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Z/ HIGHER Chemistry > Definitions > Flashcards

Definitions Flashcards

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1
Q

activated complex

A

an unstable arrangement of atoms formed at the maximum of the potential energy barrier during a reaction

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2
Q

activation energy

A

the energy required by colliding molecules to form an activated complex

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3
Q

addition reaction

A

a reaction in which two or more molecules combine to produce a larger molecule and nothing else

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4
Q

alcohols

A

carbon compounds which contain the hydroxyl -OH functional group

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5
Q

aldehydes

A

carbon compounds which contain the -C=O functional group. they are formed by oxidation of primary alcohols and oxidise to produce carboxylic acids.

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6
Q

alkanes

A

a homologous series of saturated hydrocarbons, general formula CnH2n+2. first member is methane CH4

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7
Q

alkenes

A

a homologous series of unsaturated hydrocarbons, general formula CnH2n. each member contains a carbon to carbon double bond. first member is ethene. CH2=CH2

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8
Q

alkyl group

A

a group of carbon and hydrogen atoms forming a branch in a carbon compound, for example methyl group (CH3-) or ethyl group (C2H5-)

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9
Q

amide link

A

a group of atoms formed by condensation polymerisation of amino acids in the formation of protein chains. the amide link is CONH and occurs between each pair of amino acid residues in the chain. also called a peptide link

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10
Q

amine group

A

a functional group -NH2

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11
Q

amino acids

A

compounds of general formula, H2NCHRCOOH where R is a difference which link by condensation reaction to form proteins.

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12
Q

essential amino acids

A

cannot be synthesised by an organism and must be present in its diet

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13
Q

antioxidants

A

compounds that slow oxidation reactions. they are commonly added to food to prevent edible oils becoming rancid. example include vitamin E and C

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14
Q

atom economy

A

a measure of the proportion of reactants that have been converted into products. it is calculated using formula, atom economy = mass of desired product/total mass of reactants x 100. reactions with a high atom economy are desirable

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15
Q

atomic number

A

numbers of protons in the nucleus of an atom

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16
Q

average rate

A

the change in mass or conc. of a reactant or product divided by time interval during which the change occurs

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17
Q

biodegrade

A

the breakdown of materials by bacteria or other biological means

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18
Q

bonding continuum

A

a concept applied to bonding. ionic and covalent bonding lie at opposite ends with polar covalent bonding in-between on the continuum

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19
Q

carbonyl group

A

C=O. it is present in ketones and aldehydes

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20
Q

catalyst

A

a substance which speeds up a reaction without itself being used up by providing an alternative pathway and it lowers the activation energy

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21
Q

chromatography

A

a technique used for separating substances. molecules of different size or polarity can be separated by this technique which used a mobile phase of gas or liquid passing over a stationary phase of solid or liquid-impregnated solid

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22
Q

closed system

A

reversible reactions will only reach a state of dynamic equilibrium when the reaction takes place in a reaction vessel which prevents reactants and products escaping

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23
Q

collision theory

A

a theory used to explain the factors which lead to a successful collision. they require reactants to i) collide, ii) have correct collision geometry and iii) have sufficient activation energy before a reaction occurs

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24
Q

condensation polymerisation

A

a process whereby many small molecules (monomers) join to form a large molecule (polymer) with water or other small molecules formed at the same time. an example of this is forming a protein form amino acids

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25
Q

condensation reaction

A

a reaction in which two (or more) molecules join together by the elimination of a small molecules, such as water

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26
Q

covalent bonding

A

a bond formed between two atoms by the sharing of a pair of electrons. this usually occurs between non-metal atoms

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27
Q

covalent molecular

A

bonding in various non-metal small molecules like water or chlorine (Cl2)

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28
Q

covalent network

A

a very strong stable structure held together by strong covalent bonds. consequently, the compounds are all solids at room temperature and have very high melting points

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29
Q

covalent radius

A

a useful measure of atomic size, being half the distance between the nuclei of two covalently bonded atoms of an element. covalent bond lengths between any two atoms can be obtained by adding the appropriate covalent bond radii.

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30
Q

cycloalkanes

A

a homologous series of saturated ring molecules with general formula CnH2n. simplest is cyclopropane, C3H6

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31
Q

dehydration

A

the removal of water from a single compound for example dehydration of ethanol C2H5OH produces ethene C2H4.

