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Acids and bases (alkalis)

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Presentation on theme: "Acids and bases (alkalis)"— Presentation transcript:

1 Acids and bases (alkalis)
17/04/2017 Acids and bases (alkalis)

2 Hazard signs to learn… flammable Corrosive h i Harmful Irritant
17/04/2017 flammable Corrosive h i Harmful Irritant

3 Acids and bases 17/04/2017 Acid- A substance that produces hydrogen ions when it dissolves in water. Bases- Compounds which react with acids to neutralise them Alkali- A soluble base Ion – a charged atom (+ or -), gains or loses an electron

4 Universal Indicator can be used to find the pH of a solution
pH scale 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

5 Universal Indicator and the pH scale
17/04/2017 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 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Stomach acid Lemon juice Water Soap Baking powder Oven cleaner Strong alkali Strong acid Neutral

6 pH scale pH scale

7 pH scale pH scale

8 pH scale pH scale

9 Acids react with alkaline solutions to form a salt and water
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

10 Neutralisation 17/04/2017 An acid and alkali will neutralise each other (if the correct amounts are used: Acid + alkali Salt + water E.g. hydrochloric acid + sodium hydroxide sodium chloride + water

11 Neutralisation – Hydrochloric acid

12 Neutralisation – Sulphuric acid

13 Neutralisation – Nitric acid

14 Neutralisation – Fertiliser

15 Neutralisation Acids and bases neutralise each other.
17/04/2017 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

16 Useful acid-alkali reactions
17/04/2017 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

17 Quiz on acids and alkalis
17/04/2017 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 _____

18 Copy this diagram Label the stomach
17/04/2017 Label the stomach Write down a sentence to explain that antacids neutralise excess stomach acid.

19 Reaction of Metals and Acid

20 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

21 Quiz Quiz

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