Chemistry GCSE unit 1 principle of chemistry

       Melting        Bioling 
       ------->        -------->
Solid         Liquid         Gas
       <-------        <--------
       Freezing     Condensing

Solids= Molecules are tightly packed and held in postitions by strong forces. The molecules vibrate around their fixed positions. As the solid gets hotter, these vibrations get bigger.

Liquids= Molecules are closely packed but do not have a regular structure. The forces between the molecules are strong. The molecules move randomly.

Gas= Molecules are widely spaced and in a continous state of motion. The forces are very small except during collisions. The molecules move randomly. 

Atom= is the particle made up of a nucleus containing protons + Neutrons surrounded by electrons.

Molecule= is two or more atoms which are chemically bonded together.

Elements= is a simple substance which cannot be split up into simpler subtances.

Compound= is two elements chemically combimed. E.g iron sulphide.

Mixture= consits of 2 or more different elements and/ or compounds together these are not chemically combined. 

Solutions 
Solvite= substance which is dissolved in a solvent to make an solution.|
Solvent= liquid that does the dissolving 
Solution= a solution is the result of a solute dissolved solvent
A solution is always clear but not necesserly colourless.

Solute + Solvent = Solution

Crystallisation=  a solute crystallises out of a saturated solution. If a solution is unsaturated some of the solvent must be evaporated before crystals formed.

Filtration= Used to seperate a sold and liquid. E.g for making pure drinking water.

Distillation= When seperating a solvent from a solution. E.g when drinking water is obtained from sea water.
Vaporisation ---> Condensation= Distillation

 Fractional Distillation= The seperation of a mixture into its components parts, or fractions, such as seperating chemical compounds by their bioling point. by heating them to a temperature at which several fractions of the compound will evaporate.

              Mass           Charge

Proton      1                  +

Neutron    1                  0

electron    0.005           -

Protons + Neutrons = Mass number 

Number of protons is called atomic number.

Number of neutrons =  mass number / atomic number

Relative atomic mass = mass of one atom of the element / mass of one atom of hydrogen 

All atoms of the same element all contain the same number number of protons, but the number of neutrons maybe different. Forms of an element which differ in the number of neutrons in the atom are called isotopes. 

·         Elements in the Periodic table are listed in order of increasing atomic number.

·         The vertical columns are called ‘Groups’. Elements with the same number of electrons in the outer most shell fall into the same group.
·         Noble gases are in group 0
·         Horizontal rows are called ‘Periods

Chemical properties of Metallic and non-metallic Elements

Metallic Compounds

Non-Metallic Compounds

Metals which are high in the reactivity series react with dilute acids o give hydrogen and salt of the metal

Do not react with dilute acid

Form positive ions

Form negative ions

Many metal oxides and hydroxides are bases . if they dissolve in water they give alkaline solution.

The chloride of metals are ionic crystalline solids. E.G. Sodium Hydroxide

Many oxides are acids and dissolve in water to give a acidic solution. Some oxides are neutral and others are insoluble.

The chlorides of the non-metals are covalent liquid or gasses

Nobles gasses are unreactive because they have a full outer shell.