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AS & AL Chemistry Vocab > AS Vocabulary > Flashcards

Flashcards in AS Vocabulary Deck (166):
1

alkali

a base that is soluble in water

2

acid

a proton (hydrogen ion) donor

3

active site

the "pocket" on an enzyme surface where the substrate binds and undergoes catalytic reaction

4

allotrope

different crystalline or molecular forms of the same element. Graphite and diamond are allotropes of carbon

5

alloy

a misture of two or more metals or a metal with a non-metal

6

amphoteric

able to behave as both an acid and a base. e.g.aluminium oxide

7

atomic orbitals

regions of space outside the nucleus that can be occupied by one or, at most, two electron. orbitals are named s, p, d and f. they have different shapes

8

average bond energy

a general bond energy value used for a particular bond, e.g. a C-H, when the exact bond energy is not required. average bond energies are often used because the strength of a bond between two particular types of atom is slightly different in defferent compounds

9

Avogadro constant

the number of atoms ions molecules or electrons in a mole of atoms ions molecules or electrons. its numerical value is 6.02*10^23

10

base

a proton (hydrogen ions) acceptor

11

boiling point

the temperature at which the vapour pressure is equal to the atmospheric pressure

12

Boltzmann distribution

a graph showing the distribution of energies of the particles in a sample given temperature

13

bond energy/bond enthalpy

the energy needed to break 1 mole of a particular bond in 1 mole of gaseous molecules

14

Bronsted-Lowry theory of acids

acids are proton donors and bases are proton acceptors

15

catalyst

a substance that increases the rate of a reaction but remains chemically unchangeditself at he end of the reaction

16

closed system

a system in which matter or energy is not lost or gained, e.g. gases in a closed vessel

17

compound

a substance made up of two or more elements bonded together

18

condensation

the change in state when a vapour changes to a liquid

19

conjugate pair (acid/base)

an acid and base on each side of an equilibrium equation that are related to each other by the difference of exactly one proton; e.g. the acid in the forward reaction and the base in the reverse reaction or the base in the forward reaction and the acid in the backward reaction

20

co-ordinate bond/dative covalent bond

a covalent bond in which both electrons in the ond come from the same atom

21

covalent bond

a bond formed by the sharing of pairs of electrons between two atoms

22

degenerate orbitals

atomic orbitals at the same energy level

23

delocalised electrons

electrons that are not associated with a particular atom - they can move between tree or more adjacent atoms

24

denaturation

the process by which the three-dimensional structureof a protein or other biological macromolecule is change, often irreverisbly. relatively high temperature, extremes of pH and organic solvents often cause denaturation

25

dipole

a separation of charge in a molecule. one end of the molecule is permanently positively charged and the other is negatively charged

26

displayed formula

a drawing of a molecule that shows all the atoms and bonds within the molecule

27

dissociation

the break-up of a molecule into ions, for example when HCl molecules dissolve in aqueous solution, they dissociate completely into H+ and Cl- ions

28

dot-and-cross diagram

a diagram showing the arrangement of the outer-shell electrons in an ionic or covalent element or compound. the electrons are shown as dots or crosses to show their origin

29

double covalent bond

two shared pairs of electrons bonding two atoms together

30

dynamic equilibrium

in an equilibrium mixture, molecules of reactants are being converted to products at the same rate as products are being converted to reactants

31

electron

tiny subatomic particles found in orbitals around the nucleus. they have a negative charge but have negligible mass

32

electronegativity

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

33

electronic configuartion

a way of representing the arrangement of the electrons in atoms showing the principal quantum shells, the subshells and the number of electrons present, e.g. 1s22s22p3. the electrons may also be shown in boxes

34

electrovalent bond/ionic bond

the elctrostativ attraction between oppositely charged ions

35

element

a substance made of only one type of atom

36

empirical formula

the formula that tells us the simplest ratioo of the different atoms present in a molecule

37

endothermic

term used to describe a reaction in which energy is absorbed from the surroundings: the enthalpy change is positive

38

energy levels (of electrons)

the regions at various distances from the nucleus in which electrons have a particular amount of energy. electrons further from the nucleus have more energy.

