C4 - chemical changes

• what are metal oxides?

  when metals react with oxygen to produce alkaline oxides
• how do metals form positive ions?

  they lose electrons
• what happens if a metal is more reactive?

  it loses electrons more easily
• what is a displacement reaction?

  when a more reactive metal will displace a less reactive metal from a compound
• which metals react well with water?

  potassium, sodium and lithium to form metal hydroxide solution and hydrogen gas

  all three metals float on the surface, fizz and then leave an alkali
• what happens to metals when they react with acids?

  metals above hydrogen in the reactivity series will react with dilute acids to give a metal salt and hydrogen
• what is the order of the reactivity series?

  • potassium
  • sodium
  • calcium
  • magnesium
  • aluminium
  • carbon
  • zinc
  • iron
  • tin
  • lead
  • hydrogen
  • copper
  • silver
  • gold
• which metals can be extracted?

  metals that are below carbon in the reactivity series, to reduce the ore
• how are metals above carbon in the reactivity series extracted?

  electrolysis
• what is oxidation?

  the loss of electrons - this happens at the positive electrode
• what is reduction?

  the gain of electrons - this happens at the negative electrode
• when can half equations be written?

  any reaction where redox has taken place
• what is redox?

  a reaction that takes place between an oxidising substance and a reducing substance
• what is the metallic structure?

  positively charged atoms surrounded by negatively charger electrons
• what are ionic compounds?

  • positive ions which are metal
  • negative ions which are non metal
  • solid ions cant move
  • aqueous and molten ions can move
• what are important ions to remember?

  • ammonium $NH_4^+$
  • hydroxide $OH^-$
  • nitrate $NO_3^-$
  • carbonate $CO_3^{2-}$
  • sulfate $SO_4^{2-}$
  • hydrogen $H^+$
• what is electrolysis?

  splitting an ionic compound using electricity
• what type of matter does the ionic compound have to be for electrolysis?

  molten or dissolved in water so that the ions can move and carry charge
• what are positive metal ions attracted to in electrolysis?

  the negative electrode (cathode)
• what are negative metal ions attracted to in electrolysis?

  the positive electrode ( anode )
• what happens to the electrolysis of lead brominde?

  molten lead bromine can be electrolysed using graphite electrodes

  positive electrode: $2Br^-\ -\ 2e^-\ \rightarrow\ Br_2$

  negative electrode: $Pb^{2+}\ +$$\ 2e^-\ \rightarrow\ Pb$
• what happens at the extraction of aluminium?

  molten aluminium oxide can be electrolysed using carbon electrodes to extract aluminium metal

  positive electrode: $20^{2-}\ \rightarrow\ 0_2\ +$$\ 4e^-$

  negative electrode: $Al^{3+}\ +$$\ 3e^-\ \rightarrow\ Al$
• what has to happen during the extraction of aluminium?

  a lot of energy is required for the electricity and to melt the $Al_20_3$

  carbon anodes have to be replaced as oxygen is made and react with the electrode to make $CO_2$
• what happens at the electrolysis of aqueous solutions?

  the product at the electrode depend on the reactivity of the elements

  negative electrode: positive metal ions and $H^+$ions are attracted. hydrogen is released if the metal is more reactive than hydrogen

  positive electrode: negative ions are attracted. $O_2$ gs is produced unless the solution contains $Cl^-,\ Br^-\ or\ I^-$
• what are strong acids?

  fully ionised in aqueous solutions to produce $H^+$ ions
• what are weak acids?

  partially ionised in aqueous solution to produce $H^+$ ions
• how are salt equations made?

  when a metal above hydrogen in the reactivity series will react with dilute acid to produce a metal salt and hydrogen
• how can an acid be neutralised?

  by and alkali or a base to give a salt + water

  also by reacting with a metal carbonate to give a slat, water and carbon dioxide
• how are soluble salts made?

  • by reacting acids with metals, metals oxides, metal hydroxides or metal carbonates
  • the solid is added in excess until no more will dissolve
  • the remaining solid is filtered out
  • to get the solid salt from the solution, it is allows to crystallise
• what are strong alkali's?

  dissociates completely to form $OH^-$ ions
• what are weak alkali's?

  dissociates partially to form $OH^-$ ions
• what is a titration?

  the volumes of acid and alkali solutions that react with each other can be measured by titration using suitable indicator
• what is the titration method?

  • alkali in burette
  • acid in conical flask measure out with 250cm3 pipette
  • few drops of indicator
  • add alkali to acid until colour changes
  • swirl conical flask
  • add alkali dropwise towards the end
  • not the final burette reading
  • repeat until two reading are within 0.1cm3