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32
Q

denaturing/denature

A

altering the shape of a protein by an increase in temperature or a reduction in pH. loss of enzyme activity is a consequence

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33
Q

detergent `

A

a soap-like molecule which can dissolve fats and oils. has -SO3 (sulphonate) group

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34
Q

displacement

A

a redox reaction where a metal high in the electrochemical series reacts with a metal compound lower in the series

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35
Q

distillation

A

a process used for separating liquid mixtures. a liquid is boiled and its vapour then condensed to collect pure samples of the liquid. it is used to increase the percentage of ethanol after fermentation

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36
Q

electrochemical series

A

a list of chemicals arranged in order of their increasing ability to gain electrons, in other words in order of increasing oxidising power

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37
Q

electrolysis

A

the process which occurs when a current of electricity is passed through a molten electrolyte (resulting in decomposition) or an electrolyte solution (resulting in decomposition of the solute and/or the water)

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38
Q

electronegativity

A

the strength of the attraction by an atom of an element for its bonding electrons. if the electronegativities of two atoms sharing electrons are similar the bond will be almost purely covalent. the greater the difference in electronegativities the more likely the bond is to be polar covalent or even ionic

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39
Q

emulsifier

A

a compound which allows oil and water to mix

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40
Q

emulsion

A

a mixture of liquids where small droplets of one liquid are dispersed in another liquid. emulsions of oil and water are commonly found in food

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41
Q

endothermic reaction

A

a reaction where heat energy is absorbed from the surroundings. positive enthalpy change

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42
Q

end-point

A

the point in a titration where the indicator changes colour to indicate the reaction is complete

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43
Q

enthalpy change

A

the difference in heat energy between reactants and products in a reaction

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44
Q

enthalpy of combustion

A

the enthalpy change when one mole of a substance is completely burnt in oxygen

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45
Q

enzyme

A

a globular protein which is able to catalyse a specific reaction

46
Q

equilibrium

A

state attained in a reversible reaction when forward and reverse reactions are taking place at the same time

47
Q

essential oils

A

oils extracted from plants. they have distinctive smells, are non-polar, volatile and contain compounds known as terpenes

48
Q

esters

A

carbon compounds formed when alcohols react with carboxylic acids by condensation

49
Q

exothermic reaction

A

a reaction where heat energy is released to the surroundings. negative enthalpy change

50
Q

fats

A

esters formed from one molecule of glycerol and three molecules of, usually saturated, long chain carboxylic acids. the compounds have melting points high enough to be solid at room temperature.

51
Q

fatty acids

A

carboxylic acids formed from the hydrolysis of fats and oils

52
Q

feedstock

A

a substance derived from a raw material which is used to manufacture another substance

53
Q

fermentation

A

the process catalysed by enzymes in yeast which converts sugars into ethanol and carbon dioxide. this is known as alcoholic fermentation

54
Q

free radicals

A

highly reactive atoms or molecules with unpaired electrons

55
Q

free radical scavenger

A

a compound added to plastics, cosmetics and foods to prevent free radical reactions. these scavengers react with free radicals to produce stable molecules and terminate the reaction

56
Q

gas liquid chromatography (GLC)

A

a technique used to separate mixtures in gas phase

57
Q

glycerol

A

propan-1,2,3-triol; formed form the hydrolysis of fats and oils

58
Q

haber process

A

industrial production of ammonia from nitrogen and hydrogen using high pressure and temperature, with iron as a catalyst

59
Q

hess’s law

A

the enthalpy change of a chemical reaction depends only on the chemical nature and physical state of the reactants and products and is independent of any immediate steps

60
Q

homologous series

A

a group of chemically similar compounds which can be represented by a general formula. physical properties change progressively through the series, for example the alkanes show a steady increase in boiling point

61
Q

hormones

A

chemicals, often complex proteins, which regulate metabolic processes in the body. an example is insulin which regulates sugar metabolism

62
Q

hydration

A

the addition of water to an unsaturated compound, for example the hydration of ethene C2H4 produces ethanol C2H5OH

63
Q

hydrocarbon

A

a compound containing elements carbon and hydrogen only

64
Q

hydrogenation

A

the addition of hydrogen to an unsaturated compound; for example hydrogenation converts alkenes to alkanes and oils into fats

65
Q

hydrogen bonds

A

intermolecular forces of attraction. the molecules must contain highly polar bonds in which hydrogen atoms are linked to very electronegative nitrogen, oxygen or fluorine atoms. The hydrogen atoms are then left with a positive charge and are attracted to the electronegative atoms of other molecules. They are a specific, stronger type of PDPD interaction.

66
Q

hydrolysis

A

the breaking down of larger molecules into smaller molecules by reaction with water

67
Q

hydrophilic

A

parts of a molecule which are attracted to water, for example the -OH group in alcohols

68
Q

hydrophobic

A

parts of a molecule which repel water for example the long hydrocarbon chains in fats and oils

69
Q

hydroxyl group

A

the -OH group; it is found in alcohols

70
Q

intermolecular bonding

A

bonds between molecules such as LDF, PDPF interactions and hydrogen bonds. these are much weaker than intramolecular bonds

71
Q

intramolecular bonding

A

bonds within molecules such as covalent and polar covalent bonds

72
Q

ionic bond

A

bond formed as a result of attraction between positive and negative ions

73
Q

ionisation

A

the loss or gain of electrons by neutral atoms to form ions

74
Q

ionisation energy

A

the energy required to remove 1 mole of electrons from 1 mole of atoms in the gaseous state

75
Q

ions

A

atoms or groups of atoms which possess a positive or negative charge due to loss or gain of electrons

76
Q

isomers

A

compounds which have the same molecular formula but different structural formulae.

