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Acids and bases Acids and bases (alkalis)(alkalis)
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Hazard signs to learn…Hazard signs to learn…
h i
flammable
Harmful Irritant
Corrosive
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Acids and basesAcids and bases
• 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
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1. Indicators can be used to find out whether a solution is acid, alkaline or neutral
2. 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 scalepH scalepH scalepH scale
pH scalepH scale
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19/04/23Universal Indicator and the pH Universal Indicator and the pH scalescale
Strong acid Strong alkali
Neutral
1 2 3 4 5 6 7 8 9 10 11 12 13 14
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
Stomach acid
Lemon juice
Water Soap Oven cleaner
Baking powder
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pH scalepH scalepH scalepH scale
pH scalepH scale
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pH scalepH scalepH scalepH scale
pH scalepH scale
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pH scalepH scalepH scalepH scale
pH scalepH scale
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1. Acids react with alkaline solutions to form a salt and water
• Hydrochloric acid produces chlorides• Nitric acid produces nitrates• Sulphuric acid produces sulphates2. Ammonia can dissolve in water to
produce an alkaline solution. This can be neutralised with acids to produce ammonium salts
3. Indicators can monitor neutralisation reactions
NeutralisationNeutralisationNeutralisationNeutralisation
NeutralisationNeutralisation
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NeutralisationNeutralisationAn 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
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Neutralisation – Hydrochloric acidNeutralisation – Hydrochloric acidNeutralisation – Hydrochloric acidNeutralisation – Hydrochloric acid
NeutralisationNeutralisation
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Neutralisation – Sulphuric acidNeutralisation – Sulphuric acidNeutralisation – Sulphuric acidNeutralisation – Sulphuric acid
NeutralisationNeutralisation
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Neutralisation – Nitric acidNeutralisation – Nitric acidNeutralisation – Nitric acidNeutralisation – Nitric acid
NeutralisationNeutralisation
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Neutralisation – FertiliserNeutralisation – FertiliserNeutralisation – FertiliserNeutralisation – Fertiliser
NeutralisationNeutralisation
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NeutralisationNeutralisation
• 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
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19/04/23Useful acid-alkali Useful acid-alkali reactionsreactions
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
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Quiz on acids and alkalisQuiz on acids and alkalis
1) This a pH of less than 7
2) This would turn Universal indicator green
3) This is often used in cleaners or soap
4) This would turn Universal Indicator red
5) Sodium hydroxide is a common ____________
6) This would feel soapy on your skin
7) This could be a corrosive
8) This will turn universal indicator purple
9) This would taste sour
10)Lemon juice and vinegar are examples of weak _____
Acid, alkali or both???
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Copy this diagramCopy this diagram
• Label the stomach
• Write down a sentence to explain that antacids neutralise excess stomach acid.
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Reaction of Metals and AcidReaction of Metals and AcidReaction of Metals and AcidReaction of Metals and Acid
Reaction of Metals and Reaction of Metals and AcidAcid
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1. Transition metal oxides and hydroxides do not dissolve in water. They are called bases
2. They react with acids to produce salts that are soluble
3. The excess metal oxide can be filtered off
Metal Oxides & HydroxidesMetal Oxides & HydroxidesMetal Oxides & HydroxidesMetal Oxides & Hydroxides
Metal Oxides & Metal Oxides & HydroxidesHydroxides
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QuizQuizQuizQuiz
QuizQuiz