3.1.1 The pH Scale and Indicators

• What is the pH range for neutral substances?

  7
• Which substance is more acidic, battery acid or lemon juice?

  Battery acid
• What is the pH range of alkalis?

  Greater than 7
• What is the pH scale shown in the image?

  0 to 14
• If a substance has a pH of 5, what type of substance is it?

  Acidic
• How can you determine if a substance is acidic, neutral, or alkaline based on its pH value?

  • pH less than 7 = Acidic
  • pH = 7 = Neutral
  • pH greater than 7 = Alkaline or Basic
• What are the three main categories of the pH scale?

  • Acid
  • Neutral
  • Alkaline or "Basic"
• What are the three distinct types of solutions shown by the pH scale?

  Acidic, Neutral, Alkaline
• How does the pH scale indicate the acidity or basicity of a substance?

  • Lower pH values (0-6) indicate increasing acidity
  • pH 7 is neutral
  • Higher pH values (8-14) indicate increasing basicity or alkalinity
• What is the pH of a neutral solution?

  7
• Acids react with all metals to produce hydrogen gas.

  False
• What is the pH range for human blood?

  7.35-7.45
• What are the key differences between acidic and basic (alkaline) substances?

  • Acidic substances have a pH range of 0-6
  • Basic (alkaline) substances have a pH range of 8-14
  • Neutral substances have a pH of 7
  • Examples of acidic substances include battery acid, stomach acid, lemon juice, vinegar, and soda
  • Examples of basic (alkaline) substances include milk, baking soda, household ammonia, household bleach, and sodium hydroxide
• Indicators change color at a single, fixed pH value.

  False
• What is the pH range for acidic substances?

  0-6
• What is the end-point pH for the indicator thymol blue?

  8.1
• What is the pH range for basic (or "alkaline") substances?

  8-14
• Acids feel slippery to the touch.

  False
• Match the type of solution with its corresponding pH range:

  Acidic ↔️ 0-6

  Neutral ↔️ 7

  Alkaline ↔️ 8-14
• What is the color of the indicator methyl red at higher pH?

  yellow
• What is the end-point pH for the indicator bromocresol green?

  4.7
• What is the color of the indicator bromothymol blue at higher pH?

  blue
• What is a distinctive property of acids regarding their taste?

  Sour taste
• What does pH measure?

  Acidity or alkalinity
• Acids have a bitter taste.

  False
• What is the pH scale used to measure?

  Acidity, neutrality, alkalinity
• Match the common example with its pH value:

  Battery acid ↔️ 0

  Lemon juice ↔️ 2

  Pure water ↔️ 7

  Bleach ↔️ 12
• What is the color of the indicator alizarin yellow at lower pH?

  yellow
• What is the average global surface ocean pH?

  8.1
• What type of reactions do indicators rely on to change color based on pH?

  Reversible reactions
• Arrange the properties of acids and alkalis based on their differences:

  1️⃣ pH: Acid < 7, Alkali > 7

  2️⃣ Taste: Acid - Sour, Alkali - Bitter

  3️⃣ Texture: Acid - Corrosive, Alkali - Slippery
• What color does methyl orange change to in basic solutions?

  Yellow
• How do the pH values of acidic, neutral, and alkaline substances compare?

  Acidic substances have pH values less than 7, neutral substances have pH 7, and alkaline substances have pH greater than 7
• What is the pH range of acids?

  Less than 7
• What happens to the equilibrium position of an indicator when the pH changes?

  It shifts
• What is a common example of an alkali used in cooking?

  Baking soda
• What does the pH scale represent?

  The acidity or basicity of a substance
• What is the pH range for the indicator bromophenol blue?

  • pH range: 2.8 - 4.6
• How does the pH range of an indicator affect its usefulness?

  Indicators with a narrow pH range are more precise, while those with a wider range are more versatile
• What is the pH range for the indicator phenolphthalein?

  8.2 - 10.0