2.2.6

The pH Scale

Test yourself

The pH scale

Acids and alkalis all have a pH, which is a number that tells you how strong the acid or alkali is. It starts at zero and goes up to 14.

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The pH scale

  • Anything below 7 is an acid.
    • The lower the number, the stronger the acid.
  • Anything above 7 is an alkali.
    • The higher the number, the stronger the alkali. pH 7 is neutral – these chemicals are neither acid or alkali.
  • Pure water has a pH of 7.
  • Each pH number is also given a colour.
    • The colours on the pH scale are what colour the chemical will go if ‘universal indicator’ is added.
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Common acids

  • Lemon juice.
  • Hydrochloric acid.
  • Sulfuric acid.
  • Nitric acid.
  • Vinegar.
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Common alkalis

  • Soap.
  • Toothpaste.
  • Ammonia.
  • Sodium hydroxide.
  • Lithium hydroxide.
  • Calcium oxide.

Jump to other topics

1Biology

1.1Cells, Tissues & Organs

1.2Reproduction & Variation

1.3Ecological Relationships & Classification

1.4Digestion & Nutrition

1.5Plants & Photosynthesis

1.6Biological Systems & Processes

2Chemistry

2.1Particles

2.2Chemical Reactions

2.3Atoms, Elements, Compounds

2.4The Periodic Table

2.5Materials & the Earth

2.6Reactivity

2.7Energetics

2.8Properties of Materials

3Physics

3.1Energy

3.2Forces & Motion

3.3Waves

3.4Electricity & Magnetism

3.5Matter

3.6Space Physics

4Thinking Scientifically

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