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Chemistry > Definitions > Flashcards

Definitions Flashcards

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1
Q

boiling point

A

The temperature at which the pressure of the gas created above a liquid equals atmospheric pressure

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2
Q

condensation

A

the change of a gas into a liquid. this process is accompanied by the evolution of heat

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3
Q

diffusion

A

the process by which different substances mix as a result of the random motions of their particles

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4
Q

evaporation

A

a process occuring at the surface of a liquid involving the change of state of a liquid into a gas at a temperature below the boiling point. when a solution is heated, the solvent evaporates and leaves the solute behind.

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5
Q

freezing point

A

the temperature at which a substance freezes. this has the same value as the melting point

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6
Q

melting point

A

the temperature at which a solid begins to turn into a liquid. pure substances have a sharp melting point

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7
Q

anion

A

A negative ion. anions are attracted to the anode in electrolysis

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8
Q

atom

A

the smallest part of an element that can exist as a stable entity. it has a central nucleus containing neutrons and protons surrounded by electrons in shells. An atom contains equal numbers of protons and electrons

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9
Q

cation

A

a positive ion. cations are attracted to the cathode in electrolysis

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10
Q

chemical change

A

a permanent change in which a new substance is formed

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11
Q

compound

A

a substance formed by the chemical combination of two or more elements in fixed proportions.

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12
Q

diatomic molecule

A

a molecule containing two atoms

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13
Q

element

A

a substance that cannot be further divided into simpler substances by chemical methods.

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14
Q

ion

A

an atom or group of atoms that has either lost one or more electrons, making it positively charged or gained one or more electrons making it negatively charged.

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15
Q

isotopes

A

different atoms of the same element that have the same number or protons but different number of neutrons

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16
Q

Mass number (nucleon number)

A

the total number of protons and neutrons found in the nucleus of an atom, symbol A

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17
Q

mixture

A

two or more substances mixed together that can be separated by physical means

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18
Q

molecule

A

a group of atoms covalently bonded together

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19
Q

monatomic molecule

A

a molecule which exists of only one atom

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20
Q

oxidation

A

gain of oxygen or loss of electrons or increase in oxidation state

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21
Q

oxidising agent

A

a substance that oxidises another substance and is itself reduced

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22
Q

proton number ( atomic number)

A

the number of protons in the nucleus of an atom, symbol Z

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23
Q

redox reaction

A

a reaction which involves simultaneous oxidation and reduction.

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24
Q

reducing agent

A

a substance that reduces another substance and is itself oxidised.

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25
Q

reduction

A

loss of oxygen or gain or electrons or decrease in oxidation number

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26
Q

relative atomic mass (Ar)

A

the average mass of the isotopes of an element compared to 1/12 of the mass of an atom of 12C

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27
Q

Covalent bond

A

a chemical bond formed by the sharing of one or more pairs of electrons between two atoms

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28
Q

delocalised electrons

A

electrons that are spread out within a metal structure. the electrons are not attached to any one particular ion

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29
Q

giant ionic lattice

A

a regular arrangement of positive and negative ions held together by the electrostatic forces of attraction between ions

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30
Q

intermolecular force

A

a weak force of attraction between simple molecules

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31
Q

ionic bond

A

a strong electrostatic force of attraction between oppositely charged ions

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32
Q

lattice

A

a regular arrangement of atoms, molecules or ions in a solid

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33
Q

avogadro constant

A

6.02 x 10^23 the number of atoms, ions or molecules in one mole of a substance

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34
Q

empirical formula

A

a formula showing the simplest whole number ratio of atoms or ions present in a compound

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35
Q

molar mass

A

the mass of one mole of a compound. unit of g/mol

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36
Q

mole

A

the amount of substance which contains 6.02 x 10^23 atoms, ions or molecules

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37
Q

molecular formula

A

a formula showing the actual number and type of different atoms of each element present in one molecule of compound

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38
Q

relative formula mass Mr

A

the sum of the relative atomic masses of those elements shown in the formula of any substance

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39
Q

anode

A

the positive electrode. it is positively charged because electrons are drawn away from it

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40
Q

binary compound

A

a compound containing two elements chemically combined

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41
Q

cathode

A

the negative electrode. it is negatively charged because an excess of electrons move towards it

42
Q

electrodes

A

the conducting rods by which electric current enters and leaves the electrolyte

43
Q

electrolysis

A

the decomposition of an ionic compound, when molten or in aqueous solution, by the passage of an electric current.

44
Q

electrolyte

A

a liquid which will carry electric current and is chemically charged by it

45
Q

inert electrode

A

an electrode that does not react with the electrolyte or the products of electrolysis. examples are carbon (graphite) and platinum

46
Q

activation energy

A

Ea, is the minimum energy that colliding particles must have in order to react

47
Q

bond energy

A

amount of energy required to break one mole of covalent bonds in gaseous molecules

48
Q

endothermic reaction

A

absorbs thermal energy from the surroundings leading to a decrease in temperature of surroundings

49
Q

enthalpy change

A

the transfer or thermal energy during a reaction is called the enthalpy change, delta H, for the reaction. is negative for exothermic reactions and positive for endothermic reactions

50
Q

exothermic reaction

A

transfers thermal energy to the surroundings leading to an increase in temperature of the surroundings.