39

enthalpy change of atomisation

the enthalpy change when 1 mole of gaseous atoms is formed from its element under standard conditions

40

enthalpy change of hydration

the enthalpy change when 1 mole of a specified gaseous ion dissolves in sufficient water to form a very dilute solution

41

enthalpy chane of solution

the enthalpy change when 1 mole of an ionic solid dissolves in sufficient water to form a very dilute solution

42

enthalpy change

the energy transferred in a chemical reaction. delta h

43

enthalpy cycle

a diagram showing alternative routes between reactants and products that allows the determination of one enthalpy change from other known enthalpy changs by using Hess's law

44

enthalpy profile diagram

a diagram showing the enthalpy change from reactants to products along the reaction pathway

45

enzyme

a protein molecule that is a biological catalyst. most act on a specific substrate

46

enzyme activity

measure of the rate at which substrate is converted to product in an enzyme-catalysed reaction

47

equilibrium constant

a constant calculated from the equilibrium expression for a reaction

48

equilibrium expression

a simple relationship that links Kc to the equilibrium concentrations of reactants and products and the storchiometric equation

49

equilibrium reaction

a reaction that does not go to completion and in which reactants and products are present in fixe concentration ratios

50

exothermic

a reaction in which energy is released to the surrounding: negative enthalpy change

51

fragmentation

the breading up of a molecule into smaller parts by the breading of covalent bonds in a mass spectrometer

52

general/ideal gas equation

an equation relating the volme of a gas to the temperature, pressure and number of moles of gas. ideal gas equation. pV=nRT

53

half-equation

in a redox reaction, an equation showing either an oxidation or a reduction

54

Hess's law

the total enthalpy change for a chemical reaction is independent of the route by which the reaction takes place

55

heterogeneous catalysis

the type of catalysis in which the catalyst is in a different phase from the reactants. e.g. iron in Haber process

56

homogeneous catalysis

catalyst and reactants are in the same phase. e.g. sulfuric acid catalysing the formation of an ester from an alcohol and carboxylic acid

57

hybridisation of atomic orbitals

the proces of mixing atomic orbitals so that each has some character of each of the orbitals mixed

58

hydrogen bond

the strongest type of intermolecular force - it is formed between melecules having a hydrogen atom bonded to one of the most electronegative elements (F, O or N)

59

ideal gas

a gas whose volume varies in proportion to the temperature and in inverse proportion to the pressure.noble gases such as He and Ne approach ideal behaviour because of their low intermolecular forces.

60

intermolecular forces

the weak forces between molecules

61

ionisation energy, deltaHi

the energy needed to remove 1 mole of electrons from 1 of atoms of an element in the gaseous state to form 1 mole of gaseous ions

62

isotopes

atoms of an element with the same number of protons but different numbers of neutrons

63

kinetic theory

the theory that particles in gases and liquids are in constant movement. used to explain the effect of temperature and pressure on the volume of a gas as well as rates of chemical reactions

64

lattice

a regularly repeating arrangement of ions, atoms or molecules in 3D

65

le Chetelier's principle

when any of the conditions affecting the position of equilibrium are changed, the position of that equilibrium shifts to minimise the change

66

lone pairs (of electrons)

pairs of electrons in the outer shell of an atom that are not bonded

67

mass number/nucleon number

number of protons + number of neutrons

68

molar mass

the mass of a mole of substance in grams

69

mass spectrometer

an instrument for finding the relevant isotopic abundance of elements and to help identify unknow organic compounds

70

mole

the unit of amount of substance. the amount of substance that has the same number of particles (atoms, ions, molecules or electrons) as there are atoms in exactly 12g of the carbon-12 isotope

71

molecular formula

the formula that tells us the actual numbers of each type of atom in a molecule

72

neutron

a subatomic particle found in the nuvleus of an atom. it has no charge and has the same mass as a proton

73

non-polar

a molecule with no separation of charge; it will not be attracted to a positive or negative charge

74

nucleus

small dense core at the centre of every atom, containing protons (+1) and neutrons (0). always +

75

open system

a system in which matter is lost or gained. e.g. a mixture of solids and gases in an open beaker

76

oxidation

addition of oxygen, removal of electrons or increase in oxidation number of a substance; organic - reaction whcih oxygen atoms are added to a molecule/hydrogen atoms are removed

77

oxidation number/state

a number given to an atom in a compound that describes how oxidised or reduced it is

78

oxidising agent

reactant that increase the oxidation # or removes e- from another reactant, reduced itself

79

partial pressure

pressure that an individual gas contributes to the overall pressure in a mixture of gases

80

permanent dipole-dipole force

type of intermolecular force between molecules that have permanent dipoles

81

pi bound

multiple covalent bond involving the sideways overlaping of p atomic orbitals

82

polar (covalent bond)

covalent bond in which the two bonding electrons are not shared equally by the atoms in the bond. the atom with the greater share of the electrons have a partial negative charge, delta-, and the other has a partial positive charge, delta+

83

principal quantum shells, n

regions at various distances from the nucleus that may contain up to a certain number of electrons. 1st quantum shell contains up to 2 e- and 2nd up to 8 and 3rd up to 18. 2n^2

84

proton

positively charged subatomic particle in the nucleus

85

rate of reaction

a measure of the rate at which reactants are used up or the rate at which products are formed. in moldm-3s-1

