You can see many things around you. Dining table, chair, rice, wheat inside your home, soil, trees, plants outside the home,  blackboard, chalk piece at your school and the list is endless. Have you ever wondered what is it all made up of?

The answer is matter. Anything and everything in this universe is made up of matter.

A substance is a matter with clearly defined properties and constitution. Every pure element and compound is a substance.

Iron and Methane are examples of substances.

Two or more substances form a mixture.

Lime juice is an example of a mixture of sugar, lime drops and water.

In this chapter, you will learn more about substance, mixture, difference between substances and mixtures and a diagrammatic representation showing the classification of matter into substances and mixture.

Substances

1. Pure substances find uses in several industries. They can be used in medicines, chemicals, scientific research and experiments.
2. Substances may be separated from mixtures.
3. All solutions are mixtures but all mixtures are not solutions.

Mixtures

• Matter generally exists as mixtures of two or more pure components or substances
• Characteristics of a mixture:
  • Elements and compounds just mix to form a mixture, no chemical reaction.
  • Composition variable.
  • Retains properties of constituents, which can be separated by physical means.
  • Mixtures may be homogeneous or heterogeneous.

Differences between substances and mixtures

Properties	Pure substances	Mixtures
Made of	Atoms or molecules.	Made of elements or compounds or both.
Composition	Compounds have fixed composition. The elements are always present in a definite proportion. E.g. sodium chloride will always contain one atom of sodium chemically bound to one atom of chlorine irrespective of its source.	A mixture does not have a definite composition. The percentage of each substance in a mixture can vary.
Physical properties	Fixed boiling and melting points.	No definite properties. Boiling point and melting point will depend on the amounts of the constituents present in the mixture.
Chemical properties	Properties of compounds are different from the properties of its constituent elements. E.g. Water is a liquid while hydrogen and oxygen are gases.	Components are loosely held together and they retain their individual properties
Formation	Formation of a compound is accompanied by energy change in the form of heat, light, sound or colour.	Formation of the mixture does not involve any energy change.
Separation	Cannot be broken down into constituents by physical means. Chemical processes are needed.	Can be easily separated into its components by physical means.
Appearance	Characteristic taste, smell, odour.	Take the appearance of the components.
Uniformity	Always homogeneous.	Can be homogeneous or heterogeneous.
Examples	lead, gold, silver, aluminium (elements).carbon dioxide, ammonia, water, calcium carbonate (compounds).	Salt solution, sugar solution, alloys like bronze and brass, milk, air, honey (homogeneous mixtures.Chalk in water, dust in air, sulphur and iron filings, soil (heterogeneous mixture).