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Chemical Changes and Structure

Chemical Changes and Structure. Neutralisation. Learning Intentions. We are learning about the uses of acids in food and drink and the impact on our health. We are learning about different examples of chemicals used to neutralise acids.

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Chemical Changes and Structure

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  1. Chemical Changes and Structure Neutralisation

  2. Learning Intentions • We are learning about the uses of acids in food and drink and the impact on our health. • We are learning about different examples of chemicals used to neutralise acids. • We are learning to predict the chemicals produced during neutralisation reactions

  3. Success Criteria • I can give examples of food and drinks that are acidic and the effect that they have on our health. • I can carry out experiments and write chemical reactions between acids and metals; metal oxides; carbonates and alkalis. • I can state the meaning of the term base and give different examples of bases. • I can predict the products or reactants involved in neutralisation reactions

  4. Neutralising acids Method • Add about 10cm3 of acid to a small beaker • Add 5 drops of pH indicator • Add alkali until a colour change is observed

  5. Neutralising acids Method • Add about 10cm3 of acid to a small beaker • Add 5 drops of pH indicator • Add alkali until a colour change is observed • Repeat with magnesium oxide instead of the alkali

  6. Neutralising acids Result • As the alkali was added, the colour changed from red to orange to green • A solid neutraliser such as magnesium oxide also neutralised the acid but it took longer

  7. Neutralisers • Moves the pH of an acid upwards towards 7 • Moves the pH of an alkali downwards towards 7 • Can be used to assist us in dealing with problems caused by too much acid ie indigestion, acid soil

  8. Neutralising acids with alkalis • acid + alkali salt + water • Salts are ionic compounds which can be produced by neutralisation reactions.

  9. Neutralising acids with alkalis • Eg HCl + NaOH NaCl + H2O From acid From neutraliser

  10. Bases and alkalis • A base is a substance which neutralises an acid • Examples of bases include metal oxides, metal hydroxides, metal carbonates and ammonia • An alkali is formed from a base which dissolves in water

  11. Naming salts • The first part of the name of the salt comes from the base eg • Sodium hydroxide • Magnesium oxide

  12. Naming salts • The acid gives the second part of the name of a salt • Hydrochloric acid HCl chloride • Nitric acid HNO3 nitrate • Sulphuric acid H2SO4 sulphate

  13. Naming salts - examples • Sodium hydroxide neutralises nitric acid

  14. Naming salts - examples • Sodium hydroxide neutralises nitric acid

  15. Naming salts - examples • Sodium hydroxide neutralises nitric acid sodiumnitrate

  16. Naming salts - examples • Magnesium oxide neutralises sulphuric acid

  17. Naming salts - examples • Magnesium oxide neutralises sulphuric acid

  18. Naming salts - examples • Magnesium oxide neutralises sulphuric acid magnesiumsulphate

  19. Naming salts - examples • Nitric acid is neutralised by sodium hydroxide

  20. Naming salts - examples • Nitric acid is neutralised by sodium hydroxide

  21. Naming salts - examples • Nitric acid is neutralised by sodium hydroxide sodiumnitrate

  22. Naming salts - examples • sulphuric acid + sodium hydroxide • Magnesium oxide + nitric acid • Hydrochloric acid + sodium hydroxide • Lithium hydroxide + nitric acid

  23. Naming salts - examples • sulphuric acid + sodium hydroxide sodium sulphate • Magnesium oxide + nitric acid magnesium nitrate • Hydrochloric acid + sodium hydroxide sodium chloride • Lithium hydroxide + nitric acid lithium nitrate

  24. Ions with more than one atom valency 1valency 2valency 3 nitrate NO3- sulphate SO42- phosphate PO43- carbonate CO3-

  25. Naming salts – using symbols • Sodium hydroxide neutralises nitric acid

  26. Naming salts – using symbols • Sodium hydroxide + nitric acid NaOH + HNO3

  27. Naming salts – using symbols • Sodium hydroxide + nitric acid sodium nitrate + water NaOH + HNO3 NaNO3 + H2O

  28. Naming salts – using symbols • Sodium hydroxide + hydrochloric acid NaOH + HCl

  29. Naming salts – using symbols • Sodium hydroxide + hydrochloric acid NaOH + HCl NaCl + H2O

  30. More examples • NaOH + H2SO4 • HNO3 + NaOH • MgO + HCl

  31. More examples • NaOH + H2SO4 NaSO4 + H2O • HNO3 + NaOH NaNO3 + H2O • MgO + HCl MgCl + H2O

  32. Reactions of acids with carbonates • Add 20ml 1M hydrochloric acid to asmall glass beaker

  33. Reactions of acids with carbonates • Add 20ml 1M hydrochloric acid to a small glass beaker • Add calcium carbonate using a spatula until the reaction stops

  34. Reaction of acids with carbonates • Carbonates react with acids to produce a salt, water and carbon dioxide gas. carbonate + acid salt + water + carbon dioxide

  35. Carbonates - examples Calcium + hydrochloric calcium + water + carbon Carbonate acid chloride dioxide

  36. Carbonates - examples Calcium + hydrochloric calcium + water + carbon Carbonate acid chloride dioxide CaCO3 + HCl CaCl2 + H2O + CO2

  37. Reactions of acids with metals • Add 1M hydrochloric acid to a boiling tube until it is approx. ¼ full

  38. Reactions of acids with metals • Add 1M hydrochloric acid to a boiling tube until it is approx. ¼ full • Add 2 pieces of magnesium to the boiling tube

  39. Reactions of acids with metals • Add 1M hydrochloric acid to a boiling tube until it is approx. ¼ full • Add 2 pieces of magnesium to the boiling tube • Hold a lit wooden taper over the end of the boiling tube

  40. Reactions of acids with metals • Magnesium, aluminium, zinc, iron and tin react with acids to produce a salt and hydrogen metal + acid salt + hydrogen magnesium + hydrochloric magnesium + hydrogen acid chloride

  41. Reactions of acids with metal oxides metal oxide + acid salt + water magnesium + hydrochloric magnesium + water oxide acid chloride

  42. Reactions of acids with metal oxides metal oxide + acid salt + water magnesium + hydrochloric magnesium + water oxide acid chloride MgO + HCl MgCl2 + H2O

  43. Salts as ionic compounds • The salts produced by neutralisation reactions are ionic compounds – they contain ions. sodium NaCl Na+Cl- chloride

  44. Salts as ionic compounds • Ions are charged particles. • They either have a positive or negative charge

  45. Aqueous Ionic Compounds • Ions separate in water and move around in solution as separate ions. Sodium chloride (Na+Cl-) could be represented as – Cl- Na+ Na+ Na+ Cl- Cl- Na+ Cl- Cl- Cl- Na+ Cl- Na+ Na+ Na+ Cl- Cl- Na+ Na+ Na+ Cl-

  46. Chemical Tests • The test for carbon dioxide is that it turns limewater cloudy

  47. Chemical Tests • The test for carbon dioxide is that it turns limewater cloudy • The test for hydrogen is that it burns with a pop

  48. Chemical Tests • The test for carbon dioxide is that it turns limewater cloudy • The test for hydrogen is that it burns with a pop • The test for oxygen is that it relights a glowing splint

  49. Electrolysis DC Carbon electrodes copper chloride

  50. Electrolysis • Copper forms at the negative electrode

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