86

real gases

gases that do not obey the ideal gas law, espacially at low temperature and high pressure

87

redox reaction

a reation in which oxidation and reduction take place at the same time

88

reducing agent

reactant that decreases the oxidation number of or + e- to another reactant

89

relative formula mass

mass of one formula unit of a compound measured on a scale on which an atom of the carbon-12 isotope has a mass of exactly 12 units

90

relative isotopic mass

mass of a particular isotope of an element on a scale in which an atom of the carbon-12 isotope has a mass of exactly 12 units

91

relative molecular mass

mass of a molecule measured on a scale in which an atom of carbon-12 isotope has a mass of exactly 12 units

92

reversible reaction

reaction in which products can be changed back to reactants by reversing the conditions

93

shielding

the ability of innershells of electrons to reduce the effective nuclear charge on electrons in the outer shell

94

sigma bonds

single covalent bonds, formed by the 'end-on' overlap of atomic orbitals

95

specific

most enzymes are described as specific because they will only catalyse one reaction involving one particular molecule or pair of melecules

96

spectator ion

ion present in a reaction mixture that od not take part in the reaction

97

spin-pair repulsion

electrons repel each other as they have the same charge. electrons arrange themselves so that they first singly occupy different orbitals in the same sublevel.after that they pair up with their spins opposed to each other

98

standard condition

10^5 pascals (100 kPa), 298K (25 degree). used to compare moles of gases or enthalpy changes accurately

99

standard enthalpy change

an enthalpy change that takes place under standard conditions of pressure and temperature

100

state symbol

s, l, g, aq

101

stoichiometry

the mole ratio of the reactants and products in the balanced equation for a reaction

102

strong acid/base

an acid or base that is completely ionised in water

103

subshell

region within the principal quantum shells where electrons have more or less energy depending on their distance from the nucleus. s, p, d, f

104

substrate

a molecule that fits into the active site of an enzyme and reacts

105

successive ionisation energy, deltaHi1, deltaHi2

energy required to remove the first, second, third electrons and so no from a gaseous atom or ion, producing an ion with one more positive charge each time. in kJ per mole of ions produced

106

surrounding

in enthalpy changes, anything other than the chemical reactants and products, for example the solvent, the test tube in which the reaction takes place, the air around the test tube

107

titre

in a titration, the final burette reading minus the initial burette reading

108

triple covalent bond

3 shared pairs of e- bonding 2 atoms together

109

van der Waal's force

the weak forces of attraction between molecules caused by the formation of temporary dipoles

110

vaporisation

the change in stae when a liquid changes to vapour

111

vapour pressure

pressure exerted by a vapour in equilibrium with a liquid

112

weak acid/base

an acid or base that is only slightly ionised in water

113

acyl chloride

a reactive organic compound related to a carboxylic acid, with the OH group in the acid replaced by a Cl atom, for example ethanoyl chloride, CH3COCl

114

addition polymeristation

the reaction is which monomers containing carbon-to-carbon double bonds react together to form long-chain molecules called polymers

115

addition reaction

an organic reaction in which two reactant molecules combine to give a single product molecule

116

alkaline earth metals

the elements in Group 2 of the Periodic Table

117

alkanes

saturatedhydrocarbons with the general formula CnH2n+2

118

alkenes

unsaturated hydrocarbons with a carbon-carbon double bond. Their general formula is CnH2n

119

anion

a negatively charged ion

120

biofuels

renewable fuels, soured from plant or animal materials

121

carbocation

an alkyl group carrying a single positive charge on one of its carbon atoms, e.g. +CH2CH3

122

cation

a positively charged ion

123

chiral centre

a carbon atom with four different groups attached, creating the possibility of optical isomers

124

condensation reaction

a reaction in which two organic molecules join together and in the process eliminate a small molecule, such as water or hydrogen chloride

125

cracking

the process in which large, less useful hydrocarbon molecules are broken down into smaller, more useful molecules

126

dehydration

a reaction in which a water molecule is removed from a molecule, e.g. in the dehydration of an alcohol to give an alkene

127

disproportionation

the simultaneous reduction and oxidation of the same species in a chemical reaction

128

electrophile

a species that can act as an acceptor of a pair of electrons in an organic mechanism

129

elimination

a reaction in which a small molecule, such as H2O or HCl, is removed from an organic molecule

130

enhanced global warming

the increase in average temperatures around the world as a consequence of the huge increase in the amounts of CO2 and other greenhouse gases produced by human activity

131

esterification

the reaction between an alcohol and a carboxylic acid (or acyl chloride) to produce an ester and water

