SHS3 Chemistry · Semester 1 Week 1: Equilibria

Lesson notes

Learning Objectives

Indicator: 3.1.2.LI.1 - Explain and undertake calculations on the concepts of pH, and pOH and describe their significance in everyday life.

By the end of the lesson, learners can:

Define pH as the negative logarithm to base ten of the hydrogen ion concentration of a solution and pOH as the negative logarithm to base ten of the hydroxide ion concentration, and write the mathematical expressions pH = -log[H⁺] and pOH = -log[OH⁻].
Describe the pH scale from 0 to 14, identifying values below 7 as acidic, above 7 as basic, and exactly 7 as neutral.
State the ionic product of water (Kw = [H⁺][OH⁻] = 1.0 × 10⁻¹⁴ at 25 °C) and deduce the relationship pH + pOH = pKw = 14.
Calculate the pH and pOH of strong acids and strong bases given their concentrations.
Explain the significance of pH values in everyday life, including acid rain, soil pH, blood, urine, saliva, and household products.

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: 3.1.2.CS.1 - Demonstrate knowledge and understanding of the pH scale in determining the acidity and alkalinity of strong and weak acids, bases and aqueous solutions. 3.1.2.LO.1 Use the knowledge in pH to distinguish between solutions that are acidic, neutral or basic. 5 Gender Equality and Social Inclusion 6 Socio-Emotional Learning 3.1.2.LO.2 Use your knowledge and understanding of concepts in hydration and hydrolysis to determine the types of salts. 3.1.2.LO.3 Use the understanding of hydrolysis of salts to decide on suitable indicator as well as plot and interpret titration curves. 3.1.2.LO.4 Describe oxidation and reduction reactions and apply their principles to electrochemical cells as well as their importance in everyday life.
Indicator: 3.1.2.LI.1 - Explain and undertake calculations on the concepts of pH, and pOH and describe their significance in everyday life.
Suggested placement: Semester 1, Week 1 (Week 1 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. 95

Exemplars (from the NaCCA curriculum)

Digital Learning: Watch a video or listen to a presentation on pH and pOH, how they are calculated and their applications.
Talk for Learning: In a teacher-led discussion, explain pH (as the negative logarithm to the base ten of the hydrogen ion concentration of a solution) and deduce the mathematical expression for it (pH =-log [H+])
Collaborative Learning:
- With the aid of relevant pictures or charts, describe the pH scale making emphasis on the various sections: a. Values below 7, is acidic. b. Values above 7, is basic. c. Exactly 7 is neutral.
- Discuss the ionic product of water and deduce the relationship between pH, pOH and pKw
- Calculate the pH and pOH of strong acids and strong bases.
Inquiry-Based Learning: Research and discuss the significance of the values of pH in everyday life e.g. acid rain and its effect, pH of soil, blood, urine and saliva; shampoo and pharmaceutical products.
Teaching and Learning Materials:
- * pH scale * pH meter
- * Universal indicator * Calculator
Assessment (3.1.2.AS.1). The document marks these depth-of-knowledge levels for this indicator: Level 3 Strategic reasoning.