C4 - Chemical Changes

• What occurs when a substance gains oxygen?

  Oxidation
• What occurs when a substance loses oxygen?

  Reduction
• What does the reactivity series of metals show?

  Metals in order of reactivity
• What do metals above hydrogen in the reactivity series do when reacted with acid?

  Produce hydrogen
• How does the reactivity of a metal relate to its reaction with acid?

  More reactive metals react quicker and violently
• What happens to metals below hydrogen in the reactivity series when reacted with acids?

  They don't react
• Which metals primarily react with water?

  Group I and II metals
• Which metal is a borderline case in terms of reactivity with water?

  Aluminium
• What is a displacement reaction?

  More reactive metal displaces less reactive metal
• How are unreactive metals found in the Earth?

  In their natural state
• How can metals less reactive than carbon be extracted?

  Reduction with carbon
• In the reduction of a metal oxide with carbon, what happens to the carbon?

  It gets oxidised to carbon oxides
• In the reduction of a metal oxide with carbon, what happens to the metal oxide?

  It gets reduced to pure metal
• How are metals more reactive than carbon extracted?

  By electrolysis
• How is oxidation defined in terms of electron transfer?

  Loss of electrons
• How is reduction defined in terms of electron transfer?

  Gain of electrons
• What is the general equation for reaction between metals and acids?

  Metal + acid → salt + hydrogen
• What type of reaction is the reaction between metal and acid?

  Redox and displacement
• Which metals in the reactivity series react with acid?

  Those above hydrogen
• What is the general equation for the reaction between metal carbonate and acid?

  Metal carbonate + acid → salt + water + carbon dioxide
• What is the general equation for a neutralisation reaction?

  Base + acid → salt + water
• What is the general equation for the reaction between metal oxides and acids?

  Metal oxide + acid → salt + water
• What type of reaction is a redox reaction?

  Oxidation and reduction occur
• In the reaction of magnesium with hydrochloric acid, what happens to the magnesium?

  It loses electrons and is oxidised
• In the reaction of magnesium with hydrochloric acid, what happens to the hydrogen in HCl?

  It gains electrons and is reduced
• What are the steps in forming a soluble salt?

  • React excess acid with insoluble chemical
  • Filter off the leftovers
  • Crystallise the product
• What do acids produce in aqueous solutions?

  Hydrogen ions
• What do alkalis produce in aqueous solutions?

  Hydroxide ions
• What is a base?

  A compound that neutralises acids
• What is an alkali?

  A soluble base
• What does a pH of 7 indicate?

  Neutral solution
• What does the pH scale measure?

  Acidity/alkalinity of a solution
• What is the general equation for neutralisation in ionic form?

  $H^+$$+$$OH^- → H_2O$
• What is a strong acid?

  Completely ionised in aqueous solution
• What is a weak acid?

  Partially ionised in aqueous solution
• What happens to pH as concentration of H+ increases?

  pH decreases
• What property of a solution does a pH of 7 indicate?

  Neutral solution
• What is the short, ionic form of a neutralisation reaction?

  $H^+$$+$$OH^- \rightarrow H_2O$
• What distinguishes a strong acid from a weak acid?

  Complete vs. partial ionisation in solution
• How does the pH change as the concentration of $H^+$ ions increases?


  The pH decreases