Classification Of Matter

Introduction

What is your body made of? Your first thought might be that it is made up of different organs—such as your heart, lungs, and stomach—that work together to keep your body going. Or you might zoom in a level and say that your body is made up of many different types of cells. However, at the most basic level, your body—and, in fact, all of life, as well as the nonliving world—is made up of atoms, often organized into larger structures called molecules.

1. Atoms

An atom is the smallest constituent unit of ordinary matter that has the properties of a chemical element. Every solid, liquid, gas, and plasma is composed of neutral or ionized atoms. Atoms are very small; typical sizes are around 100 picometers (a ten-billionth of a meter, in the short scale).
Atoms are small enough that attempting to predict their behavior using classical physics - as if they were billiard balls, for example - gives noticeably incorrect predictions due to quantum effects. Through the development of physics, atomic models have incorporated quantum principles to better explain and predict the behavior.
Every atom is composed of a nucleus and one or more electrons bound to the nucleus. The nucleus is made of one or more protons and typically a similar number of neutrons. Protons and neutrons are called nucleons. More than 99.94% of an atom's mass is in the nucleus. The protons have a positive electric charge, the electrons have a negative electric charge, and the neutrons have no electric charge. If the number of protons and electrons are equal, that atom is electrically neutral. If an atom has more or fewer electrons than protons, then it has an overall negative or positive charge, respectively, and it is called an ion.
The electrons of an atom are attracted to the protons in an atomic nucleus by this electromagnetic force. The protons and neutrons in the nucleus are attracted to each other by a different force, the nuclear force, which is usually stronger than the electromagnetic force repelling the positively charged protons from one another. Under certain circumstances the repelling electromagnetic force becomes stronger than the nuclear force, and nucleons can be ejected from the nucleus, leaving behind a different element: nuclear decay resulting in nuclear transmutation.
The number of protons in the nucleus defines to what chemical element the atom belongs: for example, all copper atoms contain 29 protons. The number of neutrons defines the isotope of the element. The number of electrons influences the magnetic properties of an atom. Atoms can attach to one or more other atoms by chemical bonds to form chemical compounds such as molecules. The ability of atoms to associate and dissociate is responsible for most of the physical changes observed in nature, and is the subject of the discipline of chemistry.

2. Element

Elements are pure substances that are composed of identical atoms with the same atomic number. The elements cannot be decomposed into simpler substances by physical nor chemical methods. For example, calcium and bromine are examples of elements. All known natural and synthesized elements can be found on the periodic table.



Compounds are pure substances composed of two or more different elements that are chemically combined. Properties and composition of a compound are definite in all samples of the compound.Properties of a compound are always different from those of the elements found in the compound.

3. Molecule

A molecule is an electrically neutral group of two or more atoms held together by chemical bonds. Molecules are distinguished from ions by their lack of electrical charge. However, in quantum physics, organic chemistry, and biochemistry, the term molecule is often used less strictly, also being applied to polyatomic ions.
In the kinetic theory of gases, the term molecule is often used for any gaseous particle regardless of its composition. According to this definition, noble gas atoms are considered molecules as they are in fact monoatomic molecules.
A molecule may be homonuclear, that is, it consists of atoms of one chemical element, as with oxygen (O₂); or it may be heteronuclear, a chemical compound composed of more than one element, as with water (H₂O). Atoms and complexes connected by non-covalent interactions, such as hydrogen bonds or ionic bonds, are generally not considered single molecules.
Molecules as components of matter are common in organic substances (and therefore biochemistry). They also make up most of the oceans and atmosphere. However, the majority of familiar solid substances on Earth, including most of the minerals that make up the crust, mantle, and core of the Earth, contain many chemical bonds, but are not made of identifiable molecules. Also, no typical molecule can be defined for ionic crystals (salts) and covalent crystals (network solids), although these are often composed of repeating unit cells that extend either in a plane (such as in graphene) or three-dimensionally (such as in diamond, quartz, or sodium chloride). The theme of repeated unit-cellular-structure also holds for most condensed phases with metallic bonding, which means that solid metals are also not made of molecules. In glasses (solids that exist in a vitreous disordered state), atoms may also be held together by chemical bonds with no presence of any definable molecule, nor any of the regularity of repeating units that characterizes crystals.

 4. Compound

a compound is a substance that results from a combination of two or more different chemical element s, in such a way that the atom s of the different elements are held together by chemical bonds that are difficult to break. These bonds form as a result of the sharing or exchange of electron s among the atoms. The smallest unbreakable unit of a compound is called a molecule .

A compound differs from a mixture, in which bonding among the atoms of the constituent substances does not occur. In some situations, different elements react with each other when they are mixed, forming bonds among the atoms and thereby producing molecules of a compound. In other scenarios, different elements can be mixed and no reaction occurs, so the elements retain their individual identities. Sometimes, when elements are mixed, the reaction occurs slowly (as when iron is exposed to oxygen); in other cases it takes place rapidly (as when lithium is exposed to oxygen). Sometimes, when an element is exposed to a compound, a reaction occurs in which new compounds are formed (as when pure elemental sodium is immersed in liquid water).

5. Mixtures 

Mixtures are formed by just mixing or "intermingling" (another word which means the same as "mixing") together two or more substances. Those substances may also be referred to as "constituents" or "components" - and may be either elements or compounds, and be composed of either atoms or molecules. There are no chemical reactions between the constituents of mixtures, which can therefore also be seperated without any chemical reactions taking place.

List of facts about Mixtures:

1. Mixtures consist of two or more different elements and/or compounds - physically intermingled, so
2. Mixtures can include:
• at least two different types of atoms, or
• at least two different types of molecules, or
• at least one type of atom and at least one type of molecule.
3. Mixtures can be formed from the intermingling of their constituents in any ratios or proportions (unlike compounds, which are formed from specific ratios of amounts of other elements).
4. Mixtures can be separated into their constituents by physical means.
5. Mixtures have many of the properties of their constituents (e.g. the element "oxygen" is part of the mixture "air" and some of the properties of air are due to the oxygen part - but those properties are generally less strong/intense than those of pure oxygen because of the presence of the other constituents of the mixture called "air", e.g. many substances, such as wood, burn in air and burn even more vigourously in pure oxygen).
6. Mixtures do not have fixed precise melting and boiling points (which elements and compounds do have), but instead mixtures melt/freeze and boil/condense over a range of temperatures according to the physical properties of the different constituents of the mixture.
7. Because no chemical reaction takes place when a mixture is formed, no energy (e.g. heat, light or electrical energy) is released or absorbed during the formation of a mixture.

Do mixtures consist of atoms or molecules ?

Mixtures can consist of either atoms or molecules - but must include at least two different atoms or molecules.