Chemical Changes

pH scale 0 - 14

• lower= more acidic
• higher=more alkaline
• neutral=pH 7
• indicator is a dye that changes colour if above or below a certain pH
• acids and bases neutralise each other
• acid= h+ ions in water
• base=pH greater than 7
• alkali is base that dissolves in water form OH- ions in water
• neutralisation: acid+base=salt+water

• Used to find out concentration + whats needed to neutarlise it
• pipette and pipette filler
• add alkali to conical flask + indicator
• funnel to fill burette with acid (known concentration)
• wear safety glasses
• fill below eye level
• record intitial volume
• use burette to add acid slowly
• until end-point (colour change)
• indicator changes colour when all alkali is neutralised
• record final volume
• to increase accuracy look for anomalous results
• first titration= rough to get approximate idea
• repeat more accurately 
• calculate mean
• single indicators:
• (blue in alkalis and red in acids)
• phenolphthalein (pink in alkalis colourless in acids)

• Acids produce protons in water
• Strong acids fully ionise in water = fast rate of reaction so more reactive
• weak do not fully ionise = reversible reaction = equilibrium to the left
• pH (the measure of the conc of hydrogen ions)
• decrease of 1 on pH scale h+ ions x10
• acid strength tells you proportion of acid molecules ionised in water
• concentration= how much acid in water

• Metal oxides and hydroxides= bases (react with acids to form salt and water)
• if they dissolve in water=alkalis
• Acid + metal carbonate = salt + water + carbon dioxide
• insoluble salts can be mad using an insoluble base:
• warm dilute acid
• add insoluble base to acid (in excess)
• filter out excess to get salt solution
• heat solution and then leave to form crystals (crystallisation)

• metals- how easily they loose an electron (form postive ions)
• most reactive:
• potassium - K
• sodium - Na
• lithium - Li
• calcium - Ca
• magnesium - Mg
• carbon - C (non-metal)
• zinc - Zn 
• iron - Fe
• Hydrogen - H (non-metal)
• Copper - Cu 
• acid + metal = salt + hydrogen 
• speed of reaction indicated by bubbles given off
• reactivity= how fast reaction is
• very reactive = explosive
• metal + water = metal hydroxide + hydrogen (less reactive won't react with water)

• Reacting with oxgen forms an oxide (example of oxidation)
• oxides are often ores that metals need to be extracted from
• metal - oxide = reduction reaction
• some can be reduced with carbon
• anything higher than carbon can not be reduced by it (have to use electrolysis)

• if electrons are transferred = redox
• Oxidation
• Is
• Loss
• Reduction
• Is
• Gain (terms of electrons)
• REDuction + OXidation = redox reaction (happen at same time)
• displacement = example of a redox reaction
• (reactive metal "kicks out" less reactive metal)
• metal ion gains electrons
• meatl atom loses electrons 
• use word symbol equations to show this
• ionic equations = useful parts of reactions

• means splitting up with electricity 
• electric current passed throuh molten or dissolved ionic compound
• + ions = cathode (negative electrode) and gain electrons = reuced
• - ions = anode (positive electrode) and losse electrons = oxidised
• when loose/gain form uncharged element and then discharged from electrolyte
• molten ionic compounds can be electrolysed ions free to move + carry current
• metals being ectraced from their ores is very expensive
• need a lot of energy to melt ore and create current
• Aluminium exrtracted from ore bauxite (contains aluminium oxide)
• cryolite added to lower melting point
• molten mixture= free ions =conduct electricity
• Al3+ negative electrode + pick up +3 electrons = aluminium atoms
• O2 goes to positive elctrode -2 electrons = combine to form O2

• will still have hydrogen and hydroxide ions
• cathode= h+ ions and metal ions hydrogen gas produced if more reactive than hydrogen
• if less reactive a solid layer ofp pure metal produced
• at anode if OH- and halide ions (Cl- Br- I-) molecules of cholorine, bromine or iodine formed
• no halide ions= oxygen formed
• cooper sulfate (II) contains Cu2+ SO (2-, 4) H+ and OH- 
• copper metal produced and coats electrode
• no halide ions so anode oxygen and water produced
• chlorine bleaches litmus paper turning it white
• hyrdogen makes a squeaky pop with lighted splint
• oxygen relights a glowing splint
• for half equations make sure elctrons are balanced