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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

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

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

pH scalepH scalepH scalepH scale

pH scalepH scale

pH scalepH scalepH scalepH scale

pH scalepH scale

pH scalepH scalepH scalepH scale

pH scalepH scale

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

Neutralisation – Hydrochloric acidNeutralisation – Hydrochloric acidNeutralisation – Hydrochloric acidNeutralisation – Hydrochloric acid

NeutralisationNeutralisation

Neutralisation – Sulphuric acidNeutralisation – Sulphuric acidNeutralisation – Sulphuric acidNeutralisation – Sulphuric acid

NeutralisationNeutralisation

Neutralisation – Nitric acidNeutralisation – Nitric acidNeutralisation – Nitric acidNeutralisation – Nitric acid

NeutralisationNeutralisation

Neutralisation – FertiliserNeutralisation – FertiliserNeutralisation – FertiliserNeutralisation – Fertiliser

NeutralisationNeutralisation

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.

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

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

QuizQuizQuizQuiz

QuizQuiz