the term electronegativity; qualitative electronegativity trends in the periodic table; use of relative electronegativity values to predict bond polarity in a covalent bond; relation of overall polarity of a molecule to its shape and the polarity of its individual bonds
intermolecular bonds: instantaneous dipole-induced dipole bonds (including dependence on branching and chain length of organic molecules and Mr), permanent dipole-permanent dipole bonds
intermolecular bonds: the formation of hydrogen bonds and description of hydrogen bonding, including in water and ice
the relative boiling points of substances in terms of intermolecular bonds
This includes an explanation of the boiling points of the halogens.
the term activation enthalpy; enthalpy profiles
Activation enthalpy is related to the energy that pairs of molecules must possess to react when they collide.
the effect of concentration and pressure on the rate of a reaction, explained in terms of the collision theory; use of the concept of activation enthalpy and the Boltzmann distribution to explain the qualitative effect of temperature changes and catalysts on rate of reaction; techniques and procedures for experiments in reaction kinetics including plotting graphs to follow the course of a reaction
the role of catalysts in providing alternative routes of lower activation enthalpy
See also DF(h).
the term homogeneous catalysis and the formation of intermediates
For example, the catalytic action of chlorine radicals on the breakdown of ozone.
calculations, from given data, of values for composition by volume of a component in a gas mixture measured in percentage concentration and in parts per million (ppm)
the recognition of and formulae for examples of members of the following homologous series:
(i) haloalkanes, including systematic nomenclature (ii) amines
the characteristic properties of haloalkanes, comparing fluoro-, chloro-, bromo- and iodo-compounds, considering the following aspects:
(i) boiling points (depend on intermolecular bonds) (ii) nucleophilic substitution with water and hydroxide ions to form alcohols, and with ammonia to form amines
the terms substitution and nucleophile
the use of the SN2 mechanism as a model to explain nucleophilic substitution reactions of haloalkanes using ‘curly arrows’ and partial charges
Knowledge of the SN1 mechanism or of the SN1 or SN2 nomenclature is not required.
the possible dependence of the relative reactivities of the haloalkanes on either bond enthalpy or bond polarity and how experimental evidence determines that the bond enthalpy is more important
homolytic and heterolytic bond fission
the formation, nature and reactivity of radicals and:
(i) explanation of the mechanism of a radical chain reaction involving initiation, propagation and termination (ii) the radical mechanism for the reaction of alkanes with halogens (iii) use of ‘half curly arrows’ in radical mechanisms
the chemical basis of the depletion of ozone in the stratosphere due to haloalkanes; the ease of photodissociation of the haloalkanes (fluoroalkanes to iodoalkanes) in terms of bond enthalpy
*The formation of halogen atoms and the catalytic role of these atoms (and other radicals) in ozone destruction. Simple equations of the breakdown process are required, e.g. *
the formation and destruction of ozone in the stratosphere and troposphere; the effects of ozone in the atmosphere, including:
(i) ozone’s action as a sunscreen in the stratosphere by absorbing high-energy UV (and the effects of such UV, including on human skin) (ii) the polluting effects of ozone in the troposphere, causing problems including photochemical smog
the principal radiations of the Earth and the Sun in terms of the following regions of the electromagnetic spectrum: infrared, visible, ultraviolet
the effect of UV and visible radiation promoting electrons to higher energy levels, sometimes causing bond breaking
calculation of values for frequency, wavelength and energy of electromagnetic radiation from given data