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A Level Chemistry > Definitions > Flashcards

Definitions Flashcards

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1
Q

What is the definition for a catalyst?

A

A substance that alters the rate of a chemical reaction by providing an alternate pathway of a lower energy. It is not used up in a reaction.

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2
Q

What is the definition for activation energy?

A

The minimum energy that a particle needs in order to react; the energy (enthalpy) difference between the reactants and the transition state.

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3
Q

What is the definition for a acid?

A

Bronsted-Lowry = A proton donor; Lewis = an electron pair acceptor.

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4
Q

What is the definition for a base?

A

Bronsted-Lowry = A proton acceptor; Lewis = an electron pair donor

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5
Q

What is the definition for a buffer?

A

A solution that resists change of pH when small amounts of acid or base are added or on dilution.

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6
Q

What is the definition for a calorimeter?

A

An instrument for measuring the heat changes that accompany chemical reactions.

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7
Q

What is the definition for a carbocation?

A

An organic ion in which one of the carbon atoms has a positive charge.

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8
Q

What is the definition for chelation?

A

The process by which a multidentate ligand replaces a monodentate ligand in forming co-ordinate (dative) bonds to a transition metal ion.

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9
Q

What is the definition for chiral?

A

This means ‘handed’. A chiral molecule exists in two mirror image forms that are not superimposable.

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10
Q

What is the definition for chiral centre?

A

An atom to which four different atoms or groups are bonded. The presence of such an atom causes the parent molecule to exist as a pair of nonsuperimposable mirror images.

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11
Q

What is the definition for co-ordinate bond (dative bond)?

A

A covalent bond in which both the electrons in the bond come from one of the atoms forming the bond.

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12
Q

What is the definition for co-ordination number?

A

The number of ligand molecules bonded to a metal ion..

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13
Q

What is the definition for dipole - dipole force?

A

An intermolecular force that results from the attraction between molecules with permanent dipoles.

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14
Q

What is the definition for Displacement reaction?

A

A chemical reaction in which one atom or group of atoms replaces another in a compound, for example,
Zn + CuO –> ZnO + Cu

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15
Q

What is the definition for disproportionation?

A

Describes a redox reaction in which the oxidation number of some atoms of a particular element increases and that of other atoms of the same elements decreases.

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16
Q

What is the definition for dynamic equilibrium?

A

A situation in which the composition of a constant concentration reaction mixture does not change because both forward and backward reactions are proceeding at the same rate.

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17
Q

What is the definition for Electron pair repulsion theory?

A

A theory which explains the shapes of simple molecules by assuming that pairs of electrons around a central atom repel each other and thus take up positions as far away as possible from each other in space.

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18
Q

What is the definition for electronegativity?

A

The ability of an atom to attract a bonded pair of electrons in a covalent bond.

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19
Q

What is the definition for Electrophile?

A

An electron-deficient atom, ion or molecule that takes part in an organic reaction by attacking areas of high electron density in another reactant.

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20
Q

What is the definition for Electrophilic addition?

A

A reaction in which a carbon-carbon double bond is saturated, by the carbon-carbon double bond attacking an electrophile.

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21
Q

What is the definition for Electrostatic forces?

A

The forces of attraction and repulsion between electrically charged particles.

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22
Q

What is the definition for Elimination?

A

A reaction in which an atom or group of atoms is removed from a reactant.

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23
Q

What is the definition for Exothermic?

A

Describes a reaction in which heat energy is given out as the reactants change to products - therefore the temperature rises.

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24
Q

What is the definition for Fatty acid?

A

A long-chain carboxylic acid.

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25
Q

What is the definition for Free radical?

A

A chemical species with an unpaired electron- usually highly reactive.

26
Q

What is the definition for Endothermic?

A

Describes a reaction in which heat energy is taken in as the reactants change to products, the temperature therefore drops.

27
Q

What is the definition for Enthalpy change?

A

A measure of heat energy given out or taken in when a chemical or physical change occurs at constant pressure.

28
Q

What is the definition for Entropy?

A

A numerical measure of disorder in a chemical system.

29
Q

What is the definition for Equilibrium mixture?

A

The mixture of reactants and products formed when a reversible reaction is allowed to proceed in a closed container until no further change occurs. The forward and backward reactions are still proceeding but at the same rate.

30
Q

What is the definition for Homologous series?

A

A set of organic compounds with the same functional group. The compounds differ in length of their hydrocarbon chains.

