What are the three classification of matter?

Matter and its classifications:

Matter is anything that has mass and occupies space. It can be classified either with respect to its physical phases or with respect to its composition.

The three phases of matter are solid, liquid, and gas. A solid has a fixed shape and volume. A liquid has a fixed volume but is not rigid in shape; it takes the shape of its container. A gas has neither a fixed volume nor a shape. It takes on both the shape and the volume of its container.

Matter can also be classified with respect to its composition:

• pure substances, each of which has a fixed composition and a unique set of properties.

• mixtures, composed of two or more substances.

Pure substances are either elements or compounds, whereas mixtures can be either homogeneous or heterogeneous.

1- Elements

An element is a type of matter that cannot be broken down into two or more pure substances. There are 118 known elements, of which 91 occur naturally.

Many elements are familiar to all of us. The charcoal used in outdoor grills is nearly pure carbon. Electrical wiring, jewellery, and water pipes are often made from copper, a metallic element. Another such element, aluminum, is used in many household utensils.

In chemistry, an element is identified by its symbol. This consists of one or two letters, usually derived from the name of the element. Thus the symbol for carbon is C; that for aluminum is Al. Sometimes the symbol comes from the Latin name of the element or one of its compounds. The two elements copper and mercury, which were known in ancient times, have the symbols Cu (cuprum) and Hg (hydrargyrum).

2- Compounds:

A compound is a pure substance that contains more than one element. Water is a compound of hydrogen and oxygen. The compounds methane, acetylene, and naphthalene all contain the elements carbon and hydrogen, in different proportions.

Compounds have fixed compositions. That is, a given compound always contains the same elements in the same percentages by mass. A sample of pure water contains precisely 11.19% hydrogen and 88.81% oxygen. In contrast, mixtures can vary in composition. For example, a mixture of hydrogen and oxygen might contain 5, 10, 25, or 60% hydrogen, along with 95, 90, 75, or 40% oxygen.

The properties of compounds are usually very different from those of the elements they contain. Ordinary table salt, sodium chloride, is a white, un-reactive solid. As you can guess from its name, it contains the two elements sodium and chlorine. Sodium (Na) is a shiny, extremely reactive metal. Chlorine (Cl) is a poisonous, greenish-yellow gas. Clearly, when these two elements combine to form sodium chloride, a profound change takes place.

Many different methods can be used to resolve compounds into their elements. Sometimes, but not often, heat alone is sufficient. Mercury(II) oxide, a compound of mercury and oxygen, decomposes to its elements when heated to 600°C. Another method of resolving compounds into elements is electrolysis, which involves passing an electric current through a compound, usually in the liquid state. By electrolysis it is possible to separate water into the gaseous elements hydrogen and oxygen.

3-Mixture:

A mixture contains two or more substances combined in such a way that each substance retains its chemical identity. When you shake copper sulfate with sand, the two substances do not react with one another. In contrast, when sodium is exposed to chlorine gas, a new compound, sodium chloride, is formed.