Acids and Alkalis

• Alkalis

  • Many alkalis are metal hydroxide solutions
  • An alkali can be described as a soluble base
  • A base neutralises an acid forming a salt and water
• Common substances at home that contain alkalis

  • toothpaste
  • drain cleaner
  • oven cleaner
• Solution Colour of litmus

  • acid red
  • neutral purple
  • alkali blue
• Word equation


  • Summarises a reaction by writing the names of the substances you start with and the names of the new substances that are made
  • Reactants are written on the left side, products on the right side
  • An arrow means 'react to form'
• pH scale


  • A numbered scale from 1 to 14
  • Acids have a pH less than 7
  • Neutral solutions have pH 7
  • Alkalis have a pH more than 7
• Salts

  • Are made when an acid reacts with an alkali or a base
  • Salt names are made of two words
  • The first part of the salt name is the same as the metal in the alkali or base
  • The second part of the salt name comes from the acid
• Acids

  • Have a sour taste
  • Most concentrated acids are corrosive
  • If added to water, they become more dilute
  • Dilute acids are less hazardous
  • Many dilute acids are irritant
• Neutralisation


  • This is a reaction between an acid and an alkali
  • It is also a reaction between an acid and a base
• Neutralisation in everyday life

  • Antacids are indigestion remedies
  • Soil can become too acidic for some crops to grow
  • Toothpaste contains a mild alkali to neutralise the acid in our mouths
  • Alkalis are used to neutralise acidic gases from power stations
  • Sulfuric acid reacts with iron oxide in rust and removes it from the surface of an object
• Indicators

  • Change colour and can be used to detect acids, alkalis, and neutral solutions
  • Litmus is a common indicator
• Common substances at home that contain acids

  • citric acid
  • vinegar
  • fizzy drinks
  • car battery acid