Matter is anything that occupies space and has mass. Chemists classify different kinds of matter in a scheme that leads from complex to simpler substances:
Pure Substances:- A pure substance has a definite fixed composition, and any sample will always have the same properties as any other sample when the external conditions (e.g. temperature and pressure) are the same. Pure substances include compounds and elements. A pure substance has a fixed composition as well as a fixed melting point and boiling point.
Every pure substance has some physical and chemical properties. Physical properties can be observed or measured without destroying the basic nature of the substance or changing its composition. When chemical properties are observed or measured, the basic nature of the substance changes.
Elements like silver, gold, copper, and sulfur and compounds like water, salt and sugar are pure substances.
Mixtures:- A mixture is an aggregate of two or more substances that retain their own properties and can be separated by physical means. Many familiar materials are mixtures: air, seawater, milk, steel, wood, marble, and concrete are examples.
Compounds:- Compounds are substances composed of two or more elements chemically united in fixed proportions. A compound is a pure substance that can be decomposed into two or more elements. These elements are present in a fixed proportion in the compound. Oxygen, carbon, hydrogen, nitrogen are elements, and water, carbon dioxide, and ammonia are compounds.
Element:- An element is a substance that cannot be separated into two or more simpler substances by chemical methods. An element cannot be split up into two (or more) simpler substances because it is made of only one kind of atom. For example, copper metal is made of only one kind of atom called 'copper atoms, so copper metal is an element.