Chemical Classification of Matter

Suppose you are studying Chemistry for the first time. Or, if you are familiar with the subject, you might be aware that the discipline of Chemistry studies the structure and properties of material substances, that is both physical and chemical classification of matter. For a student of Chemistry, Matter is one of the fundamental areas of the subject. It is an inseparable aspect of Chemistry. We know that the mass of an object is defined as the quantity of Matter contained in it. Mass is a fundamental chemical property of an object that is generally used interchangeably with weight. However, the two are not entirely the same. The mass of an object remains the same irrespective of the location, whereas its weight can differ as per the gravitational force applied to it.

What is Matter?

Matter can often change from one physical state to another in a process called a physical change. For example, liquid water can be heated to form a gas called steam, or steam can be cooled to form liquid water. However, such state changes do not affect the substance’s chemical composition. Matter exists in three states: solids, liquids, and gases in normal conditions. An object is said to be in the solid state if it is relatively rigid and has a fixed shape and volume—for example, ice. Liquids have fixed volumes but no particular shapes. They take the form of the container in which they are placed. For example, water. Gases neither have fixed shapes nor fixed volumes. For example, water vapour. We have provided examples of the different states in which water can exist. When you place water in thezer, it turns to ice. When you boil water, it evaporates in the form of water vapour. Thus, it is clear that Matter can change from one physical state to another. 

If stated in reverse to mass, Matter is something that has mass and occupies space. For instance, people, books, gold, silver, a toffee have mass and are Matter; but energy, light, sound, ideas, feelings and emotion cannot be classified as Matter. A substance is also said to have possessing Matter if it exhibits properties unique to itself, such as smell and colour. For a student of Chemistry, it is crucial to understand what is Matter. Such is its importance in the subject that Chemistry is often known as the study of Matter. Let us know what is it about. 

Chemical Classification of Matter

Figure: Flow chart of chemical classification of matter

As one can notice from the above figure, we can classify Matter in two ways: Pure Substances and Mixtures.

There are very few substances that can be called pure substances. An object is said to be a pure chemical substance if it has a fixed chemical composition and characteristic properties. Oxygen is a pure chemical substance because it is a colourless and odourless gas at 25°C. 

A pure substance can either consist of elements of compounds. An element is the simplest form of a substance that cannot decompose further using chemical changes. For example, metallic sodium. Two or more elements form a compound. This accounts for the reason that the chemical and physical properties of a compound are usually different from the chemical and physical properties of the individual elements of which they are composed. An example of a compound is sodium chloride. Except for a few, usually, all compounds consist of the same elements in the same proportions regardless of their origin. The process that can alter the chemical composition of a substance is called a chemical change. The reaction that accounts for converting two or more elements to a chemical compound, such as converting sodium and chlorine into sodium chloride, is called a chemical reaction. A chemical reaction is an example of a chemical change. We are aware of 118 chemicals present in the periodic table. A million chemical compounds exist today that have been formed from these elements. In reverse, chemical processes break down compounds into their elements. For example, electrolysis breakdown water (a compound) into hydrogen and oxygen (elements). 

More substances that exist around us are mixtures. Mixtures are formed by combining two or more pure substances in variable proportions. In mixtures, the individual substances retain their identity. Some examples of mixtures around us are – air, bread, tap water, dust, etc. Mixtures can be of two types: Homogeneous mixtures and Heterogeneous mixtures. Homogeneous mixtures are formed when matters of all the parts are identical, and all the portions of the material are in the same state and uniform throughout. They are also called solutions. Examples of homogeneous mixtures include tap water and air. 

The components in Homogeneous mixtures or solutions can be separated from one another by physical processes that depend on differences in some physical properties, such as differences in their boiling points. Separating a solution with differences in boiling points is commonly practised if the mixture consists of two or more liquids with differences in boiling points. Such solutions can be separated using a more complex distillation apparatus. 

Distillation and Crystallisation are two standard methods used to separate the components in homogeneous mixtures. If one component of the solution is a liquid, a simple distillation apparatus can separate the mixture of the components. The differences in the volatility of two components separate one component of the solution from another using distillation. For instance, upon the distillation of a salt-water solution, pure water gets collected in the receiving flask while the salt remains in the distillation flask. On the other hand, Crystallisation separates mixtures as per their differences in solubility. At a higher temperature, most substances become soluble. The liquid can be separated from the solution by evaporating it. The least soluble dissolved substances generally form crystals first and can be separated from the solution by filtration.

If the composition in a material is not entirely uniform, it is called a heterogeneous mixture. For example, dust, a chocolate chip cookie. Components in a heterogeneous mixture can be separated using simple means. For instance, one can separate a mixture of sand and water or tea leaves in tea by filtering out the solution. 

Conclusion

To learn further about the concepts related to Chemistry, you can take exams for various grades such as Class 9, Class 10 and higher grades on Embibe. There are various competitive exams, such as NEET and JEE Main, in which examiners ask questions from Chemistry. 

You can learn, practice and give mock tests on Embibe to strengthen your exam preparation. Embibe gives personalised feedback after each test based on your subject knowledge and behavioural aspects of test-taking skills. Learn more at Embibe.