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Chemistry > Definitions > Flashcards

Definitions Flashcards

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1
Q

Atomic orbital

A

A region in space in which there is a high probability of finding an electron

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2
Q

Relative atomic mass

A

The average of the mass numbers of the isotopes of the element as they occur naturally taking their abundances into account expressed on a scale in which atoms of the carbon-12 isotope have a mass of exactly 12 units

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3
Q

First ionisation energy

A

The minimum energy required to remove the most loosely bound electron from a gaseous atom in the ground state

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4
Q

Oxidation

A

Loss of electrons

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5
Q

Isotope

A

Atoms of the same element that have different mass numbers due to the different number of neutrons in the nucleus

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6
Q

Energy level

A

Fixed amount of energy an electron in an atom can have

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7
Q

Radioactivity

A

The spontaneous breaking up of unstable nuclei with the release of one or more types of radiation

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8
Q

Atomic radius

A

Half the distance between the nuclei of two atoms joined together by a single covalent bond

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9
Q

Heisenberg’s uncertainty principle

A

It is impossible to measure at the same time both the velocity and position of an electron

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10
Q

Alpha particle

A

Helium nucleus

2 protons & 2 neutrons

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11
Q

Principle of mass spectrometry

A

Charged particles moving in a magnetic field are deflected to different extents according to their masses and are this separated according to these masses

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12
Q

Ground state

A

Electrons occupy lowest available energy levels

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13
Q

Excited State

A

Electrons occupy higher energy levels than those available in the ground state

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14
Q

Atomic number

A

Number of protons in the nucleus of the atom

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15
Q

Radioisotope

A

Radioactive isotope

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16
Q

Energy sub-level

A

Sub-division of a main energy level consisting of one or more orbitals of the same energy

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17
Q

Mass number

A

The sum of the number of protons and neutrons in the nucleus of an atom

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18
Q

Half life

A

Time taken for half of the nuclei in a sample to decay

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19
Q

Oxidation number

A

The charge that an atom has or appears to have when electrons are distributed according to certain rules

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20
Q

Second ionisation energy

A

The energy required to remove an electron from an ion with one positive charge in the gaseous state

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21
Q

Reduction

A

When an element gains electrons

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22
Q

Cathode Rays

A

Streams of negatively charged particles called electrons which travel in straight lines from the cathode to the anode, are deflected by electric & magnetic fields and have sufficient energy to move a small object such as a paddle wheel

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23
Q

Element

A

Cannot be broken down into simpler parts

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24
Q

Mendeleev’s periodic law / system

A

When elements are listed according to relative atomic mass, their chemical properties repeat periodically

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25
Q

Modern periodic law / system

A

When elements are listed according to atomic number, their chemical properties repeat periodically

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26
Q

Aufbau principle

A

When building up the electron configuration of an atom in its ground state, the electrons occupy the lowest available energy levels

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27
Q

Daltons atomic theory

A

• All matter is made up of very small particles called atoms
• All atoms are indivisible, they cannot be broken down into simpler particles

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28
Q

Hund’s rule of maximum multiplicity

A

When two or more orbitals of equal energy are available, electrons occupy them singly before filling them in pairs

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29
Q

Law of conservation of matter

A

During a chemical reaction, mass is neither created or destroyed

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30
Q

Newland’s octaves

A

Every eight element has properties similar to the first

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31
Q

Nuclear energy

A

Process that alters the composition, structure or energy of a nucleus

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32
Q

Pauli exclusion principle

A

No more than two electrons may occupy an orbital and they must have opposit spin

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33
Q

Radio carbon dating

A

Dates an object based on C-14 to C-12 ratio

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34
Q

Triad

A

Group of 3 elements with similar chemical properties where the atomic weight of the middle one is approximately equal to the average of the other two

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35
Q

Oxidising agent

A

A substance that brings about oxidation in other substances (is reduced)

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36
Q

Reducing agent

A

A substance that brings about reduction in other substances (is oxidised)

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37
Q

Electronegativity

A

The relative attraction that an atomin a molecule has for the shared pair of electrons in a covalent bond

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38
Q

Pi bond

A

Sideways overlap of p orbitals

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39
Q

Sigma bond

A

Head on overlap of orbitals

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40
Q

Ionic bonding

A

Force of attraction between oppositely charged ions in a compound

41
Q

Polar covalent bond

A

A bond in which there is unequal sharing of the pair (or pairs) of electrons

42
Q

Covalent bond

A

Shares electrons

43
Q

Octet rule

A

When bonding, atoms tend to reach an electron configuration with eight electrons in the outermost energy level

