Homogeneous & Heterogeneous Mixture | Definition, Examples

In chemistry, we categorize all materials around us as – pure substances and mixtures. Mixtures are further classified as – homogeneous mixture and heterogeneous mixture. In this post, we will learn about the characteristics of homogeneous and heterogeneous mixtures with examples.

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Mixture Definition

A mixture is an impure substance formed by mixing two or more pure substances (elements and compounds) in any proportion, such that they do not undergo any chemical change and retain their individual property.

Most of the substances known to us are in the form of mixtures. The pure substances which form a mixture are called components or constituents of a mixture. We can form mixtures by mixing elements and compounds or both. A mixture can exist in all three states of matter i.e. solid, liquid, and gaseous state depending on the physical state of its components. As the components of a mixture do not react chemically, therefore we can separate them by various physical methods.

Examples of Mixture

Some common examples of the mixture in our daily life are – air, milk, fruit juice, medicines, honey, tap water, brass, bronze, etc.

Air is a mixture of oxygen, nitrogen, and carbon dioxide gases. It also contains water vapor, dust particles, and traces of inert gases.

Mixtures are of two types – homogeneous and heterogeneous mixture. But before we proceed to study them, let’s learn some basic characteristics of mixtures –

CHARACTERISTICS OF MIXTURES WITH EXAMPLES

In mixtures, components are loosely held together and they retain their individual properties. Based on the same, the mixture exhibits the following characteristics:

• No Physical Change: A mixture consists of two or more pure substances that exist together without any chemical combination between them. For example, in the mixture of common salt and sand, their particles do not bind to each other by any chemical force. We can easily separate common salt by making its solution in water.

• Variable Composition: The components of mixtures vary in their proportions. Therefore, we cannot represent mixtures by any chemical formula. For example, we can prepare a mixture of sand and common salt either by mixing 1 gm of salt with 2 gm of sand, or 2 gm of salt with 2 gm of sand.

• No Specific Physical Properties: A mixture does not have fixed melting and boiling points. It depends upon the proportions of its components present in it. The properties of a mixture are the average of the properties of the components. For example, the boiling point of water depends upon the amount of common salt present in it. The more the amount of a common salt present, the more will be the boiling point of water.

• Homogeneity: A mixture can be homogeneous or heterogeneous. For example, a mixture of common salt and sand is heterogeneous, whereas that of salt and water is homogeneous.

• Separation:  We can separate components of a mixture by simple physical methods. For example, we can separate common salt dissolved in water by the process of evaporation.

• Energy Change: Usually no energy (heat or light) change takes place during the formation of mixtures. For example, when we mix sand with common salt no release or absorption of energy change takes place.

HOMOGENEOUS AND HETEROGENEOUS MIXTURE

Based on their composition and distribution, we can divide mixtures into two types – homogeneous and heterogeneous mixture.

Video courtesy eNotes

HOMOGENEOUS MIXTURE

Definition of the homogeneous mixture–

Homogeneous mixture is the one, in which the components are uniformly distributed throughout its volume and cannot be seen separately.

We should not confuse a homogenous mixture with a compound. In compounds, atoms of various elements combine chemically in a fixed ratio. Whereas, in homogeneous mixtures, components of the mixture stay together in a varying ratio. For more differences between mixture and compound, click here.

Examples of Homogeneous Mixture-

A salt solution in water is an example of a homogeneous mixture as we cannot see salt particles separately from water. We can prepare a salt solution by mixing one or two tablespoons in 1 liter of water. In both cases, the solution formed will be homogeneous, but the proportions of salt and water are not the same.

Some other examples of the homogeneous mixture are – tap water,  milk, air, fruit juice, medicine, etc.

We can form a homogeneous mixture of metals by mixing two or more metals in the molten state. This homogeneous mixture of molten metals on cooling forms a solid mixture. We call this solid mixture an alloy. For example, brass is an alloy of copper and zinc. Similarly, bronze is an alloy of copper, zinc, and tin.

HETEROGENEOUS MIXTURE

Definition of the heterogeneous mixture-

Heterogeneous mixture is the one, in which the components are not uniformly distributed throughout its volume and can be easily seen separately.

We can easily identify various components of a heterogeneous mixture with the naked eye or under a microscope.

Examples of the heterogeneous mixture –

Most of the mixtures occurring in nature are heterogeneous. For example, the soil is a mixture of hundreds of elements and compounds. Its composition changes from place to place. Some other examples of the heterogeneous mixture are – rocks, a mixture of kerosene and water, rice and pulses, etc.

EXAMPLES OF MIXTURES AND THEIR TYPES