Physical Sciences-Acids and Bases

Introduction

  • The declaration of COVID-19 as a global pandemic by the World Health Organisation led to disruptions in effective teaching and learning in many South African schools.
  • Learners in various grades spent less time in class due to phased-in approaches and alternate attendance systems implemented by provinces.
  • Most schools could not complete all relevant content designed for specific grades as per the Curriculum and Assessment Policy Statements.
  • The Department of Basic Education (DBE) collaborated with subject specialists from various Provincial Education Departments (PEDs) to develop this Self-Study Guide to mitigate the impact of COVID-19 on current Grade 12 learners.
  • The Study Guide focuses on critical topics, skills, and concepts necessary for Grade 12, aiming to close pre-existing content gaps and strengthen mastery of subject knowledge.
  • The guide encourages independent learning and mastery of core cross-cutting concepts.

How to Use the Booklet

  • This booklet aims to enhance understanding of Physical Sciences and summarises work necessary for examination purposes.
  • It does not provide full explanations; rather, it highlights essential facts based on examination guidelines.
  • It includes tips and suggested methods for problem-solving and question answering.
  • Students should use their textbooks for in-depth explanations.
  • Authors draw from classroom experience to help improve performance in Acids and Bases.
  • Examples are provided with solutions; students are encouraged to solve them independently before checking the solutions.
  • Persistence is key; resubmit to the exercises if mistakes are made and refer back to relevant theory when necessary.

Acids and Bases

3.1 Extract from the Examination Guidelines

  • Definitions of Acids and Bases:
    • Arrhenius Theory:
    • Acids produce hydrogen ions (H⁺) in solution.
    • Bases produce hydroxide ions (OH⁻) in solution.
    • Lowry-Brønsted Theory:
    • An acid is a proton (H⁺ ion) donor.
    • A base is a proton (H⁺ ion) acceptor.
  • Strong vs Weak Acids/Bases:
    • Strong acids ionise completely in water, forming a high concentration of H₃O⁺ ions.
    • Examples: Hydrochloric acid (HCl), Sulphuric acid (H₂SO₄), Nitric acid (HNO₃).
    • Weak acids ionise incompletely, resulting in a low concentration of H₃O⁺ ions.
    • Examples: Ethanoic acid (CH₃COOH), Oxalic acid ((COOH)₂).
    • Strong bases dissociate completely, forming a high concentration of OH⁻ ions.
    • Examples: Sodium hydroxide (NaOH), Potassium hydroxide (KOH).
    • Weak bases dissociate incompletely.
    • Examples: Ammonia (NH₃), Calcium carbonate (CaCO₃).
  • Concentrated vs Dilute Acids/Bases:
    • Concentrated acids/bases contain a large amount of acid/base relative to the volume of water.
    • Dilute acids/bases contain a small amount of acid/base relative to the volume of water.
  • Reaction Equations:
    • Example of Acid Reaction: HCl(g) + H₂O(ℓ) → H₃O⁺(aq) + Cl⁻(aq) (HCl