Chemistry OCR AS

A catalyst increases the rate of both forward and reverse reactions in an equilibrium by the same amount, resulting in an unchanged position of equilibrium.

A technique used to determine the elemental composition of a sample, often by combustion and subsequent measurement of the resulting gases.

A tabular arrangement of the chemical elements, ordered by their atomic number, electron configuration, and recurring chemical properties.

A state in a closed system when the rate of the forward reaction is equal to the rate of the reverse reaction and the concentrations of reactants and products do not change.

A spectrum of the infrared region of the electromagnetic spectrum, providing information about the functional groups present in a molecule.

Expressions for the equilibrium constant, Kc, for homogeneous reactions and calculations of the equilibrium constant, Kc, from provided equilibrium concentrations.

Saturated hydrocarbons containing only single bonds between carbon atoms.

A measurement of the masses of particles in a sample, used to identify the components of a substance.

Substances that increase the rate of a chemical reaction without being consumed in the overall reaction, and allow the reaction to proceed via a different route with lower activation energy.

International Union of Pure and Applied Chemistry; an international federation of National Adhering Organizations that represents chemists in individual countries.

Unsaturated hydrocarbons containing a C=C bond comprising a π-bond and a σ-bond, with restricted rotation of the π-bond.

The branch of chemistry that deals with the study of carbon compounds and their properties.

The heat energy change in a reaction at constant pressure, including enthalpy of reaction, formation, combustion, and neutralization, which can be exothermic (negative ∆H) or endothermic (positive ∆H).

A principle used to deduce qualitatively the effect of a change in temperature, pressure, or concentration on the position of equilibrium for homogeneous equilibria.

The limitations of radical substitution in synthesis by the formation of a mixture of organic products, in terms of further substitution and reactions at different positions in a carbon chain.

The speed at which a chemical reaction takes place, measured by the rate of formation of the product or the rate of disappearance of the reactants.

The process by which a nucleophile replaces an atom or group in a compound, involving the donation of an electron pair.

The relative positioning of atoms and the bonds between them, such as the formula for ethanol: HCHHCHOH.

Used to identify the E and Z stereoisomers.

Physical states under standard conditions, which can be considered as 100 kPa and a stated temperature, 298 K.

Represent species that are radicals in mechanisms. Dots, •, are required in all instances where there is a single unpaired electron.

The enthalpy change associated with the formation of 1 mol of water from neutralisation, ∆neutH.

Explanation of the tetrahedral shape and bond angle around each carbon atom in alkanes in terms of electron pair repulsion.

Refers to the presence of multiple carbon–carbon bonds, including C=C, C/C and aromatic rings.

A lattice structure in which atoms are bonded together by strong covalent bonds, forming a network solid. This structure results in very high melting and boiling points, insolubility in water, and lack of electrical conductivity.

Homogeneous catalysts are in the same phase as the reactants, while heterogeneous catalysts are in a different phase. Catalysts have great economic importance and benefits for increased sustainability by lowering temperatures and reducing energy demand from combustion of fossil fuels with resulting reduction in CO2 emissions.

The reaction in which a compound reacts with water, causing a chemical breakdown due to a reaction with water molecules.

The simplest algebraic formula of a member of a homologous series, such as CnH2n+2 for an alkane.

The system of naming chemical compounds.

Chlorine is used in water treatment for killing bacteria, but this use comes with associated risks such as hazards of toxic chlorine gas and possible risks from the formation of chlorinated hydrocarbons.

The energy required to break a particular bond in one mole of gaseous molecules.

Values used to interpret electronegativity, with the understanding that electronegativity increases towards F in the periodic table.

Covalent bonding is the strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms. It involves the construction of 'dot-and-cross' diagrams to describe single covalent bonding, multiple covalent bonding, and dative covalent (coordinate) bonding. The term 'average bond enthalpy' is used as a measurement of covalent bond strength, with larger values indicating stronger covalent bonds.

The breaking of 1 mol of bonds in gaseous molecules.

Solid structures of covalently bonded molecules attracted by intermolecular forces, as seen in substances like I2 and ice.

Ions formed by the fragmentation of a larger molecule in a mass spectrometer.

