With physical properties scientist can tell one matter from another. Chemical properties on the other hand when united with another substance or several other substance it forms another substance. A chemical change takes when two or more substances unite or break apart chemically. Elements are composed of one type of atom. Compounds are composes of different types of atoms linked together. Molecules are several elements that exist naturally. The kind and number of atoms in a molecule determine a molecular mass. A mixture is made of several element or compounds that are physically mixed but aren’t chemically united. There are three types of mixtures but I am only going to talk about two types. One is a solution which is the when molecules of two substances are completely mixed and form a uniform mixture. Most solutions are completely transparent. The next mixture is called a colloid also known as a colloidal dispersion. This happens when a mixture contains tiny clumps or particles that remain suspended within the mixture. Most colloid have a milky appearance under bright lights. This is known as the Tyndall effect. Mostly all chemicals are named for their compounds. There are mainly three formulas to name chemicals. First there is the molecular formula this gives the number of each type of atom in a molecule. This form is efficient but don’t show the arrangement of the various atoms within each molecule. Second there is the structural formula this is the most informative type of chemical formula and shows the general arrangement of the atoms in a molecule. Last is the empirical formula this is the simplest ratio of atoms in a molecule. One empirical formula can often represent dozens of different molecules each having the same type of atoms in the same ratio.

    There are attractive forces that link atoms together called chemical bonds. There are several types of bonds. One is the covalent bond. This is a chemical bond that results from the sharing of valence electrons between atoms. Another is the single covalent bond also called a single bond. This is when two atoms share a single pair of electrons. The next bond is a double bond this happens when two pairs of electrons share. The last bond I will talk about is the triple bond, which is the sharing of three pairs of electrons. A bond can be polar, nonpolar, or dipolar. A polar covalent bond happens when one electron has a stronger electrical attraction for the shared electrons than the other atom(s). A nonpolar covalent bond happens when both atoms have the same strength of electric attraction for the shared electrons. The dipole molecule happens when a molecule has oppositely charged ends or “poles”. Dipole molecules are said to be polar. There is also something called an ionic bond, which is a type of chemical bond in which positively charged ions are electrically attracted to negatively charges ions. Lastly there is something called an ionic crystal. They are mutually attracted ions forming geometric arrangements. The simplest ratio of the ions in the crystal is known as the formula unit.

    There are forces that “glue” objects together called intermolecular forces. Intermolecular forces can be divided into three categories: dipolar forces, London forces, and hydrogen bonds. Dipolar charges are a type of intermolecular force that has attraction between polar molecules. London forces are a type of intermolecular force that occurs between all molecules whether polar or nonpolar. Last is the hydrogen bond, which is unusually a strong intermolecular force present when hydrogen bonds are covalent to certain atoms such as oxygen, nitrogen, or fluorine. Substances arranged in a three-dimensional pattern are known as a crystalline solid each with a repeating unit called a crystal unit. Substances not arranged in a repeating, orderly pattern are classified as amorphous solids. The temperature at which melting occurs is called the melting point. The point at which boiling occurs is called the boiling point. Vapor pressure and boiling point depends on molecular mass and the type of intermolecular forces. The solubility of a substance or the ability of one substance to be dissolved in another substance also creates another substance. In a solution the substance that dissolves is called the solute. The substance into which the solute dissolves is called the solvent. It is said as a rule “like dissolves like” A substance that will not readily dissolve in a given is said to be insoluble.