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INTRODUCTION
Matter is made up of tiny particles called atoms.Individual atoms are extremely small; even the largest atom has an approximate diameter of only 5.4 × 10−10 m. With that size, it takes over 18 million of these atoms, lined up side by side, to equal the width of your little finger (about 1 cm).
Atoms cannot be broken into smaller pieces. All atoms of the same element behave identically chemical ie. they are identical in mass and in all other properties but atoms of different elements differ in mass and other properties.Eg sodium (Na) atom will look different from magnesium(Mg) atom in all its properties .They participate in chemical reactions. During a chemical reaction, atoms are rearranged, but they do not break apart, nor are they created or destroyed
Elements , Compounds And Mixtures
An element is a substance that is composed of only one type of atom, i.e. ,when elements are broken down , they only give several tiny particles of only similar atoms and nothing else. eg if an element containing pure sodium is broken into, will only yield only sodium atoms. There are about 90 naturally occurring elements known on Earth.
Molecules
Most elements in their pure form exist as individual atoms. For example, a macroscopic chunk of iron metal is composed, microscopically, of individual iron atoms. Some elements, however, exist as groups of atoms called molecules.
Several important elements exist as two-atom combinations and are called diatomic molecules.In representing a diatomic molecule, we use the symbol of the element and include the subscript 2 to indicate that two atoms of that element are joined together. The elements that exist as diatomic molecules are hydrogen (H2), oxygen (O2), nitrogen (N2), fluorine (F2), chlorine (Cl2), bromine (Br2), and iodine (I2).
A compound
A compound is a substance made up of several molecules that are chemically combined together .eg water (H2O) is a compound made up as a result of a chemical reaction between Hydrogen(H) and Oxygen (O). This compound cannot be broken down easily by physical means because it is chemically combined and if broken down (by chemical means) it will yield both H and O which are different elements that had been chemically combined together. There are several compounds that exist in nature .
Mixtures
A pure substance consisting of only one compound or of only one form of an element. The compound water with nothing dissolved in it is a pure substance. Air is a mixture of elemental gases and compounds, predominantly nitrogen, oxygen, argon, carbon dioxide, and water vapor.
Drinking water is a mixture containing calcium ion (Ca 2+, hydrogen carbonate ion, (bicarbonate, HCO3–), nitrogen gas, carbon dioxide gas, and other substances dissolved in the water.
Mixtures can be separated into their constituent pure substances by physical processes, for instance ,liquefied air can be distilled to isolate pure oxygen.
There are two types of mixtures
- Homogeneous mixtures are mixtures whose constituents are uniformly mixed throughout ,Homogeneous mixtures are also called solutions, a term that is usually applied to mixtures composed of gases, solids, and other liquids dissolved in a liquid.,
- Heterogeneous mixture is one that is not uniform throughout and possesses readily distinguishable constituents.