Introduction to Electrolytes and Acid-Base Theories

Grade 11 · Chemistry

Semester 1 | Period 3 | Week 13

Download the Lessonotes Mobile Liberia app for faster lesson access on Android and iPhone.

Get it on Google Play Get it on the Apple App Store

Subject: Chemistry

Semester: 1

Period: 3

Week: 13

School Name:
Teacher’s Name:
Subject: Chemistry
Grade Level: Grade 11
Week & Period: Week 13, Period III
Date:

Topic: Introduction to Electrolytes and Acids-Bases Theories
Sub-topic:

  • Electrolytes and Non-electrolytes
  • Arrhenius and Bronsted-Lowry Theories of Acids and Bases

 

Learning Objectives
By the end of the lesson, learners should be able to:

  1. Define and distinguish between electrolytes and non-electrolytes
  2. Explain the Arrhenius theory of acids and bases
  3. Explain the Bronsted-Lowry theory of acids and bases
  4. List and describe the general properties of acids and bases

 

Previous Knowledge
Learners have studied basic atomic structure and chemical bonding, and have encountered acids and bases informally in daily life examples.

 

Instructional Materials

  • Conductivity tester
  • Vinegar, lemon juice, soap solution
  • pH paper/Universal indicator
  • Diagrams showing Arrhenius and Bronsted-Lowry theories

Anticipation (Warm-Up) – 5 minutes
Ask:

  • "Why do some substances conduct electricity in water and others don’t?"
  • "What do we call a substance that tastes sour or bitter?" Lead into today’s topic by discussing common household acids and bases.

 

Building Knowledge (Main Lesson) – 25 minutes

  1. Electrolytes and Non-Electrolytes:
    • Electrolytes are substances that dissociate into ions in solution and conduct electricity (e.g., NaCl, HCl).
    • Non-electrolytes do not dissociate into ions (e.g., sugar, ethanol).
    • Demonstrate using a conductivity tester.
  2. Arrhenius Theory:
    • Acids produce H⁺ ions in aqueous solutions; bases produce OH⁻
    • Example: HCl → H⁺ + Cl⁻, NaOH → Na⁺ + OH⁻.
  3. Bronsted-Lowry Theory:
    • Acid: proton donor; Base: proton acceptor.
    • Example: NH₃ + H₂O ⇌ NH₄⁺ + OH⁻.
  4. Properties of Acids and Bases:
    • Acids: sour, react with metals, turn blue litmus red.
    • Bases: bitter, slippery, turn red litmus blue.

 

Learners’ Activities

  • Test household substances using a conductivity tester and litmus paper
  • Identify Bronsted-Lowry conjugate acid-base pairs
  • Classify various substances as electrolyte or non-electrolyte

 

Consolidation (Review and Assessment) – 10 minutes

  • Ask: “What makes a solution an electrolyte?”
  • Quick quiz on Arrhenius and Bronsted-Lowry examples
  • Pair students to explain the difference between the two theories

 

Homework / Assignment:

  1. List 5 electrolytes and 5 non-electrolytes and explain why they belong to each category.
  2. Draw a diagram to show the dissociation of HCl and NaOH in water.
  3. Explain why NH₃ is considered a base according to Bronsted-Lowry.

 

Notes – Detailed and Explained
Electrolytes are compounds that dissolve in water to produce ions, allowing the solution to conduct electricity. Strong electrolytes completely ionize, while weak electrolytes partially ionize.

Non-electrolytes dissolve without forming ions, hence do not conduct electricity. Examples include glucose and ethanol.

Arrhenius Theory defines acids as substances that increase H⁺ concentration in water, and bases as those that increase OH⁻ concentration. However, it is limited to aqueous solutions.

Bronsted-Lowry Theory expands on this by defining acids as proton donors and bases as proton acceptors, making it applicable to a wider range of chemical reactions, including those that don’t occur in water.

Properties of Acids include sour taste, ability to corrode metals, and pH less than 7. Properties of Bases include bitter taste, slippery feel, and pH greater than 7.

 

Expanded Notes / Instructions:

  • Stress the difference between strong and weak electrolytes through demonstration.
  • Include diagrams of acid-base reactions for visual clarity.
  • Reinforce through real-life analogies: lemon juice (acid), baking soda (base).

 

Inclusive / Differentiation:

  • Visual models for learners who benefit from images
  • Simplified definitions and sentence stems for struggling learners
  • Challenge extension: learners propose acids and bases not mentioned in class

 

Teacher’s Reflection (Post-Lesson Questions):

  • Did students correctly classify substances as electrolytes or non-electrolytes?
  • Were they able to differentiate Arrhenius and Bronsted-Lowry theories?
  • Do I need to revisit weak electrolytes and their examples?