51
Q

fossil fuels

A

fuels, such as coal, petroleum and natural gas, formed from the remains of plants and animals

52
Q

fuel

A

a substance that can be conveniently used as a source of energy

53
Q

oil refining

A

the process of converting petroleum into seperate fractions

54
Q

catalyst

A

a substance which increases the rate of a chemical reaction and is chemically unchanged at the end of the reaction. a catalyst increases the rate of a chemical reaction by providing an alternative reaction path which has a lower activation energy

55
Q

enzyme

A

enzymes are protein molecules which are biological catalysts

56
Q

rate of reaction

A

a measure of the change which happens during a reaction in a single unit of time

57
Q

reversible reaction

A

a chemical reaction that can go both forwards and backwards. once some of the products have been formed, they will undergo a chemical change once more to re-form the reactants

58
Q

acid

A

a substance which dissolves in water, producing H+(aq) ions as the only positive ion. a proton donor.

59
Q

alkali

A

a soluble base which produces OH- (aq) ions in water

60
Q

anhydrous salt

A

a salt which has has its water of crystallisation removed

61
Q

base

A

a substance which neutralises an acid, producing a salt and water as the only products. bases are oxides or hydroxides of metals. a proton acceptor

62
Q

indicator

A

a substance that shows whether a substance is acidic or alkaline by changing colour

63
Q

neutralisation

A

the process in which an acid reacts with a base to form water

64
Q

pH scale

A

a scale running from 0 to 14 used express the acidity or alkalinity of a substance

65
Q

saturated solution

A

a solution containing the maximum amount of dissolved solute in the solvent at a given temperature

66
Q

water of crystallisation

A

water incorporated into the structure of a substance as it crystallises. e.g copper (II) sulfate pentahydrate

67
Q

alkali metals

A

the six metallic elements in group 1 of the periodic table

68
Q

electronic configuration

A

a shorthand method of describing the arrangement of electrons within each the electron shells of an atom

69
Q

group (periodic table)

A

a vertical column of elements in the periodic table containing elements with the same number of electrons in their outer shell.

70
Q

halogens

A

the elements found in group VII of the periodic table

71
Q

noble gases

A

the elements in group VIII of the periodic table

72
Q

periodic table

A

a table of elements arranged in order of increasing proton number

73
Q

periods

A

the horizontal rows of elements in the periodic table . the atoms of elements in a period have the same number of occupied shells.

74
Q

transition elements

A

the elements found in the centre of the periodic table between group II and III

75
Q

alloy

A

a mixture of two or more metals or of a metal with a non metal

76
Q

corrosion

A

the process that takes place when metals and alloys are chemically attacked by oxygen, water or any other substance found in their immediate environment

77
Q

metals

A

a class of chemical elements which have a characteristic lustrous appearance and are good conductors of heat and electricity

78
Q

rust

A

an orange-brown layer of hydrated iron (III) oxide found on the surface of iron and steel

79
Q

sacrificial protection

A

a method of rust prevention in which a layer of more reactive metal is applied to the surface of iron or steel

80
Q

catalytic converter

A

a device of converting pollutant exhaust gases from cars into less harmful emissions

81
Q

fertiliser

A

a chemical substance added to soil to replace mineral salts to make plants grow more healthily

82
Q

photosynthesis

A

the process by which green plants synthesise carbohydrates from carbon dioxide and water using light as the energy source and chlorophyll as the catalyst

83
Q

pollution

A

the modification of the environment by human influence

84
Q

addition reaction

A

a reaction in which an atom or group of atoms is added across a carbon-carbon double bond. in an addition reaction only one product is formed/

85
Q

alkane

A

a saturated hydrocarbon that contains single bonds only

86
Q

alkene

A

an unsaturated hydrocarbon in which there is at least one carbon-carbon double bond

87
Q

displayed formula

A

a formula showing all the atoms and bonds in one molecule of a compound

88
Q

functional group

A

the atom or group of atoms responsible for the characteristic reactions of a compound

89
Q

homologous series

A

a family of similar compounds with similar chemical properties and the same functional group and general formula that display a trend in physical properties. Each member differs from the rest by a -CH2- unit

90
Q

hydrocarbon

A

a compound made of molecules containing carbon atoms and hydrogen atoms only

91
Q

monomer

A

a simple molecule that can be polymerised

92
Q

polymer

A

a substance possessing very large molecules consisting of repeated units

93
Q

saturated hydrocarbon

A

a formula showing how groups of atoms are arranged in a molecule

94
Q

structural isomer

A

the existence of compounds with the same molecular formula but different structural formulae

95
Q

substitution reaction

A

a reaction in which an atom or group of atoms is replaced by another atom or group of atoms

96
Q

unsaturated hydrocarbon

A

a hydrocarbon in which there is at least one carbon-carbon double or triple bond

97
Q

combustion

A

a chemical reaction in which a substance reacts rapidly with oxygen, producing heat and light

98
Q

condensation polymer

A

a polymer formed by a condensation reaction ( a reaction in which a simple molecule, such as water, is produced during polymerisation).

99
Q

fermentation

A

a series of biological reactions, catalysed by the enzymes in yeast.

100
Q

functional group

A

an atom or group of atoms responsible for the characteristic chemical reactions of an organic compound

Chemistry (6 decks)

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