C5 Chemical Changes

• What do metals react with to produce metal oxides?

  Oxygen
• Why are the reactions of metals with oxygen classified as oxidation reactions?

  Because the metals gain oxygen
• What should students be able to explain regarding reduction and oxidation?

  In terms of loss or gain of oxygen
• What do metal atoms form when they react with other substances?

  Positive ions
• How is the reactivity of a metal related to its tendency to form positive ions?

  The more reactive a metal, the more likely it is to form positive ions
• What is the order of reactivity for the metals potassium, sodium, lithium, calcium, magnesium, zinc, iron, and copper?

  • Potassium
  • Sodium
  • Lithium
  • Calcium
  • Magnesium
  • Zinc
  • Iron
  • Copper
• What happens when a more reactive metal is placed in a compound with a less reactive metal?

  The more reactive metal can displace the less reactive metal
• What should students be able to recall regarding the reactions of specific metals with water or dilute acids?

  Reactions of potassium, sodium, lithium, calcium, magnesium, zinc, iron, and copper
• How is the reactivity of metals with water or dilute acids related to their positive ion formation?

  More reactive metals form positive ions more readily
• What is the significance of the reactions of metals with water and acids being limited to room temperature?

  It ensures consistent conditions for observing reactivity
• How are unreactive metals like gold found in the Earth?

  As the metal itself
• How can metals less reactive than carbon be extracted from their oxides?

  By reduction with carbon
• What does reduction involve in the context of metal extraction?

  The loss of oxygen
• What knowledge is limited to regarding the reduction of oxides?

  Using carbon
• What should students be able to identify in terms of oxidation and reduction?

  The substances which are oxidised or reduced
• What is oxidation in terms of electrons?

  The loss of electrons
• What is reduction in terms of electrons?

  The gain of electrons
• What type of reactions do acids undergo with some metals?

  To produce salts and hydrogen
• What should students be able to explain regarding acid reactions in terms of electrons?

  That these are redox reactions
• Which metals should students focus on regarding reactions with hydrochloric and sulfuric acids?

  Magnesium, zinc, and iron
• What happens during the neutralization of acids by alkalis and bases?

  • Acids react with alkalis to produce salts and water
  • Acids react with metal carbonates to produce salts, water, and carbon dioxide
• What determines the particular salt produced in a reaction between an acid and a base?

  The acid used and the positive ions in the base
• What should students be able to predict from given reactants?

  The products of the reaction
• How can soluble salts be made from acids?

  By reacting them with solid insoluble substances
• What is the process for producing a solution of salt from an acid and solid?

  Add solid to the acid until no more reacts, then filter off excess solid
• What can be done to produce solid salts from salt solutions?

  Crystallisation
• What is the required practical for preparing a pure, dry sample of a soluble salt?

  Using a Bunsen burner to heat dilute acid and evaporate the solution
• What do acids produce in aqueous solutions?

  Hydrogen ions (H+)
• What do aqueous solutions of alkalis contain?

  Hydroxide ions (OH–)
• What does the pH scale measure?

  The acidity or alkalinity of a solution
• What is the pH value of a neutral solution?

  7
• How do pH values relate to acids and alkalis?

  Acids have pH values less than 7, and alkalis have pH values greater than 7
• What occurs in neutralisation reactions between an acid and an alkali?

  Hydrogen ions react with hydroxide ions to produce water
• What is used to measure the approximate pH of a solution?

  Universal indicator or a pH probe
• What can be investigated regarding pH changes?

  When a strong acid neutralises a strong alkali
• What is the purpose of titration in chemistry?

  To measure the volumes of acid and alkali solutions that react
• What types of acids and alkalis are used in titrations?

  Strong acids and strong alkalis
• What should students be able to calculate in titrations?

  Chemical quantities involving concentrations in mol/dm³ and g/dm³
• What is a strong acid?

  An acid that is completely ionised in aqueous solution
• What are examples of strong acids?

  Hydrochloric, nitric, and sulfuric acids