1. Acids and Bases and Salts – revisited 

2. What is an Acid?
A substance which reacts with a base to form salt and water.
Sour taste
pH less than 7
There are two types of acids;
Organic acids – which contain carbon
Mineral acids – which contain inorganic compounds.

3. Organic and Mineral Acids
Ethanoic acid CH3COOH
In vinegar
Methanoic acid HCOOH
In ant and nettle stings
Citric acid C6H8O7
In lemons, oranges etc.
Present in animal and plant material.
weak
Carbonic acid H2CO3
In fizzy drinks
Weak
Hydrochloric acid HCl
Oven cleaner
Dilute form in stomach
Nitric acid HNO3
Ferlilisers and explosives
Sulfuric acid H2SO4
Car batteries, paints and detergents
Strong and corrosive

4. Indicators Litmus (plant extract from lichens) Memory tip
Neutral solutions – purple
Acidic solutions – red
Basic solutions – blue
Memory tip R e
acid /base l u
Litmus paper must always be damp when used....why is this?

5. Other indicators Use your books to complete the following chart.
Colour in Acid
Neutral Colour
Colour in alkali

6. Universal Indicator Mixture of indicator dyes.
Gives a range of colours.

7. pH Scale
Danish chemist Søren Sørensen worked in the Carlsberg breweries and was interested in checking the acidity of beer.
He developed the pH scale.
pH can be measured with universal indicator and also with a pH meter.

8. pH scale and examples
Use your books to help you fill in the following chart. 1 2 3 4 5 6 7 8 9 10 11 12 13 14
water

9. Activity
Answer questions 1 – 7 on page 140

10. Acid and Alkali Solutions
The importance of ions
Both acid and alkai solutions conduct electricity well. This means there is a prsence of ions.
Acids dissolve in water to produce hydrogen ions
HCl H+ (aq) + Cl- (aq)
The term pH is taken from „potenz Hydrogen“ – the power of the hydrogen ion concentration.

11. Alkali Solutions Alkali dissolve in water to produce hydroxide ions .
NaOH Na+ (aq) + OH- (aq)

12. Activity - Determine the ions for the following acids and alkali.
Alkalis
HCl
HNO3
NaOH
KOH

13. Activity
Answer the questions on page 141

14. Metal and Non-Metal Oxides
Read the section on metal and non-metal oxides on pages 141 and 143.
What does amphoteric mean?
Answer question on page 143.