Equilibria · SHS2 Chemistry

Lesson notes

Learning Objectives

Indicator: 2.1.2.LI.3

By the end of the lesson, learners can:

Distinguish between strong and weak acids in terms of the extent of dissociation in aqueous solution, rate of reaction with reactive metals, electrical conductivity, pH value, and enthalpy change of neutralization.
Distinguish between strong and weak bases using the same five criteria.
Investigate acid and base strength through a circus activity involving a conductivity circuit, universal indicator pH measurements, and heat of neutralization demonstrations.
Explain qualitatively why pH values differ between equimolar solutions of strong and weak acids (or bases).
Relate basicity of an acid (monoprotic, diprotic, triprotic) to its full neutralization capacity without confusing basicity with acid strength.

Sign in with your phone number to read the full note and download the GES plan - free.

Sign in with phone number

Curriculum details

Strand: Physical Chemistry (Strand 1)
Sub-strand: Equilibria (1.2)
Content standard: 2.1.2.CS.2 - Demonstrate knowledge and understanding of the concepts and properties of acids and bases to classify substances as well as determine concentration of analysis through titration. 2.1.2.LO.1 Explain that dynamic equilibrium is attained when the rates of the forward and backward reactions are equal and this principle has industrial applications. 2.1.2.LO.2 Apply your knowledge in acids and bases to classify and describe substances as acids and bases as well as determine the concentration of analyte through titration.
Indicator: 2.1.2.LI.3 - Distinguish between strong and weak acids, strong and weak bases in terms of the extent of dissociation, rate of reaction, electrical conductivity, pH value in aqueous solution and enthalpy change of neutralization value.
Suggested placement: Semester 1, Week 19 (Week 19 of the year)
Our suggestion, laid out in curriculum order across three terms of twelve weeks. NaCCA does not fix the week, so follow your school's scheme of learning.
Curriculum reference: NaCCA curriculum document, p. 72

Exemplars (from the NaCCA curriculum)

Inquiry-Based Learning:
- Explain qualitatively, the differences between weak and strong acids and weak and strong bases in terms of dissociation.
- Using a circus activity, investigate acid or base strengths based on the following methods: a. Conductivity measurement or using the acids or bases as electrolyte with electric bulb in a circuit. b. pH measurement using a pH meter or universal indicator method. c. Use of heat of neutralisation value.
- Discuss basicity of acids and relate it to the strength of acids.
Teaching and Learning Materials:
- * Worksheets with illustrative examples of Arrhenius,
- Bronsted-Lowry and Lewis acids and bases for
- Learners to identify * Fruits * Vegetables * Common acids (HCl, HNO , H SO CH COOH,
- H CO , 2 3 * Bases * Universal indicator with pH colour chart * Litmus papers * Ammonium compound (e.g., ammonium chloride) * Bases: NaOH(aq), KOH(aq), Ca(OH) , NH * Zinc chips, iron filings, magnesium ribbon * pH meter * A simple electric circuit with electric bulb/ lamp, beakers, wire, key/switch
- 3 2 4, 3
- 2 3
- * Mixture of Na CO and * Methyl orange and phenolphthalein
- Burette * Pipette * Conical flask * Droppers * Retort stand and clamp * Pipette filler * White tile * Wash bottle with distilled * Calculator
- NaHCO ) 2 3 3 indicators
- water
Assessment (2.1.2.AS.3). The document marks these depth-of-knowledge levels for this indicator: Level 2 Skills of conceptual understanding.