31
Q

What is the definition for Hydration?

A

A reaction in which water is added.

32
Q

What is the definition for Hydrogen bonding?

A

A type of intermolecular force in a which a hydrogen atom interacts with either N, O or F.

33
Q

What is the definition for Hydrolysis?

A

A reaction of a compound or ion with water.

34
Q

What is the definition for Incomplete combustion?

A

A combustion reaction in which there is insufficient oxygen for all the carbon in the fuel to burn to carbon dioxide. Carbon monoxide and/or carbon (soot) are formed.

35
Q

What is the definition for Ionisation energy?

A

The energy required to remove an electron from one mole of gaseous ions to form one mole of gaseous +1 ions.

36
Q

What is the definition for Isomer?

A

One or two (or more) compounds with the same molecular formula but different arrangement of atoms in space.

37
Q

What is the definition for Ketone?

A

An organic compound with the general formula R2CO in which there is a C=O double bond.

38
Q

What is the definition for Ligand?

A

An atom, ion or or molecule that forms a co-ordinate (dative) bond with a transition metal ion using a lone pair of electrons.

39
Q

What is the definition for Maxwell-Boltzmann distribution?

A

The distribution of energies (and therefore speeds) of the molecules in a gas or liquid.

40
Q

What is the definition for Mean bond enthalpy?

A

The average value of the bond dissociation enthalpy for a given type of bond taken from a range of different compounds.

41
Q

What is the definition for Metallic bonding?

A

Describes a chemical bond in which outer electrons are delocalised within the lattice of metal ions.

42
Q

What is the definition for Monomer?

A

A small molecule that combines with many other monomers to form a polymer.

43
Q

What is the definition for Nucleophile?

A

A negative ion or molecule that is able to donate a pair of electrons and takes part in an organic reaction by attacking an electron deficient area in another reactant.

44
Q

What is the definition for Nucleophilic substitution?

A

An organic reaction in which a molecule with a partially positively charged carbon atom is attacked by a reagent with a negative charge or partially negatively charged area (a nucleophile). It results in the replacement of one of the groups or atoms on the original molecule by the nucleophile.

45
Q

What is the definition for Optical isomer?

A

Pairs of molecules that are non-superimposable mirror images.

46
Q

What is the definition for Oxidation?

A

A reaction in which an atom or group of atoms losses electrons.

47
Q

What is the definition for Oxidising agent?

A

A reagent that oxidises (removes electrons from) other species. An oxidising agent is reduced.

48
Q

What is the definition for pH?

A

A scale for measuring acidity and alkalinity.

pH = -log10[H^+] in a solution.

49
Q

What is the definition for Polar?

A

Describes a molecule in which the charge is not symmetrically distributed so that one area is slightly positively charged and another slightly negatively charged.

50
Q

What is the definition for racemate?

A

A mixture of equal amounts of two optical isomers of a chiral compound. It is optically inactive.

51
Q

What is the definition for rate-determining step?

A

The slowest step in the reaction mechanism. It governs the rate of the overall reaction.

52
Q

What is the definition for redox reaction?

A

Short for reduction-oxidation reaction, it describes reactions in which electrons are transferred from one species to another.

53
Q

What is the definition for reducing agent?

A

A reagent that reduces (adds electrons to) another species. The reducing agent is oxidised.

54
Q

What is the definition for reduction?

A

A reaction in which an atom or group of atoms gain electrons.

55
Q

What is the definition for standard molar enthalpy change of combustion?

A

The enthalpy change when 1 mole of a substance is completely burned in oxygen with all reactants and products in their standard states (298K and 100kPa)

56
Q

What is the definition for standard molar enthalpy change of formation?

A

The enthalpy change when 1 mole of substance is formed from its elements with all reactants and products in their standard states (298K and 100kPa)

57
Q

What is the definition for stereoisomer?

A

Isomers with the same molecular formula and the same structure, but different position of atoms in space.

58
Q

What is the definition for structural isomer?

A

Isomers with the same molecular formula but a different structure.

59
Q

What is the definition for Triglyceride?

A

An ester formed between glycerol (Propane-1,2,3-triol) and three fatty acid molecules.

60
Q

What is the definition for Specific heat capacity?

A

The amount of heat needed to raise the temperature of 1g of substance by 1 K.

61
Q

What is the definition for van der waals force?

A

A type of intermolecular force of attraction that is caused by instantaneous dipoles and acts between all atoms and molecules.

A Level Chemistry (11 decks)

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