Review Definitions
States of matter: 3 common states - solid, liquid and gas
                            4th uncommon state - plasma
 
Changes of state: - 6 common ones
 
Condition: Heat is added       solid ---> gas      sublimation (s->g)
                                               solid ---> liquid    melting
                                               liquid --> gas       boiling
 
                Heat is removed:   gas ---> solid      sublimation (g->s)
                                             liquid --> solid      freezing
                                               gas ---> liquid     condensing
 
homogeneous - when there is only 1 visible phase that can be seen with the naked eye. eg. milk, water solutions
 
heterogeneous - when there is more than 1 visible phase eg. sand and water, oil and water, granite rock.
 
mechanical mixture - usually used to describe a mixture of ingredients which after mixing still is heterogeneous.
 
solution - used to describe a homogeneous mixture of either 2 gases, 2 liquids or a gas in a liquid or a liquid in a liquid in which the solute disappears completely in the liquid (solvent) phase. A liquid which can dissolve in a solvent is said to be miscible. A solid which can dissolve in a solvent is said to be soluble.
 
solute - the substance that gets dissolved.
 
solvent - the substance that does the dissolving.
 
pure substance - an element or compound that is uncontaminated.
 
element - there are 104 known eleemnts, 80 of these are found naturally.  These range from Hydrogen (H) to Seaborgium (Sg). These 104 elements are the building blocks of all other substances in the universe. Usually they are written as single atoms. For example: Fe, Al, Co, Ni, W. There are exceptions in which some elements are always found combined with others of their kind. For example: H2, F2, Cl2, P4 and S8. Even though they are not single atoms anymore, since they are made from only one type of atom then they are still considered to be elements.
 
compound - a grouping of many atoms made up of 2 or more different types of elements. For example: H2O,    C6H12O6,   C6H5(NO2)3
 
physical change - a change of state only. The substance stays essentially the same but in a different form. eg. grinding bluestone or breaking glass.
 
chemical change - when a compound rearranges the elements in itself or with those of another compound to create a new compound which was not present before.
 
chemical reactions - All reactions are written such that the substances that get changed are written on the left. These are the reactants. All new substances created are written on the right and are called products. The arrow symbol means react to become. Thus
        reactants react to become products
    Word equation:   hydrogen gas and oxygen gas -------> water

     Chemical equation:  H2(g) + O2(g) ------> H2O(g)

A chemical equation describes what happens when a chemical reaction occurs. It uses chemical formulas to provide us with a before and after picture of the chemical substances involved.

example:    Zn + S8 -----> ZnS  (elemental zinc and elemental sulphur react to form zinc chloride).
 

Physical and Chemical Properties
Physical properties are characteristics that can be specified with reference to other substances. Examples of physical properties are state, mass, volume. Mass and volume are extensive properties because they depend upon the amount of substance you are observing at that time. Extensive properties are not particularly useful when trying to identify a substance. There are intensive properties which do not depend upon the size of the sample of substance you are observing. For example, melting point and boiling point, colour, electrical conductance, or the ability to be magnetized are intensive properties. For example all samples of copper metal (Cu), no matter what the size of the sample, will melt at the same temperature, are reddish in colour when polished, and are good electrical conductors.
 
A chemical property of a substance is any chemcial reaction that the substance can undergo. Iron when exposed to oxygen will rust. The ability of iron to combine with oxygen to form rust is a chemical property of iron, and also of oxygen. We could use this property to distinguish between a sample of Fe and a sample of gold (Au) which does not rust appreciably in oxygen. When we observe a chemical property, the substance usually changes to something else with a different composition and its own unique set of physical properties. When we observe a physical property no alteration occurs.