The variation in melting points across Periods 2 and 3 can be explained by the change in bonding from giant metallic to giant covalent to simple molecular lattice. As the bonding changes from metallic to covalent to molecular, the strength of the bonds and forces between particles decreases, leading to lower melting points.

The amount of heat absorbed or released in a chemical reaction under constant pressure.

Strong electrostatic attraction between cations (positive ions) and delocalised electrons, forming a giant metallic lattice structure.

Addition polymerisation is a process in which unsymmetrical alkenes and substituted alkenes undergo polymerisation to form addition polymers. The repeat unit of an addition polymer is deduced from a given monomer, and the monomer that would produce a given section of an addition polymer can be identified.

Specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules.

Heating under reflux is a technique used in organic chemistry where a reaction mixture is heated while being cooled to condense the vapors and return them to the reaction vessel.

An electron pair acceptor.

Redistillation is the process of purifying a liquid by heating it to vaporize and then condensing the vapor to obtain a more pure form of the liquid.

Using diagrams to show clearly the movement of an electron pair with ‘curly arrows’ and relevant dipoles. Curly arrows should start from a bond, a lone pair of electrons, or a negative charge.

Reactions in terms of enthalpy changes associated with the breaking and making of chemical bonds.

The process of identifying the components of a substance or mixture, especially the identification of ions in an unknown compound through various chemical reactions and techniques.

The arrangement of elements by increasing atomic (proton) number, showing repeating trends in physical and chemical properties, and having similar chemical properties in groups.

The replacement of one or more atoms or groups in a compound by another atom or group.

An infrared spectrum of an organic compound can be used to identify different functional groups, such as an alcohol from the absorption peak of the O-H bond, an aldehyde or ketone from the absorption peak of the C=O bond, and a carboxylic acid from the absorption peak of the C=O bond and a broad absorption peak of the O-H bond. Most organic compounds produce a peak at approximately 3000 cm–1 due to absorption by C-H bonds.

Reactions that can proceed in both the forward and reverse directions, and at chemical equilibrium, the concentrations of the reactants and products remain constant over time.

The energy required to break a specific type of carbon-halogen bond, which influences the rate of hydrolysis of primary haloalkanes.

Quickfit apparatus refers to a range of laboratory glassware used for distillation, reflux, and other organic synthesis techniques.

Saturated hydrocarbons with single bonds between carbon atoms.

The enthalpy change associated with the formation of 1 mol of a compound from its elements, ∆fH.

Functional groups are specific groups of atoms within a molecule that are responsible for the characteristic chemical reactions of that molecule.

Average bond enthalpy is a measurement of covalent bond strength, with larger values indicating stronger covalent bonds. However, definition and calculations are not required for this term.

Refers to single carbon–carbon bonds only.

In terms of one bonding atom receiving both electrons from the bonded pair.

Processes and techniques needed to identify specific ions in an unknown compound, including the reactions and precipitation methods for anions such as CO3^2-, SO4^2-, Cl-, Br-, and I-, as well as the reaction for cations like NH4+.

A plot of the ion signal as a function of the mass-to-charge ratio, providing information about the mass and structure of molecules.

Infrared spectroscopy is a technique where infrared (IR) radiation causes covalent bonds to vibrate more and absorb energy. It is used to identify various functional groups in organic compounds by analyzing the absorption peaks of specific bonds such as O-H, C=O, and C-H bonds.

A series of organic compounds with the same functional group and similar chemical properties, in which the members differ by a repeating unit (e.g., CH2) in molecular structure.

Solid structures of carbon (diamond, graphite, and graphene) and silicon, consisting of networks of atoms bonded by strong covalent bonds.

An example of stereoisomerism, in terms of restricted rotation about a double bond and the requirement for two different groups to be attached to each carbon atom of the C=C group.

The existence of different compounds that have the same molecular formula but different structural formulae.

Alcohols can be oxidized by an oxidizing agent such as Cr2O72−/H+ to form aldehydes and carboxylic acids. Primary alcohols are oxidized to form aldehydes and then carboxylic acids, while secondary alcohols are oxidized to form ketones. Tertiary alcohols are resistant to oxidation.

