Physics Paper 2 Revision Document
This revision guide is designed for Grade 12 Physical Sciences Paper 2 (Chemistry),
specifically focusing on the core CAPS curriculum for Term 2. It covers Organic
Chemistry and the Rate and Extent of Chemical Change.
1. Organic Molecular Structures
Organic chemistry is the study of carbon-based compounds. Every carbon atom must
form exactly four covalent bonds.
• Key Definitions
o Homologous series: A series of organic compounds that can be
described by the same general formula and where each member differs
from the next by a 𝐶𝐻2 group.
o Functional group: A bond or an atom or a group of atoms that determines
the physical and chemical properties of a group of organic compounds.
o Isomers: Compounds with the same molecular formula but different
structural formulae.
• Naming Conventions (IUPAC System)
o Identify the longest continuous carbon chain (Parent chain).
o Number the chain so the functional group gets the lowest possible number.
o Identify and name substituents (e.g., methyl, ethyl, chloro).
o List substituents alphabetically.
, 2. Physical Properties and Intermolecular Forces
Physical properties like boiling point, melting point, and vapour pressure are
determined by the strength of forces between molecules.
• Types of Intermolecular Forces (IMF)
o London forces: Weakest forces found in non-polar molecules (alkanes,
alkenes, alkynes).
o Dipole-dipole forces: Found in polar molecules (aldehydes, ketones,
haloalkanes, esters).
o Hydrogen bonding: Strongest forces found in alcohols and carboxylic
acids (O-H bonds).
• Boiling Point Trends
o As chain length increases, surface area increases, leading to stronger
London forces and higher boiling points.
o As branching increases, surface area decreases, leading to weaker
London forces and lower boiling points.
o Molecules with hydrogen bonding have significantly higher boiling points
than those with only London or dipole-dipole forces.
3. Chemical Equilibrium
Many chemical reactions are reversible (⇌). Chemical equilibrium is a dynamic state
where the rate of the forward reaction equals the rate of the reverse reaction.
• Le Chatelier’s Principle
o If a system in equilibrium is disturbed (by changing pressure, temperature,
or concentration), the system will shift its equilibrium position to counteract
the change.
• The Equilibrium Constant (𝐾𝑐 )
o For a general reaction 𝑎𝐴 + 𝑏𝐵 ⇌ 𝑐𝐶 + 𝑑𝐷:
[𝐶]𝑐 [𝐷]𝑑
𝐾𝑐 =
[𝐴]𝑎 [𝐵]𝑏
o Only temperature changes the value of 𝐾𝑐 .
o Pure solids and pure liquids are omitted from the 𝐾𝑐 expression (their
concentration is 1).
Practice Problems
Problem 1: Organic Nomenclature and Isomers Consider the compound with the
molecular formula 𝐶4 𝐻10 𝑂. 1.1. Draw the structural formula for a positional isomer of
butan-1-ol. 1.2. Give the IUPAC name for this isomer. 1.3. Identify the homologous
series to which this compound belongs.
This revision guide is designed for Grade 12 Physical Sciences Paper 2 (Chemistry),
specifically focusing on the core CAPS curriculum for Term 2. It covers Organic
Chemistry and the Rate and Extent of Chemical Change.
1. Organic Molecular Structures
Organic chemistry is the study of carbon-based compounds. Every carbon atom must
form exactly four covalent bonds.
• Key Definitions
o Homologous series: A series of organic compounds that can be
described by the same general formula and where each member differs
from the next by a 𝐶𝐻2 group.
o Functional group: A bond or an atom or a group of atoms that determines
the physical and chemical properties of a group of organic compounds.
o Isomers: Compounds with the same molecular formula but different
structural formulae.
• Naming Conventions (IUPAC System)
o Identify the longest continuous carbon chain (Parent chain).
o Number the chain so the functional group gets the lowest possible number.
o Identify and name substituents (e.g., methyl, ethyl, chloro).
o List substituents alphabetically.
, 2. Physical Properties and Intermolecular Forces
Physical properties like boiling point, melting point, and vapour pressure are
determined by the strength of forces between molecules.
• Types of Intermolecular Forces (IMF)
o London forces: Weakest forces found in non-polar molecules (alkanes,
alkenes, alkynes).
o Dipole-dipole forces: Found in polar molecules (aldehydes, ketones,
haloalkanes, esters).
o Hydrogen bonding: Strongest forces found in alcohols and carboxylic
acids (O-H bonds).
• Boiling Point Trends
o As chain length increases, surface area increases, leading to stronger
London forces and higher boiling points.
o As branching increases, surface area decreases, leading to weaker
London forces and lower boiling points.
o Molecules with hydrogen bonding have significantly higher boiling points
than those with only London or dipole-dipole forces.
3. Chemical Equilibrium
Many chemical reactions are reversible (⇌). Chemical equilibrium is a dynamic state
where the rate of the forward reaction equals the rate of the reverse reaction.
• Le Chatelier’s Principle
o If a system in equilibrium is disturbed (by changing pressure, temperature,
or concentration), the system will shift its equilibrium position to counteract
the change.
• The Equilibrium Constant (𝐾𝑐 )
o For a general reaction 𝑎𝐴 + 𝑏𝐵 ⇌ 𝑐𝐶 + 𝑑𝐷:
[𝐶]𝑐 [𝐷]𝑑
𝐾𝑐 =
[𝐴]𝑎 [𝐵]𝑏
o Only temperature changes the value of 𝐾𝑐 .
o Pure solids and pure liquids are omitted from the 𝐾𝑐 expression (their
concentration is 1).
Practice Problems
Problem 1: Organic Nomenclature and Isomers Consider the compound with the
molecular formula 𝐶4 𝐻10 𝑂. 1.1. Draw the structural formula for a positional isomer of
butan-1-ol. 1.2. Give the IUPAC name for this isomer. 1.3. Identify the homologous
series to which this compound belongs.