132

eutrophication

an environmental problem caused by fertilisers leached from fields into rivers and lakes. the fertiliser then promotes the growth of algae on the surface of water. when the algae die, bacteria thrive and use up the dissolved oxygen in the water, killing aquatic life

133

Fehling's solution

an alkaline solution containing copper(II) ions used to distinguish between aldehydes and ketones. a positive test is one in which the clear blue solution gives a red/orange precipitate when warmed with aldehydes, but no change is observed with ketones

134

free radical

very reactive atom or molecule that has a single unpaired electron

135

free-radical substitution

the reaction in which halogen atoms substitude for hydrogen atoms in alkanes. the mechanism involves steps in which reactive free radicals are produced (initiation), regenerated (propagation) and consumed (termination)

136

functional group

an atom or group of atoms in an organic molecule that determine the characteristic reactions of a homologous series

137

general formula

a formula that represents a homologous series of compounds using letters and numbers;e.g. the general formula for alkanes is CnH2n+2. by substituting a number for n in the general formula you get the molecular formula of a particular compound in that homologous series

138

giant molecular structure / giant covalent structure

structures having a three-dimensional network of covalent bonds throughout the whole structure

139

haglogens

group 17 elements

140

hydrocarbon

a compound made up of carbon and hydrogen only

141

hydrolysis

the breakdown of a compound by water, which is often speeded up by reacting with acid or alkali

142

hydroxynitrile

an organic compound containing both an OH and a CN group, e.g. 2-hydroxypropaneitrile, CH3CH(OH)CN

143

infra-red spectroscopy

a technique for identifying compounds based on the change in vibrations of particular atoms when infra-red radiation of specific frequencies is absorbed

144

initiation step

the first step in the mechanism of free-radical substitution of alkanes by halogens. it involves the breaking of the halogen-halogen bond by UV light from the Sun

145

metalloid

elements that have a low electrical conductivity at room temperature but whose conductivity increases with increasing temperature. ________ are found in a diagonal band running from the top left to nearly the bottom right of the p-block in the Periodic Table

146

monomer

a small, reactive molecule that reacts to make long-chain molecules called polymers

147

nanotechnology

the design and production of machines that are so small we measure them in nanometres (nm), where 1 nm = 1*10^-19 m

148

nucleophile

species that can act as a donor of a pair of electrons

149

nucleophilic addition

the mechanism of the reaction in which a nucleophile attacks the carbon atom in a carbonyl group and adds across the C=O bond,e.g. aldehydes or ketones reacting with hydrogen cyanide

150

optical isomers

stereoisomers that exist as two non-superimposable mirror images

151

periodicity

the repeating patterns in the physical and chemiscal properties of the elements across the periods of the Periodic Table

152

polymer

a long-chain molecule made up of many repeating units

153

primary alcohol

an alcohol in which the carbon atom bonded to the OH group is attached to one other carbon atom (or alkyl group)

154

propagation step

a step in a free radical mechanism in which the radicals formed can then attack reactant molecules generating more free-radicals, and so on.

155

secondary alcohol

an alcohol in which the carbon atom bonded to the OH group is attached to two other carbon atoms (or alkyl group)

156

saturated hydrocarbons

compounds of hydrogen and carbon only in which the carbon-carbon bonds are all single covalent bonds, resulting in the maximum number of hydrogen atoms in their molecules.

157

Sn1 mechanism

the steps in a nucleophilic substitution reaction in which the rate of the reaction (which is determined by the slow step in the mechanism) involves only the organic reactant, e.g. in hydrolysis of a tertiary halogenoalkane

158

Sn2 mechanism

the steps in a nucleophilic substitution reaction in which the rate of the reaction (which is determined by the slow step in the mechanism) involves two reacting species, e.g. in the hydrolysis of a primary halogenoalkane

159

solute

a substance that is dissolved in a solution

160

stereoisomers

compounds whose molecules have the same atoms bonded to each other (same structural formular) but with different arrangement of atoms in space

161

structural isomers

compounds with the same molecular formula but different structural formulae

162

substitution

a reaction that involves the replacement of one atom, or group of atoms, by another

163

termination step

the final step in a free-radical mechanism in which two free radicals react together to form a molecule

164

tertiary alcohol

an alcohol in which the carbon atom bonded to the OH group is attached to three other carbon atoms (or alkyl group)

165

Tollen's reagent

an aqueous solution of silver nitrate in excess ammonia solution, sometimes called ammoniacal silver nitrate solution. it is used to distinguish between aldehydes and ketones. it gives a positive 'silver mirror'test when warmed with aldehydes, but no change is observed with ketones

166

unsaturated hydrocarbons

compounds of hydrogen and carbon only whose molecules contain carbon-carbon double bonds (or triple bonds)