Chemistry

The proportion of incident electromagnetic radiation absorbed by the sample.

A plot of the proportion ofelectromagnetic radiation absorbed by a substance over a range of wavelengths (or frequencies).

An analgesic commonly known as aspirin.

A substance that donates hydrogen ions (protons).

A substance whose colour depends on the concentration of H3O+ ions in solution. Indicators are weak acids and bases; their acid form is one colour and their conjugate base is another.

A reaction involving the transfer of a hydrogen ion (proton) from an acid to a base.

The energy required by reactants for reaction to occur. This energy is needed to break the bonds between atoms in the reactants to allow products to form.

The location on an enzyme’s surface at which reaction occurs. It is usually a flexible hollow or cavity inthe molecule

Reaction of a large number of unsaturated monomers to form a polymer that has the same empirical formula as the monomers.

A reaction in which a molecule binds to an unsaturated hydrocarbon, forming a single carbon-to carbon bond. In this process two reactant molecules becomeone

A base found in nucleic acids such as DNA. It is thecomplementary base of thymine.

The attraction of one substance to the surfaceof another.

An organic compound containing the hydroxy functional group, e.g. ethanol (CH3CH2OH).

A volume of liquid measured by a pipette.

Hydrocarbons with only single bonds between carbon atoms, which have the general formula CnH2n + 2.

Systematic name for an alcohol. An organic compound that has the hydroxy functional group attached to an alkane chain, e.g. ethanol, CH3CH2OH.

Hydrocarbons with one double bond between carbon atoms, which have the general formula CnH2n

Hydrocarbon with one triple bond between carbon atoms, which have the general formula CnH2n – 2.

A compound containing the CONH functional group.This group forms the link between amino acids in proteins.See peptide linkage.

An organic molecule containing the NH2 functional group.

A molecule that contains both an amino group and a carboxy group.

A drug that relieves pain

An anhydrous solid does not contain water molecules in its lattice structure

A common drug used to treat pain, fever and infl ammation, and to reduce blood clotting. Also known aacetylsalicylic acid

An analytical technique that uses light absorption to measure the concentration of a metal in a sample.

An analytical technique that uses light emission to measure the concentration and identity of a metal in a sample.

The value to use in calculating the result of a volumetric analysis. Found by taking the average of three concordant titres.

A substance that accepts hydrogen ions (protons).

• Pairs of complementary bases found in DNA, i.e.
• (i) adenine (A) and thymine (T), or (ii) cytosine (C) and guanine (G).

The highest peak in a mass spectrum; it is assigned an intensity of 100%.

A six-carbon ring, C6H6, containing delocalised electrons. Forms compounds by replacing hydrogens with functional groups.

An item of volumetric equipment that delivers variable volumes of solution accurately

A substance that is produced at the same time as an intended product in the course of a chemical reaction.

A plot of data involving two variables that is used to determine values for one of the variables

A naturally occurring condensation polymer containing carbon, hydrogen and oxygen that has the general formula Cx(H2O)y.

Nuclear magnetic resonance utilising the interaction of the 13C nucleus with an external magnetic field. Used to determine the chemical environment of carbon atoms in compounds.

The functional group COOH.

An organic molecule containing the carboxy functional group, e.g. ethanoic acid (CH3COOH).

The gas used as the mobile phase in gas chromatography.

A substance that increases the rate of a reaction but is not consumed in the reaction

Identification of the chemicals present in a substance or the measurement of their concentration.

Frequency of the signal in the NMR spectrum, relative to the TMS standard.

The Cl functional group.

A molecule derived from an alkane, containing a Cl functional group.

The trace or plot that is obtained when the components of a mixture are separated by chromatography.

A technique for separating the components of a mixture. The components are carried by a mobile phase (gas or liquid) over the adsorbent surface of a stationary phase, which can be solid or liquid.

Clumping of denatured protein molecules to form a suspension.

A chromatographic technique in which the stationary phase is contained in a column, as for example in gas chromatography.

A combination of two or more analytical techniques in the same instrument, e.g. gas chromatography–mass spectrometry.

Rapid reaction with oxygen accompanied by the release of large amounts of heat; burning.

A measure of how much solute is dissolved in a unit quantity of solution.

Formation of a polymer by condensation reactions.

A reaction in which two molecules link together, eliminating a small molecule such as water.

A base found in nucleic acids such as DNA. It is the complementary base of guanine

A change to the structure and shape of a protein that prevents it from functioning.

A five-carbon sugar that is a constituent of DNA.

(DNA) A nucleic acid that carries genetic information in the cells of plants and animals. Each strand is formed by a condensation polymerisation reaction between nucleotide monomers. Hydrogen bonds between complementary bases shape pairs of DNA molecules into a double helix structure.

The breaking of the bonds between a substance and the surface to which the substance is adsorbed

The addition of solvent to make a solution less concentrated.