Ionic bonding is the electrostatic attraction between positive and negative ions, leading to the construction of 'dot-and-cross' diagrams. It results in solid structures of giant ionic lattices, with oppositely charged ions strongly attracted in all directions. This bonding affects the physical properties of ionic compounds, including melting and boiling points, solubility, and electrical conductivity in solid, liquid, and aqueous states.

A molecule with polar bonds that do not cancel out, resulting in an overall dipole.

Intermolecular bonding between molecules containing N, O, or F and the H atom of –NH, –OH, or HF, including the role of lone pairs.

The low reactivity of alkanes with many reagents in terms of the high bond enthalpy and very low polarity of the σ-bonds present.

The theory that explains how the rate of a chemical reaction depends on the frequency of collisions between reactant molecules.

The development of the principle that the properties of elements are periodic functions of their atomic number and its acceptance by the scientific community.

A rule that states that in the addition of a protic acid to an unsymmetrical alkene, the major product is formed by the addition of the protic acid to the carbon atom with fewer hydrogen substituents, leading to the formation of a more stable carbocation intermediate.

Mass spectrometry is a technique used to identify the molecular ion peak of an organic compound and determine its molecular mass. It is limited to ions with single charges and to organic compounds containing C, H, and O. Mass spectra may contain a small M+1 peak from the small proportion of carbon-13.

The minimal detail that shows the arrangement of atoms in a molecule, such as CH3CH2CH2CH3 for butane.

The benefits to the environment of the development of biodegradable and photodegradable polymers include reduced dependency on finite resources and alleviating problems from the disposal of persistent plastic waste.

Alcohols undergo combustion reactions to produce carbon dioxide and water. The general equation for the combustion of alcohols is: CnH2n+1OH + (n + 1.25n)O2 → (n + 1)CO2 + (n + 1)H2O

Unsaturated hydrocarbons with at least one carbon-carbon double bond.

A group of atoms responsible for the characteristic reactions of a compound.

A compound containing carbon and hydrogen joined together in straight chains, branched chains or non-aromatic rings.

A compound containing a benzene ring.

Compounds with the same molecular formula but different structural formulae.

A lattice structure in which positive metal ions are surrounded by a sea of delocalized electrons, held together by strong metallic bonds. This structure results in high melting and boiling points, insolubility in water, and excellent electrical conductivity.

The reaction of alkanes with chlorine and bromine by radical substitution using ultraviolet radiation, involving homolytic fission and radical reactions in terms of initiation, propagation, and termination.

The energy required to remove 1 mole of electrons from 1 mole of gaseous atoms. The trend in first ionisation energies across Periods 2 and 3 and down a group can be explained in terms of attraction, nuclear charge, and atomic radius.

Carbocation intermediates are positively charged carbon ions that are formed during the process of addition reactions of H–X to unsymmetrical alkenes. The relative stabilities of primary, secondary, and tertiary carbocations determine the major organic product formed.

Compounds with the same structural formula but with a different arrangement in space.

Organic compounds containing the hydroxyl functional group (-OH). They are polar due to the presence of the hydroxyl group and can form hydrogen bonds with water, leading to their water solubility and relatively low volatility compared to alkanes.

The precipitation reactions of aqueous chloride, bromide, and iodide ions with aqueous silver ions, followed by aqueous ammonia, are used as a test for different halide ions.

A species with an unpaired electron.

Alcohols can undergo substitution with halide ions in the presence of acid to form haloalkanes. For example, NaBr/H2SO4 can be used to facilitate this reaction.

Dot-and-cross diagrams illustrate the arrangement of electrons in molecules and ions, including single covalent bonding, multiple covalent bonding, and dative covalent (coordinate) bonding. These diagrams can show up to six electron pairs, including lone pairs, surrounding a central atom.

Electron pair repulsion theory predicts the shapes of molecules and ions based on the repulsive strengths of bonded pairs and lone pairs of electrons. It explains the shapes and bond angles in molecules and ions, including linear, non-linear, trigonal planar, pyramidal, tetrahedral, and octahedral shapes.

The complete combustion of alkanes, as used in fuels, and the incomplete combustion of alkane fuels in a limited supply of oxygen with the resulting potential dangers from CO.

