1. Acids and bases
Acids
(Lesson 1)

2. What’s your favorite drink?

3. Food for thought What causes the erosion of the tooth?
What is the reason behind this phenomenon?

4. Lesson objectives
Define acid in terms of ions produced in aqueous solution.
State and describe the chemical properties of acids.
State the physical properties of acids.
Recognize and understand the use of litmus paper and universal indicators.

5. Acids in action! Common Acids Chemical Formula Uses Sulfuric acid
H2SO4
Make detergent, fertilisers and soaps. Used in car batteries.
Hydrochloric acid
HCl
Remove rust from body of a car before painting.
Nitric acid
HNO3
Make fertilisers
Ethanoic Acid (Vinegar)
CH3COOH
Preserve vegetables.
Citric Acid
C6H8O7
Found in fruits- orange and lemon.

6. When water is added into acid…
Sulfuric acid H2SO4 (aq) 2H+ (aq) + SO42-(aq) Hydrochloric acid HCl (aq)  H+ (aq) + Cl-(aq)
What do you notice about these two equations?

7. Sulfuric acid H2SO4 (aq) 2H+ (aq) + SO42-(aq)
1 minute to think and discuss with your partner.
Hint: Three points to note. Focus on the product and the state symbols.
Sulfuric acid H2SO4 (aq) 2H+ (aq) + SO42-(aq)
Hydrochloric acid HCl (aq)  H+ (aq) + Cl-(aq)

8. In both equations,
An anion and a cation is produced.
Cation is H+
The acid and ions formed are in aqueous state.
Sulfuric acid H2SO4 (aq) 2H+ (aq) + SO42-(aq) Hydrochloric acid HCl (aq)  H+ (aq) + Cl-(aq)
Dissociation/ Ionization of acids. i.e. Acid is being ionized in water to form H+ ions and SO42- ions.

9. Definition of an acid
An acid is a substance that produces hydrogen ions, H+(aq), when dissolved in water.
Example HNO3(aq)  H+(aq) + NO3-(aq)
Nitric Acid
Role of water in acidic properties
Acids only display the properties of acids when they are dissolved in water. Acids dissociate in water to produce H+ ions which are responsible for the acidic properties.

10. Chemical properties of acids
Acids can take part in the following reactions:
Acids + metals
Acids + metal carbonates
Acids + bases (Metal oxides / Metal hydroxides)

11. Acid + metals
Acids react with reactive metals to form hydrogen gas and salt.
General word equation metal acid  salt hydrogen
Mg(s) + H2SO4(aq)  MgSO4(aq) +H2(g)
magnesium
Dilute sulfuric acid
Magnesium sulfate
Hydrogen
Note:
A salt is a compound obtained when the hydrogen of an acid is replaced by a metal or an ammonium ion, NH4+
Salt of sulfuric acid  sulfates
Salt of nitric acid  nitrates
Salt of hydrochloric acid  chlorides

12. Acid + metal carbonates
Acid reacts with metal carbonates to form salt, carbon dioxide and water.
General word equation: acid + metal carbonate  salt + water + carbon dioxide
Example: Na2CO3(s) + 2HCl(aq)  2NaCl(aq) + H2O(l) +CO2(g)
Sodium carbonate
Dilute hydrochloric acid
Sodium chloride
Water
Carbon dioxide

13. Acid + bases
Acid reacts with bases (metal oxide or metal hydroxide) to form salt and water only. This reaction is known as neutralisation.
General word equation: Acid + metal oxide/ metal hydroxide  salt + water
Example: ZnO(s) + H2SO4(aq)  ZnSO4(aq) + H2O(l)
Water
Zinc oxide
Dilute sulfuric acid
Zinc sulfate

14. Physical Properties of Acid
Acids have sour taste.
In acids, the free moving ions are able to conduct electricity.

15. Physical Properties of Acid
Acids are corrosive.

16. Physical Properties of Acid
Acids turn damp blue litmus paper red.

17. Acids have pH values of less than 7.

18. What have we learnt today?
What are acids?
Examples of common acids and their uses.
The chemical properties of acids
The physical properties of acids

19. Mini Checkpoint
Write the chemical equations for the following reactions:
Magnesium and hydrochloric acid
Zinc oxide and nitric acid
Calcium carbonate and nitric acid