Chemical changes

• Metals​ ​+ oxygen ​->​ ​metal​ ​oxides
• • Reduction=​ loss of ​oxygen​ ​​
  • ​oxidation=​ ​gain​ ​of​ ​oxygen
• Oxidation

  Is

  Loss of electron

  Reduction

  Is

  Gain of electron
• When metals react​ ​with​ ​other​ ​substances,​ ​metal​ ​atoms​ ​form​ ​positive​ ​ions
• Reactivity​ ​of​ ​a metal is​ ​related​ ​to​ ​its​ ​tendency​ ​to​ ​form​ ​positive​ ​ions
• Metals​ ​can​ ​be​ ​arranged​ ​in​ ​order​ ​of​ ​their​ ​reactivity​ ​in​ ​a​ ​reactivity​ ​series
• Reactivity series:

  
• Reaction with water:

  potassium - violent

  sodium - very​ ​quick

  lithium - quick

  calcium - more​ ​slow
• Reaction​ ​with​ ​dilute acid:

  • calcium - very​ ​quick
  • magnesium - quick
  • zinc - fairly​ ​slow
  • iron - more​ ​slow
  • copper - very​ ​slow
• Non-metals​ ​hydrogen​ ​and​ ​carbon​ ​are​ ​often​ ​included​ ​in​ ​the​ ​reactivity series
• A​ ​more​ ​reactive​ ​metal​ ​can displace a​ ​less​ ​reactive​ ​metals​ ​from​ ​a​ ​compound
• Gold,​ ​since​ ​it​ ​is​ ​very​ ​unreactive,​ ​it​ ​is​ ​found​ ​in​ ​the​ ​Earth​ ​as​ ​the​ ​metal​ ​itself
• ​most​ ​metals​ ​are​ ​found​ ​as​ ​compounds​ ​that​ ​require​ ​chemical​ ​reactions​ ​to extract​ ​the​ ​metal
• Metals less reactive than​ ​carbon​ ​can​ ​be​ ​extracted​ ​from​ ​their​ ​oxides​ ​by​ ​reduction with​ ​carbon
• looking​ ​at​ ​just​ ​sodium:​ ​2Na​ ​->​ ​2Na+​ ,​ ​​so​ ​the​ ​ionic​ ​equation​ ​must​ ​be:

  2Na​ ​->​ ​2Na+​ ​​​+​ ​2e-​ ,​ ​​meaning​ ​sodium​ ​has​ ​lost​ ​electrons​ ​&​ ​has​ ​been

  oxidised
• acid​ ​+​ ​metal​ ​->​ ​salt​ ​+​ ​hydrogen
• Redox​ ​reactions​ ​–​ ​ ​one ​substance​ ​is​ ​reduced​ ​and another​ ​substance​ ​is​ ​oxidised
• • Acids​ ​are​ ​​neutralised​​ ​by​ ​alkalis​ ​(e.g​ ​soluble​ ​metal​ ​hydroxides)​ ​and​ ​bases​ ​(e.g insoluble​ ​metal​ ​hydroxides​ ​and​ ​metal​ ​oxides)​ ​to​ ​produce​ ​salts​ ​and​ ​water
• acid​ ​+​ ​alkali​ ​-> salt ​+​ ​water
• acid​ ​+​ ​base​ ​-> salt +​ ​water
• acids​ ​are​ ​​neutralised​​ ​by metal carbonates​ ​to​ ​produce​ ​salts,​ ​water​ ​and​ ​carbon dioxide
• acid​ ​+​ ​metal​ ​carbonate​ ​-> salt +​ ​water​ ​+​ ​carbon​ ​dioxide
• • Hydrochloric​ ​acid​ ​(HCl)​ ​produces​ ​chlorides​ ​(XCl)
  • Nitric​ ​acid​ ​(HNO3​ )​ ​​​​produces​ ​nitrates​ ​(XNO3​ )​
  • Sulfuric ​​acid​​(H2​S​O​4)​​​produces​​ sulfates​​ (XSO​4)​
  • - X = metal
• REMEMBER:​ ​​the​ ​charges​ ​on​ ​the positive ion​ ​from​ ​the base/alkali/carbonate​ ​and​ ​the​ ​negative​ ​ion​ ​from​ ​the​ ​acid​ ​must​ ​add​ ​up​ ​to zero.
• Soluable salts ​can​ ​be​ ​made​ ​from​ ​acids​ ​by​ ​reacting​ ​them​ ​with​ ​solid​ ​insoluble​ ​substances,​ ​such​ ​as metals,​ ​metal​ ​oxides,​ ​hydroxides​ ​or​ ​carbonates
• Acids​ ​produce​ ​H​+​​ ​ions​ ​in​ ​aqueous​ ​solutions
• Alkalis produce​ ​OH​-​​ ​ions​ ​in​ ​aqueous​ ​solutions
• The​ ​pH scale ​(0​ ​to​ ​14)​ ​measures​ ​the​ ​acidity​ ​or​ ​alkalinity​ ​of​ ​a​ ​solution,​ ​and​ ​can​ ​be measured​ ​using​ ​universal​ ​indicator​ ​of​ ​a​ ​pH​ ​probe
• pH scale:

  
• The​ ​volumes​ ​of​ ​acid​ ​and ​alkali solutions​ ​that​ ​react​ ​with​ ​each​ ​other​ ​can​ ​be​ ​measured​ ​by titration​ ​using​ ​a​ ​suitable​ ​indicator.
• 1dm​3 ​=​ ​1000cm​3
• One​ ​mole​ ​of​ ​a​ ​substance​ ​in​ ​grams​ ​the​ ​same​ ​as​ ​its​ ​relative atomic mass​ ​in grams.
• Strong​ ​acid​ ​=​ ​completely​ ​ionised​ ​in​ ​aqueous​ ​solution
• Strong acids

  • hydrochloric​ ​
  • nitric
  • ​sulfuric​ ​acids
• Weak​ ​acid​ ​=​ ​partially​ ​ionised​ ​in aqueous​ ​solution
• Weak Acids

  • Ethanoic​
  • ​citric
  • carbonic​ ​acids
• Stronger​ ​an​ ​acid,​ ​lower​ ​the​ ​pH​ ​(for​ ​a​ ​given​ ​conc.​ ​of​ ​aq.​ ​solutions)
•  As​ ​the​ ​pH​ ​decreases​ ​by​ ​one​ ​unit,​ ​the​ ​H​+ concentration ​of​ ​the​ ​solution​ ​increases​ ​by​ ​a factor​ ​of​ ​10.
• Strong​ ​and​ ​weak​ ​is​ ​NOT​ ​the​ ​same​ ​as​ ​concentrated​ ​and​ ​dilute​ ​–​ ​the​ ​latter​ ​refers to​ ​the​ ​amount​ ​of​ ​substance​ ​in​ ​a​ ​given​ ​volume​ ​,​ ​whereas​ ​the​ ​former​ ​refers​ ​to the​ ​H+​ ​​​ion​ ​conc​ ​in​ ​aq.​ ​solutions
• When​ ​an​ ​ionic​ ​substance​ ​is melted​ ​or​ ​dissolved,​ ​the​ ​ions​ ​are​ ​free​ ​to​ ​move​ ​about within​ ​the​ ​liquid​ ​or​ ​solution.