77
Q

isotopes

A

atoms of the same element which have different numbers of neutrons. they have the same atomic number but different mass number

78
Q

ketones

A

carbon compounds which contain the carbonyl group (C=O). formed from oxidation of secondary alcohols. cannot be oxidised using mild oxidising agents

79
Q

Le Chatelier’s principle

A

if any change of physical or chemical conditions is imposed on any chemical equilibrium then the equilibrium alters in the direction which tends to counteract the change of conditions

80
Q

London dispersion force

A

a force of attraction between all atoms and molecules formed from temporary and induced dipoles

81
Q

mass number

A

the total number of protons and neutrons in the nucleus of an atom

82
Q

metallic bonding

A

the bonding responsible for typical metallic properties : malleability, ductility and electrical conductivity in metals and alloys. each atom loses its outer electrons to form positive ions. these pack together in a regular crystalline arrangement with the electrons delocalised through the structure, binding the ions together

83
Q

miscibility

A

the ability of liquids to mix perfectly together. in contrast, immiscible liquids form clearly defined layers with the denser liquid being the lower layer

84
Q

mobile phase

A

in chromatography, the moving part of the process; for example the inert gas in GLC which carries the mixture of compounds through the column, or the solvent in paper chromatography which carries the mixture of compounds up the paper

85
Q

molar bond enthalpy

A

the energy required to break one mole of covalent bonds

86
Q

molar volume

A

the volume of one mole of a gas at a specified temperature and pressure

87
Q

monatomic

A

a term used to describe the noble gases that are composed of individual atoms which do not bond to each other. they are held together by LDF in liquid and solids state

88
Q

non-polar covalent bond

A

a covalent bond where both atoms share the electrons equally. this occurs between all elements that exist as molecules (Cl2, S8) since the atoms joining are identical. it also occurs in compounds where the bonding atoms have a small difference in electronegativity such as hydrocarbons

89
Q

oils

A

esters formed from one molecule of glycerol and three molecules of typically unsaturated carboxylic acid. oils have melting points low enough to be liquids at room temperature

90
Q

oxidation

A

a process where electrons are lost

91
Q

oxidising agent

A

a substance which gains electrons or accepts electrons

92
Q

peptide link

A

amide link but in a protein

93
Q

permanent dipole-permanent dipole interactions

A

the attraction between molecules which possess a permanent dipole because of the presence of polar bonds

94
Q

polar covalent bonds

A

bonds formed between non-metallic atoms by sharing a pair of electrons. if the atoms have considerably different electronegativities, the electrons are not shared equally, the more electronegative atom becoming slightly negative in comparison to the other atom.

95
Q

polymer

A

a large molecule which is formed by joining together many smaller molecules (monomers)

96
Q

polymerisation

A

the process where a polymer is formed

97
Q

raw material

A

a useful substance for the chemical industry which found naturally, for example crude oil, water, air, metallic ores, coal, etc. can be made into feedstocks

98
Q

redox reaction

A

a reaction where reduction and oxidation happen at the same time. electrons are lost by one substance and gained by another

99
Q

redox titration

A

an experiment which the volumes of aqueous solutions of a reducing agent and an oxidising agent, which react together completely, is measured accurately.

100
Q

reducing agent

A

a substance which loses electrons or is an electron donor

101
Q

reduction

A

a process where electrons are gained

102
Q

reproducibility

A

results obtained from an experiment are said to be reproducible if the same data can be obtained when the experiment is repeated. an experiment with good reproducibility will produce the same results again and again when carried out

103
Q

retention time

A

the length of time it takes a substance to reach the detector after being injected into the chromatography column

104
Q

rogue data

A

results that are unusual or do not fit pattern of expected results

105
Q

screening

A

the ability of electrons in the inner energy levels to reduce the attraction of the nuclear charge for the electrons of the outermost levels

106
Q

standard solution

A

a solution of a known concentration

107
Q

stationary phase

A

in chromatography it is the phase other than the mobile phase. for example the liquid in GLC

108
Q

temporary dipole

A

formed in all atoms where an excess of electrons is formed at one part of the atom. temporary dipoles are the basis for LDF

109
Q

terpene

A

unsaturated compounds found in many plant oils. they are formed from the joining together of isoprene units

110
Q

triglyceride

A

the molecules found in fats and oils. formed from one glycerol molecule joining to three fatty acid molecules

111
Q

uv light

A

a high energy form of radiation which can break bonds in molecules, causing free radicals to form

112
Q

van der waals’ forces

A

the forces of attraction that occur between all atoms and molecules known as intermolecular forces and include hydrogen bonding, PDPD and LDF. these are much weaker than covalent bonds

Z/ HIGHER Chemistry (25 decks)

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