Chem

mixture

two or more substances that are not chemically bonded

separation techniques

filtration: removes large insoluble partacles form liquid, eg sand from water

Evaporation leaves behind crystals of a dissolved substance (if heated gently)

Distilation: condensing evaporated solvent and collecting it, (fractional distisation is same but with multiple liquids with diff boiling points

change in state:

heat is required to overcome electrostatic forces of attraction, between partacles to melt/ evaporate

charge and mass of an atom

Atomic and mass numbers

Protons + neutrons = mass number

Atomic number (bottom) = number of protons

electron order

2,8,8,2

metals electrons

metals always donate electrons for an empty outer shell to form pos ions

non metals

always accept electrons to gain full outer shell, can form negative ions or share electrons

Alkalai metals, halogens, noble gasses

G1: alkali metals (all donate outer electon to become +1) , get more reactive as goes down group, as outer electon is further away from nucleus, more easily donated

G7: halogens bacially opposite, boiling points increases down group

G8/0: noble gasses, unreacive as full outer shell

transition metals

can donate diff numbers of electrons

metallic bonding

form a lattice structure (grid of ions) surrounded by delocalized electrons(can move)

ioic bonding

metal atoms donate electrons to non metals to form ions

dot + cross diagrams show electrons on outer shells, metals end up with empty shells, non metal with full outer shell, 8 electrons, CHARGES OF ALL IONS IN AN IONIC COMPOUND MUST ADD UP TO ZERO

forms lattice structure of repeating units of positive and negative ions - forms a crystal (high melting and boiling points, as bonds are strong)

covalent bonding

non metal bonding, atoms share electrons to get a full outer shell, every one consits of a pair of shared electrons, dot + cross diagram can be used , number of electrons reqiured = number of bonds formed,

giant covalent bonds,

forms giant structures that consist of repeating units of atoms, very high melting points as covalent bonds are strong,

alloys are mixtures of diff sized atoms = layers cannot slide over eachother, therefore they are harder,

moles and relative atomic mass

conservation of mass: total mass of reactants= tatal mass of products in reaction, even if gas leaves

moles = grams/relative atomic mass

limiting reactants

less amount of moles, means that it’s the limiting factor,

oxydatiion and reduction, OILRIG

oydation=loss reduction=gain (electrons) nutralistion- makes salt,

crystalisation

heat liquid gently so water evaporates, leaving slat behind

ph scale

stong acid lower ph weak acid high ph

electrolosys

involves passing an electical current through substance to cause oxydiation and reduction at anode and cathode

exothermic and endothermic

endo - cold

exo - hot

bond energies