A liquid used as the mobile phase in chromatography

A display of the wavelengths of light emitted by a substance. For many metals this appears as coloured lines on a black background.

The formula of a compound that indicates the simplest ratio of atoms of each element in the compound

The point during a titration when the indicator changes colour.

A protein molecule that acts as a catalyst for reactions in living things.

A point during a titration when the solutions have been mixed in the mole ratio shown by the reaction equation.

An organic compound containing the ester functional group –COO–.

The chemical reaction between an alcohol (alkanol) and a carboxylic (alkanoic) acid to form an ester as the main product.

A two-carbon member of the alkanol homologous series; found in alcoholic drinks.

A functional group that consists of an oxygen linking two hydrocarbons or sugars

A reagent that is not completely consumed in a reaction.

• The breakdown of sugar solutions, by the
• action of enzymes in yeasts, into ethanol and carbon dioxide

In chemical analysis, a spectrum or analysis that is unique to a particular chemical

A device used to identify organic compounds leaving a GC column. The compounds are burnt in a hydrogen–oxygen flame and are attracted to electrodes, creating an electric current.

The break-up of a molecule into a number of different smaller fragments in a mass spectrometer, the mass of which can be used to identify the molecule.

An atom or group of atoms with at least one unpaired electron; this tends to make them highly reactive.

A form of chromatography in which the mobile phase is a gas. It includes the techniques of gas–liquid chromatography and gas–solid chromatography.

A combined analytical technique in which the mass spectrometer replaces the conventional detector in the gas chromatograph.

A very sensitive form of chromatography that is limited to separating compounds that can be vaporised readily without decomposing. It uses an inert gas as the mobile phase and a viscous liquid as the stationary phase

A chromatographic technique in which the mobile phase is a gas and the stationary phase an adsorbent solid such as alumina or activated charcoal.

The equation that describes the behaviour of a gas: pV = nRT.

An alcohol containing three OH groups. A glycerol molecule can react with three molecules of fatty acids to form a fat molecule.

A carbohydrate that is a means of storing glucose in animals.

A C–O–C link formed when two monosaccharides combine to form a disaccharide.

A type of analysis that involves precipitation and weighing.

A base found in nucleic acids such as DNA. It is the complementary base of cytosine.

An equation involving either an oxidation or a reduction process. The electrons lost or gained in this process are shown in the equation

A very sensitive form of chromatography in which the mobile solvent phase is pumped through the stationary phase under high pressure

A combined analytical technique in which the mass spectrometer replaces the conventional detector in HPLC.

A type of protein. DNA wraps around histones to form chromosomes.

Organic compounds with the same functional groups in which each member of the groups differs from the previous member by CH2

A strong dipole–dipole attraction that forms between molecules when hydrogen is bonded to one of the electronegative elements oxygen, nitrogen or fluorine.

A reaction in which water is a reactant

The OH functional group.

An analytical technique that uses the infrared part of the electromagnetic spectrum.

The reagent that is completely consumed in a reaction and which determines the amounts of products formed.

A viscous liquid used as the stationary phase in chromatography. The components of a mixture undergo adsorption to this liquid as they are carried along by the mobile phase.

An instrument designed to measure the mass-to-charge ratio of particles.

An analytical technique that uses the mass-to-charge ratio of atoms, molecules and fragments of molecules to identify substances

A graph of data produced from a mass spectrometer indicating the abundance of each particle and the mass-to-charge ratio.

The phase that moves over the stationary phase in chromatography.

A technique used to analyse materials using the interaction of the nucleus of particular atoms, usually 1H or 13C, with an external magnetic field.

The monomers of DNA, consisting of a phosphate group, deoxyribose sugar and a base (adenine, cytosine, guanine or thymine) bonded together

The CONH functional group between amino acid units in polypeptides and proteins. Also called an amide group.

An analysis to determine the identity of the chemicals present in a substance.

A determination of how much of each chemical present ina substance.

A chemical used to make acetylsalicylic acid (aspirin).

An adsorbent solid such as alumina or activated charcoal which is used as the stationary phase in chromatography. The components of a mixture undergo adsorption to this solid as they are carried along by the mobile phase.

Conditions at which gas pressure is 1.0 atm (101.3 kPa), the concentrations of dissolved species are 1.0 M and the temperature is 25°C.

0°C and 1 atm pressure.

A solid, or a solid that is coated in a viscous liquid, used in chromatography. The components of a mixture undergo adsorption to this phase as they are carried along by the mobile phase.

Chromatography using as the stationary phase a thin layer of fine powder spread on a glass or plastic plate.

A base found in nucleic acids such as DNA. It is the complementary base of adenine

A process used to determine the concentration of a reagent in which one solution is added from a burette to a known volume or mass of another substance

An analytical technique involving measurement of the UV–visible light absorbed by a substance

A dipolar ion formed when the proton on the carboxy group of an amino acid molecule is transferred to the amino functional group, as in +H3NCH2COO–.