A distribution that describes the energy distribution of particles in a system at a particular temperature, and its relationship with activation energy.

An electron pair donor, which is attracted to regions of positive charge in a compound.

The reactivity trend of halogens, including chlorine, bromine, and iodine, is illustrated by their reactions with other halide ions. This trend is explained in terms of attraction, atomic radius, and electron shielding.

The process in which ultraviolet radiation causes the breakdown of CFCs, leading to the production of halogen radicals, which contribute to the depletion of the Earth's protective ozone layer.

Hydrocarbons in which the carbon atoms are linked in open chains.

An anhydrous salt is a substance that does not contain water molecules and is used to remove water from organic liquids through the process of drying.

A bond between atoms with different electronegativities, resulting in a permanent dipole within the molecule.

Synthetic routes refer to the specific pathways or series of chemical reactions used to prepare organic compounds from simpler starting materials.

Properties such as the density of ice compared with water, and its relatively high melting and boiling points, resulting from hydrogen bonding.

The techniques and procedures used to determine enthalpy changes directly and indirectly.

The halogens are a group of non-metal elements including fluorine, chlorine, bromine, iodine, and astatine. They exist as diatomic molecules and exhibit a trend in boiling points due to induced dipole-dipole interactions (London forces).

Explanation of the trigonal planar shape and bond angle around each carbon in the C=C of alkenes in terms of electron pair repulsion.

The benefits for sustainability of processing waste polymers include combustion for energy production, use as an organic feedstock for the production of plastics and other organic chemicals, and the removal of toxic waste products, such as the removal of HCl formed during disposal by combustion of halogenated plastics (e.g., PVC).

The simplified organic formula, shown by removing hydrogen atoms from alkyl chains, leaving just a carbon skeleton and associated functional groups.

A separating funnel is a laboratory apparatus used to separate two immiscible liquids by allowing them to settle into separate layers, and then draining the lower liquid out.

A series of organic compounds having the same functional group but with each successive member differing by CH2.

Described as the movement of an electron pair, showing either heterolytic fission or formation of a covalent bond.

Saturated hydrocarbons containing single C–C and C–H bonds as σ-bonds with free rotation of the σ-bond.

The law for construction of enthalpy cycles and calculations to determine indirectly various enthalpy changes.

In terms of each bonding atom receiving one electron from the bonded pair, forming two radicals.

Redox reactions involve the transfer of electrons and changes in oxidation numbers. Halogens, with an outer shell configuration of s2p5, gain one electron in many redox reactions to form 1– ions.

Chemical compounds composed of ions held together by electrostatic forces termed ionic bonding.

A special case of E / Z isomerism in which two of the substituent groups attached to each carbon atom of the C=C group are the same.

The minimum energy required for a reaction to take place.

In the presence of an acid catalyst and heat, alcohols can undergo elimination of water to form alkenes. For example, H3PO4 or H2SO4 can be used as acid catalysts.

The enthalpy change associated with the complete combustion of 1 mol of a substance, ∆cH.

Forces based on permanent dipole–dipole interactions and induced dipole–dipole interactions, also referred to as van der Waals’ forces or London (dispersion) forces.

Explanation of the variations in boiling points of alkanes with different carbon-chain length and branching, in terms of induced dipole–dipole interactions (London forces).

Opportunities for carrying out experimental and investigative work.

Disproportionation refers to the oxidation and reduction of the same element. Examples include the reaction of chlorine with water for water treatment, with cold, dilute aqueous sodium hydroxide to form bleach, and analogous reactions.

Alcohols are classified into primary, secondary, and tertiary based on the number of carbon atoms bonded to the carbon atom bearing the hydroxyl group. Primary alcohols have one carbon atom bonded to the carbon bearing the hydroxyl group, secondary alcohols have two, and tertiary alcohols have three.

The ability of an atom to attract the bonding electrons in a covalent bond.

The mechanism of alkenes by heterolytic fission.

A group of formula CnH2n+1.

An aliphatic compound arranged in non-aromatic rings with or without side chains.

The principle used to determine enthalpy changes.

Explanation of the effect of structure and bonding on the physical properties of covalent compounds with simple molecular lattice structures, including melting and boiling points, solubility, and electrical conductivity.