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Chemistry – Form iii
Atomic Structure
States of matter:
Solids | Liquids | Gases |
* Definite shape. * Definite volume. * Particles close together. * Pure kinetic energy (vibrate). * Can’t be compressed. | * Indefinite shape. * Definite volume. * Take the shape of the container. * Particles are close together but mobile. * Particles move slowly. * Can’t becompressed. | * Indefinite shape. * Indefinite volume. * Take the shape and volume of container. * Particles are far apart. * Particles move fast. |

Changes of state:


* Melting: is the process in which a substance changes from a solid to liquid.
* Freezing: is the process inwhich a substance changes from liquid to solid.
* Evaporation: is the process in which a substance changes from a liquid to gas.
* Condensation: is the process in which a substance changes from gas to liquid.
* Deposition: is the process in which a substance changes from gas to solid.
* Direct sublimation: is the process in which a substance from solid directly to gas.
*Sublimation: is the whole process in which a substance goes through solid, liquid and gas states.
Elements and the atom:
There are currently 118 elements that have been indentified though only 88 of them are naturally occurring.
ELEMENTS are pure substances; this means that even if you break it into a million pieces it will still have the same properties and materials. They don’t lose theiridentity if they are broken down.
The chemical symbols are shorthand ways of representing the elements, they usually have 1 or 2 letters and they are taken from the name of the element. Some come from their Latin name. For example:
* Gold = Au : Aurum
* Silver = Ag : Argentum
* Iron = Fe : Ferrum

Atomic structure:
* The smallest of the element is anATOM.
* They are made of 3 sub-atomic particles: Protons, Neustrons and electrons.
* Protons present positive (+) charge.
* Neutrons don’t have charge.
* Electrons present negative (-) charge.

Particle | Symbol | Charge | Relativemass |
Electron | e- | - | 0 |
Proton | p+ | + | 1 |
Neutron | n | 0 | 1 |

The atomic number and the mass number:
* The atomic number (Z): number of protons in the atom.
* Mass number or nuclear number (A): number of protons plus number of neutrons in the atom.
* Isotopes: are different types of atoms of the samechemical element, each having a different number of neutrons.
* Differ in mass number (or number of nucleons) but not in atomic number.
Compound and mixtures and molecules:
* MIXTURE: contains 2 or more types of atom or compound NOT chemically joined.
* COMPUOND: pure substances made up of more than one element.
* MOLECULE: is an aggregate of two or more atoms in adefinite arrangement held together by chemical bonds.
There are different methods to separate: mixtures, like:
* Filtration: separate a solid from a liquid
* Evaporation: to obtain the solute of a solution.
* Simple distillation: to obtain a solvent (e.g. water) from a solution.
* Fractional distillation: to separate one liquid from a mixture that has differentboiling points.
* Chromatography: to separate one color from the other.
* Compound made of oxygen and oxides and the increase in mass is due to the oxygen.
The periodic Table:
The periodic table:
* The elements in the Periodic Table are arranged in order of proton number.
* The vertical columns are called GROUPS.
* The horizontal lines are called PERIODS.
* The group...
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