Lesson Notes By Weeks and Term v5 - Grade 12
Revision and examination preparation – Week 7 focus
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Revision and examination preparation – Week 7 focus
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Subject: Physical Sciences
Class: Grade 12
Term: Term 4
Week: 7
Theme: General lesson support
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This week focuses on intensive revision and exam preparation for topics covered thus far in Grade 12 Physical Sciences. This is a crucial stage, as a solid understanding of the fundamentals forms the bedrock for success in the final examinations. The ability to apply scientific principles to problem-solving is a vital skill, not only for academic success but also for future careers in science, technology, engineering, and mathematics (STEM) fields.
This week’s revision focuses on three core areas: Electrochemistry, Chemical Equilibrium, and Mechanics (specifically Newton’s Laws).
A. Electrochemistry: Electrochemistry deals with the relationship between electrical energy and chemical reactions.
Key concepts include: Electrochemical Cells (Galvanic/Voltaic and Electrolytic): Galvanic cells convert chemical energy into electrical energy through spontaneous redox reactions. Electrolytic cells use electrical energy to drive non-spontaneous redox reactions.
Oxidation and Reduction: Oxidation is the loss of electrons (increase in oxidation number), and reduction is the gain of electrons (decrease in oxidation number).
Oxidizing and Reducing Agents: An oxidizing agent accepts electrons and gets reduced. A reducing agent donates electrons and gets oxidized. Standard Electrode Potential (E°): The measure of the tendency of a half-cell to undergo reduction, measured under standard conditions (298 K, 1 atm pressure, 1 M concentration). Cell Potential (E°cell): The potential difference between the two half-cells in an electrochemical cell. Calculated as E°cell = E°(cathode) - E°(anode). A positive E°cell indicates a spontaneous reaction (Galvanic cell).
Spontaneity: A redox reaction is spontaneous if E°cell > 0 and ΔG 2+ solution and a zinc electrode in a 1.0 M Zn 2+ solution. Calculate the standard cell potential (E°cell) and determine whether the reaction is spontaneous under standard conditions.
Given: E°(Cu 2+ /Cu) = +0.34 V and E°(Zn 2+ /Zn) = -0.76 V Solution: Identify the half-reactions: Reduction: Cu 2+ (aq) + 2e - → Cu(s) (Cathode)
Oxidation: Zn(s) → Zn 2+ (aq) + 2e - (Anode) Calculate E°cell: E°cell = E°(cathode) - E°(anode) = +0.34 V - (-0.76 V) = +1.10 V Determine spontaneity: Since E°cell is positive (+1.10 V), the reaction is spontaneous under standard conditions. This means the galvanic cell will function.