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Chemistry

Chemistry. My family and home. Acids and bases (alkalis). Used by the body, used in other processes: such as food, farming and chemical industries. Chemistry Lesson. Safety in chemistry Acids and alkalis (bases) Neutralisation Using indicators Practical work. Hazard signs to learn…. h.

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Chemistry

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  1. Chemistry My family and home

  2. Acids and bases (alkalis) Used by the body, used in other processes: such as food, farming and chemical industries.

  3. Chemistry Lesson • Safety in chemistry • Acids and alkalis (bases) • Neutralisation • Using indicators • Practical work

  4. Hazard signs to learn… h i flammable Corrosive Harmful Irritant

  5. Hazard signs to learn… Radioactive Toxic Dangerous for environment Oxidising

  6. Safety • Irritant- can cause a rash or itching • Harmful-general damage to living organisms • Corrosive-will burn through materials

  7. Safety instructions • Wear goggles • Follow safety instructions

  8. Acids and bases • Acid- A substance that produces hydrogen ions (H+) when it dissolves in water. • Bases- Compounds which react with acids to neutralise them • Alkali- A soluble base, forms hydroxide OH- ions in water. • Neutral-not an acid or base

  9. Symbols in word equations-states of matter • (l) liquid • (g) gas • (s) solid • (aq) aqueous-dissolved in water

  10. Acids and bases (alkalis)

  11. Acid • Examples of acids include : • Vinegar, orange or lemon juice, acid rain, stomach acid, nitric acid, sulfuric acid, hydrochloric acids • Used in car batteries, food and drinks, preserving food, in body.

  12. Acid • Hydrochloric acid is formed when hydrogen chloride is gas dissolves in water. • HCl (g)  H+ (aq) + Cl-(aq)

  13. Alkali (bases) • Examples and uses include: metal hydroxides, metal oxides, cleaning products, stomach antacids, baking powder.

  14. Alkali • Sodium hydroxide is formed when the solid is dissolved in water. • NaOH (s)  Na+ (aq) + OH- (aq)

  15. What is an acid?Is an alkali (OH or H)Give a use of an acid

  16. pH scale • An Indicator is a dye that changes colour • Indicators can be used to find out whether a solution is acid, alkaline or neutral • Universal Indicator can be used to find the pH of a solution • Acid – red, pH less than 7 • Neutral – green, pH = 7 • Alkali – blue, pH greater than 7 pH scale

  17. Universal Indicator and the pH scale 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Strong acid Strong alkali Neutral Universal Indicator is a mixture of liquids that will produce a range of colours to show how strong the acid or alkali is: 0-14 0 Stomach acid Lemon juice Water Soap Baking powder Oven cleaner

  18. pH scale pH scale

  19. pH scale pH scale

  20. pH scale pH scale

  21. Practical 1 • Test chemicals to find pH • Use paper and liquid • Record results in a table

  22. Neutralisation • Acids react with alkaline solutions to form a salt and water • Hydrochloric acid produces chlorides • Nitric acid produces nitrates • Sulphuric acid produces sulphates • Ammonia can dissolve in water to produce an alkaline solution. This can be neutralised with acids to produce ammonium salts • Indicators can monitor neutralisation reactions Neutralisation

  23. Neutralisation Acid + alkali Salt + water Acid + base Salt + water E.g. hydrochloric acid + sodium hydroxide sodium chloride + water An acid and alkali will neutralise each other (if the correct amounts are used):

  24. Neutralisation • Acids and bases neutralise each other. • Acids form H+ (aq) ions in water • Alkalis form OH- (aq) ions in water • Acid + alkali  salt + water • H+ + OH-  H2O • The other parts form the salt.

