PARTICULATE NATURE OF MATTER
In our daily life, we come across many objects, the knowledge about which can be gained by one or more of our senses like sight, touch, hearing, taste and smelling. These objects possess mass, occupy space and may have different shapes, sizes and colours. All these objects constitute matter. Matter may thus, be defined as anything that occupies space, possesses mass, offers resistance and can be felt by one or more of our senses. Some examples of matter are, water, air, metals, plants, animals, etc. Thus, matter has countless forms. The matter can be classified into different categories depending upon its physical or chemical nature. Matter is categorized as a gas, a liquid or a solid on the basis of physical state. Air is gas, water is liquid whereas sand is solid. Gases and liquids are fluids but solids are rigid.
On the basis of chemical nature matter is classified as an element, compound or mixture.
Elements and compounds are pure substances whereas mixtures contain two or more pure substances.
In this Unit, we shall study classification of matter on the basis of its physical properties.