C5: From Chemistry to Electricity

• An element is oxidised when it gains oxygen
• An element is reduced when it loses oxygen or gains hydrogen
• an element is oxidised when it loses electrons
• an element is reduced when it gains electrons
• OIL RIG

  Oxidation Is Loss

  Reduction Is Gain
• A chemical property is a characteristic of a substance that is observed during a reaction in which the chemical composition or identity of the substance is changed.
• Reactivity series: Potassium, Sodium, Lithium, Calcium, Magnesium, Aluminium, Carbon, Zinc, Iron, Lead, Hydrogen, Copper, Silver, Gold
• Potassium, lithium and sodium are highly reactive with water and oxygen. The oil acts as a barrier to stop the metals reacting with the water or oxygen.
• Li + H2O --> fizzes and moves on surface of water (prod. hydrogen) ALKALI
• Na + H2O --> fizzes and moves on surface of water (prod. hydrogen) ALKALI
• Ca + H2O --> fizzes and moves on surface of water (prod. hydrogen) ALKALI
• K + H2O --> fizzes and moves on surface of water (prod. hydrogen) ALKALI
• Reactivity of group 1 metal increases down the group.
• Reactivity of group 3 metals also increases down the group.
• RXN

  A) no change

  B) Reaction

  C) Reaction

  D) Reaction

  E) Reaction

  F) Reaction

  G) Reaction

  H) no change

  I) no change

  J) no change

  K) no change

  L) no change

  
• Two things needed for rust: Water + Air
• Rust is iron oxide, Fe2O3
• Preventing rust: SURFACE PROTECTION Cover with oil, plastic, paint, plating with metal (eg: galvanisation with zinc)
• Preventing rust: SACRIFICIAL PROTECTION
• Preventing rust: CATHODIC PROTECTION
• Cathodes reduce
• Anodes oxidise
• electrolytes conduct current
• If anion is a halogen, halogen is produced
• if anion is not a halogen, oxygen is produced
• If cation is more reactive than hydrogen, hydrogen is produced
• if cation is less reactive that hydrogen, that metal is produced