  25. Neutralisation – Hydrochloric acid Neutralisation

  26. Neutralisation – Sulphuric acid Neutralisation

  27. Neutralisation – Nitric acid Neutralisation

  28. Questions • Write a word equation for adding hydrochloric acid to magnesium hydroxide • Extension : Write a balanced symbol equation for this reaction (difficult) Hint • Mg(OH)2 • MgCl2

  29. Answers • Acid + base  salt + water • Hydrochloric acid + Magnesium hydroxide  magnesium chloride and water • 2HCl + Mg(OH)2MgCl2+2H2O

  30. Neutralisation – Fertiliser Neutralisation

  31. Practical 2 • Titrations and neutralisation

  32. Useful acid-alkali reactions 1) Hydrochloric acid is used in the stomach to help _______. If we eat too many “rich” foods our stomachs create too much ____ – this is called ______. This acid needs to be neutralised by taking indigestion tablets. 2) Soil is naturally acidic, mainly due to acid ____. This can have bad effects on ____ and vegetable growth, so the excess acid may need to be neutralised with an _____ . Words – plant, digestion, indigestion, alkali, rain, acid

  33. Quiz on acids and alkalis Acid, alkali or both??? • This a pH of less than 7 • This would turn Universal indicator green • This is often used in cleaners or soap • This would turn Universal Indicator red • Sodium hydroxide is a common ____________ • This would feel soapy on your skin • This could be a corrosive • This will turn universal indicator purple • This would taste sour • Lemon juice and vinegar are examples of weak _____

  34. Acids and metals • Acid + metal  Salt + hydrogen

  35. Metals and acids • The more reactive the metal, the faster the reaction • The speed of reaction is indicated by the rate at which bubbles of hydrogen are produced. • Test for hydrogen???? • Name of salt depends on metal and acid used

  36. Reaction of Metals and Acid Reaction of Metals and Acid

  37. Hydrochloric acid • Produces Chloride salts • Magnesium + Hydrochloric acid Magnesium Chloride + ________ • _______ + Aluminium +Aluminium Chloride + __________ • ________+ ________  Zinc chloride + _________

  38. Hydrochloric acid • Produces Chloride salts • Magnesium + Hydrochloric acid Magnesium Chloride + hydrogen • Hydrochloric acid + Aluminium +Aluminium Chloride + hydrogen • Hydrochloric acid+ zinc  Zinc chloride + hydrogen

  39. Symbol equations • 2HCl + Mg  MgCl2 +H2 • ____HCl + 2Al  2AlCl3 + 3H2 • 2____ + ____ZnCl2 + H2

  40. Symbol equations • 2HCl + Mg  MgCl2 +H2 • 2HCl + 2Al  2AlCl3 + 3H2 • 2HCl + ZnZnCl2 + H2

  41. Sulfuric acid reactions • H2SO4 + ______ MgSO4 + H2 • 3H2SO4 + 2Al  Al2(SO4)3 + 3H2 • H2SO4 +Zn  ZnSO4 + H2 • Copy and complete write a word equation for each.

  42. Sulfuric acid reactions • H2SO4 + Mg MgSO4 + H2 • 3H2SO4 + 2Al  Al2(SO4)3 + 3H2 • H2SO4 +Zn  ZnSO4 + H2 • Sulfuric acid + magnesium  Magnesium sulfate + hydrogen

  43. Nitric acid • Nitric acid reacts with alkalis, but when reacting with metals it can produce nitrogen oxides.

  44. Metal Oxides & Hydroxides • Transition metal oxides and hydroxides do not dissolve in water. They are called bases • They react with acids to produce salts that are soluble • The excess metal oxide can be filtered off Metal Oxides & Hydroxides

  45. Metal hydroxide • Metal hydroxide + acid  salt + water

  46. Metal oxide • Metal oxide + acid  salt + water

  47. Adding acid to carbonates Calcium carbonate + hydrochloric acid calcium chloride + carbon dioxide + water CaCO3(s) + HCl(aq) CaCl2(aq) + CO2(g) + H2O(l) Carbonates are compounds containing carbon and oxygen. When an acid is added to a carbonate the carbonate starts to fizz. A gas called _________ _______ is produced. 2

  48. Metal carbonate • Metal carbonate + acid  water + salt + carbon dioxide

  49. Quiz Quiz

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