1. Acids and bases (alkalis)
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Acids and bases (alkalis)

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

3. Acids and bases
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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
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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
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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.
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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
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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
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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
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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