Atoms/ Elements and compounds

Atom- smallest part of an element that can exist (all substances are made of atoms)

Element- substance that contains only 1 type of atom. The atoms of each elements are shown by a different symbol e.g sodium = Na carbon =C

Compound- a compound contains atoms of 2 or more elements, which are chemically joined in fixed proportions. compounds are shown by a combination of numbers and symbols called 'chemical formula;

e.g water = H20= contains 2 Hydrogen (H) atoms, 1 oxygen (O) atom

Reactants: (substances that react) are always shown on the left hand side of the equation 

products: (the products that are made) are on the right hand side of the equation 

the total mass of the products is always equal to the total mass of the reactants. this is because no atoms are lost or made. 

the products are made from exactly the same atoms as the reactants.

e.g magnesium burned in oxygen makes magnesium oxide. 

shown: magnesium+oxygen=magnesium oxide 

mixtures- contains two or more elements or compounds, which are not chemically combined.

filtration- used to seperate soluble solids and insoluble solids (mixture of salt (soluble) and sand (insoluble) can be seperated by dissolving salt in water then filtering the mixture)

crystallisation- used to obtain solid from a solution (salt crystals from dirty salt water, mixture is warmed then water evaportates leaving crystals)

simple distillation- used to obtain a solvent from a solution 

fractional distillation- used to seperate mixtures in which components have different boiling points (oxygen and nitrogen)

chromotography- used to seperate different coloured componenets of a mixture (different colours added to a fizzy drink)