Lecture on Acids and Alkalis

Types of Acids

• Sulfuric Acid: Found in car batteries.
• Citric Acid: Present in citrus fruits like lemons and limes.
• Hydrochloric Acid: Located in the stomach.
• Ethanoic Acid: The main component in vinegar.
• Carbonic Acid: Found in fizzy drinks.

Common Characteristics

• All acids are sour.

Types of Alkalis

• Sodium Hydroxide: Found in toothpaste and cleaning products like bleach.
• Potassium Hydroxide: Present in soap.

Common Characteristics

• All alkalis are soapy.

Safety Considerations

• Everyday safe items: fizzy drinks, vinegar, fruits, soaps, toothpastes.
• Dangerous items: car batteries, cleaning products.
• Safety Symbols:
  • Irritant: Requires washing if it contacts skin.
  • Corrosive: Requires protective equipment like gloves and goggles.

Common Laboratory Acids

• Hydrochloric Acid (HCl)
• Sulfuric Acid (H2SO4)
• Nitric Acid (HNO3)
• Commonality: All contain hydrogen.

Common Laboratory Alkalis

• Sodium Hydroxide
• Ammonium Hydroxide
• Calcium Hydroxide
• Commonality: All contain hydroxide.

Identifying Acids and Alkalis

• Universal Indicator: Helps differentiate acids and alkalis.
  • Color Changes:
    • Red, orange, yellow indicate acids.
    • Green, blue, purple indicate alkalis.
• pH Scale:
  • Range 0 to 6: Acids (red to yellow).
  • Range 8 to 14: Alkalis (dark green to purple).
  • pH 7: Neutral (e.g., pure water).

Strength of Acids and Alkalis

• Acids:
  • Weak: Close to pH 7, e.g., tea, coffee.
  • Strong: Vinegar, stomach acid, car battery acid.
• Alkalis:
  • Weak: Near pH 7, e.g., toothpaste, soap.
  • Strong: Down the scale, e.g., bleach.

Conclusion

• The pH scale and universal indicator help determine whether a substance is an acid or an alkali, and its strength.

Additional Resources

• Websites:
  • GCSE Revision Monkey
  • Science Surgery for Key Stage 3 resources and videos.