.”

The majority of the substances we know are in the form of mixtures. Components or constituents of mixtures are the substances that make up a mixture. Air, milk, tap water, honey, ice cream, and other common mixtures are used in our daily lives.

For example, the air is a mixture of gases such as oxygen, nitrogen, argon, carbon dioxide, and water vapour, etc. The various gases in the atmosphere are not chemically combined.

Mixtures: Types

In our daily lives, we come across various types of mixtures. Some of them quite obviously look like mixtures. For example, in a mixture of salt and sugar, or sand and water, the two components are easily distinguished. However, there are some mixtures in which we cannot see the constituents. As an example, consider a sugar solution. In this solution, we cannot see sugar or water separately.

Mixtures: Classification

We have learned that mixtures are formed by the combination of two or more pure substances, such as elements, compounds, or both. There are two types of mixtures. These are homogeneous and heterogeneous.

Homogeneous Mixtures

A mixture is said to be homogeneous if the different constituents or substances present in it are uniformly mixed without any clear boundary of separation.

A homogeneous mixture that has a uniform composition throughout is also known as a solution. A few examples of homogeneous mixtures are as follows:

a. When we dissolve a salt such as sodium chloride or sugar in water, the resulting solution is known as a homogeneous mixture. The constituents are so uniformly mixed that they may be impossible to identify. This means that there is no separation between them.
b. Air is also a homogeneous mixture of various gases such as nitrogen, oxygen, carbon dioxide, water vapours, inert gases, and so on. All of the gases present in the air are uniformly mixed. These gases in the atmosphere cannot be identified.

In a homogeneous mixture, the constituents or components may be present in any proportion. For example, if we make three solutions of copper sulphate in water using different amounts of the crystalline solid, the blue solutions will not have the same intensity of blue. In a homogeneous mixture, the constituents are uniformly mixed and have no boundaries of separation.

The constituent particles of a homogeneous mixture cannot be identified or seen without the use of a powerful microscope.

Heterogeneous Mixtures

A mixture is heterogeneous if it does not have a uniform composition and has visible boundaries of separation between the constituents.

Here are a few examples of heterogeneous mixtures.

1. A heterogeneous mixture is a mixture of sand and common salt. These are, without a doubt, present in the same phase, i.e., solid phase, but have distinct boundaries of separation. The sand and common salt particles are easily visible in the mixture.
2. Similarly, oil and water combine to form a heterogeneous mixture. Both constituents are liquids in this case, but their separation boundaries are different. Oil and water can be found in different layers.

The constituents of a heterogeneous mixture are either present in different phases or in the same phase but with distinct boundaries of separation.

Differences between Homogeneous Mixture and Heterogeneous Mixtures

Following are the differences between homogeneous and heterogeneous mixture

Mixture: Characteristics

1. All mixtures (except solutions) are heterogeneous, which means that their composition is not uniform throughout. As a result, the composition of air containing dust particles and pollutants is a heterogeneous mixture. This is due to the fact that dust particles/pollutants differ depending on the different places.
2. The components of a mixture can be separated using simple techniques such as magnets, decantation, filtration, distillation, sublimation, and so on.

For example, A mixture containing iron powder and sulphur can be separated by using a magnet. When a magnet is placed in this mixture, the iron powder particles are drawn to it and stick to it. In this manner, iron is separated from sulphur.

1. The components of a mixture can exist in any proportion, implying that the composition of a mixture is not fixed. For example, sand and salt can be mixed in various proportions to produce various mixtures.
2. Properties of a mixture are the properties of its constituents. For example, a mixture of iron powder and sulphur possesses both iron and sulphur properties.
3. There is no heat exchange during the formation of a mixture. Between the particles of a heterogeneous mixture, visible separation boundaries can be seen. However, no such boundaries can be seen in a homogeneous mixture.
4. The properties of a heterogeneous mixture do not remain constant throughout the bulk, whereas the properties of a homogeneous mixture do.
5. A mixture does not have a fixed melting and boiling point as it can be made of different compositions.

Difference between Compounds and Mixtures

A mixture is not pure in the sense that it is made up of two or more elements or compounds. To determine whether a sample is a compound or a mixture, we must consider certain characteristics of both.

Summary

A mixture is a type of matter formed by mixing two or more pure substances (elements and compounds) in any proportion so that they do not undergo any chemical change and retain their individual properties. There are two types of mixtures; they are homogeneous mixtures and heterogeneous mixtures.  In this article, we have learnt about the mixture and differences between compounds and mixtures.

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FAQs on Mixture

Frequently asked questions related to mixture is listed as follows:

Q.1. What is a mixture in chemistry?
Ans: “A mixture is a type of matter formed by mixing two or more pure substances (elements and compounds) in any proportion so that they do not undergo any chemical change and retain their individual properties.

Q.2. What are the \(2\) types of mixture?
Ans: The two types of the mixture are;
1. Homogeneous mixture
2. Heterogeneous mixture

Q.3. What is a mixture? Give two examples of the mixture?
Ans: “A mixture is a type of matter formed by mixing two or more pure substances (elements and compounds) in any proportion so that they do not undergo any chemical change and retain their individual properties.
For example, air and a mixture of salt and water.

Q.4. What are \(5\) examples of mixtures?
Ans: Air, milk, tap water, honey and ice cream are five mixtures.

Q.5. What are \(10\) examples of heterogeneous mixtures?
Ans: Ten examples of heterogeneous mixtures are;
1. Sugar and sand mixture
2. Soda with ice
3. Sand and water
4. Oil and water
5. Muddy water
6. Fruit salad
7. The mixture of sulphur and iron filling
8. Orange juice with pulp
9. Milk and cereals
10. Vegetable soup