Acids and Alkalis

• The characteristics of an acid:
  - Sour taste
  - Able to conduct electricity
  - Turns blue litmus paper red
  - Reacts with metals, carbonate or alkalis
• The common acids used in the school laboratory are sulfuric acid (H2SO4), nitric acid (HNO3) and hydrochloric acid (HCl).

• The characteristics of an alkali:
  - Bitter taste
  - Soapy feeling
  - Turns red litmus paper blue
  - Corrosive

• Universal indicator is used to test the acidity or alkalinity of a solution by showing different colour corresponding to different pH values.
• It is red in strong acids, pale green in neutral and blue or violet in strong alkalis.