|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
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
|compound - a grouping of many atoms made up of 2 or more different
types of elements. For example: H2O, C6H12O6,
|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
|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
Chemical equation: H2(g) + O2(g) ------> H2O(g)
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.|