Chapter 6

• What is the pH value of an acid?

  Less than 7
• What is the pH value of an alkali?

  More than 7
• What taste is associated with acids?

  Sour
• What taste is associated with alkalis?

  Bitter
• How do acids affect blue litmus paper?

  They turn it red
• How do alkalis affect red litmus paper?

  They turn it blue
• What happens when acids react with metals?

  They produce hydrogen gas
• Do alkalis react with metals?

  No, they do not react with metals
• What are examples of acidic and alkaline substances?

  • Acidic: Vinegar
  • Alkaline: Soap
• What is an indicator in chemistry?

  An indicator is a substance that changes color based on the pH of the solution tested
• What are the color changes of phenolphthalein in different pH conditions?

  • Acid & neutral: Colourless
  • Alkali: Pink
• What are the color changes of a universal indicator in different pH conditions?

  • Acid: Red
  • Neutral: Green
  • Alkali: Blue
• What are the color changes of methyl orange in different pH conditions?

  • Acid: Red
  • Neutral and Alkali: Yellow
• What are the color changes of blue litmus paper in different pH conditions?

  • Acid: Red
  • Neutral and Alkali: Blue
• What are the color changes of red litmus paper in different pH conditions?

  • Acid and neutral: Red
  • Alkali: Blue
• What does the pH scale indicate?

  The pH scale shows the strength of acids and alkalis
• How does the pH value relate to the strength of acids?

  The lower the pH value, the stronger the acid
• How does the pH value relate to the strength of alkalis?

  The higher the pH value, the stronger the alkali
• What are some uses of acids in daily life?

  1. Tartaric acid
  2. Carbonic acid (in fizzy drinks)
  3. Sulphuric acid (in car batteries)
  4. Vinegar (used in pickles)
• What are some uses of alkalis in daily life?

  1. Potassium hydroxide (in soap)
  2. Ammonia (in fertilizers)
  3. Sodium hydroxide (in detergents)
  4. Magnesium hydroxide (in antacid pills)