44
Q

Transition metal

A

Forms at least one ion with a partially filled d sublevel

45
Q

Avogadro’s law

A

Equal volumes of gases at the same temperature and pressure have equal number of particles

46
Q

Mole

A

The amount of a substance that contains 6 x10^23 particles of that substance

47
Q

Charles law

A

At constant pressure, the volume of a fixed mass of gas is directly proportional to its temperature measured on the Kelvin scale

48
Q

Ideal gas

A

One that perfectly obeys all the assumptions of the kinetic theory of gases under all conditions of temperature and pressure

49
Q

Gay-Lussac’s law

A

The volume of reacting gasses and the volumes of any gaseous products are in the ratio of small whole numbers provided they are measured at the same temperature and pressure

50
Q

Boyle’s law

A

At constant temperature, the volume of a fixed mass of gas is inversely proportional to its pressure

51
Q

Brønsted-Lowry → acid

A

Proton donor

52
Q

Brønsted-Lowry → base

A

Proton acceptor

53
Q

Brønsted-Lowry → conjugate acid base pair

A

An acid and a base that differ by one proton

54
Q

Arrhenius → acid

A

A substance that dissociates in water to produce H+ ions

55
Q

Arrhenius → base

A

A substance that dissociates in water to produce OH- ions

56
Q

Primary standard

A

A substance that can be obtained in a stable, pure and soluble solid form so that it can be weighed out and dissolved in water to give a solution of accurately known concentration

57
Q

Standard solution

A

A solution of known concentration (molarity)

58
Q

Titration

A

A laboratory procedure in which a measured volume of one solution is added to a known volume of another solution until the reaction is complete

59
Q

Heat of combustion

A

The heat change when one mole of a substance is burned completely in excess oxygen

60
Q

Octane number

A

The measure of a fuels ability to resist knocking

61
Q

Structural isomers

A

Compounds of the same molecular formula with different structural formulas

62
Q

Unsaturated

A

Compounds with double or triple bonds present between carbon molecules

63
Q

Homologous series

A

A series of compounds of similar chemical properties, showing gradations in physical properties, having a general formula for its members and each member differing from the previous member by a CH2 unit

64
Q

Bond energy

A

Average energy required to break one mole of a particular bond into separate atoms in the gaseous state

65
Q

Catalytic cracking

A

Splitting of long chain moleculesby heat and catalysts

66
Q

Heat of formation

A

Heat change when one mole ofa a compound is formed by its elements in their standard states

67
Q

Heat of reaction

A

Heat change when the number of moles of reactants in the balanced equation react completely

68
Q

Hydrocarbon

A

Compounds of Carbon and hydrogen

69
Q

Auto-ignition / knocking / pinking

A

The premature ignition of the petrol-air mixture before normal ignition of the mixture by a spark

70
Q

Isomerisation

A

Changing straight chain alkanes into their isomers

71
Q

Saturated

A

Only single bonds between carbon molecules

72
Q

Fractionation

A

Separation of components by their boiling points

73
Q

Heat of neutralisation

A

Heat change when one mole of hydrogen from acid reacts with one mole of hydroxide ions from a base

74
Q

Rate of achemical reaction

A

Change in concentration per unit time of any one reactant or product

75
Q

Activation energy

A

Minimum energy colliding particles must have for a reaction to occur

76
Q

Heterogenous catalysis

A

Reactants and the catalyst are in different phases

77
Q

Catalyst

A

A substance that alters the rate of a chemical reaction but is not used up in the reaction

78
Q

Effective collision

A

One that results in the formation of products

79
Q

Autocatalysis

A

One of the products of the reaction acts as a catalyst for the reaction

80
Q

Homogenous catalysis

A

Both the reactants and the catalyst are in the same phase

81
Q

Enzyme

A

Biological catalyst

82
Q

Catalytic converter

A

A device in the exhaust system of a motor vehicle which contains catalysts to convert pollutants in the exhaust gases to less harmful substances

83
Q

Catalyst poison

A

A substance that makes a catalyst inactive

84
Q

Emulsion

A

Oil droplets in water

85
Q

Primary alcohol

A

One carbon atom attached to the carbon to which the OH group is attached

86
Q

Secondary alcohol

A

Two carbon atoms attached to the carbon to which the OH group is attached

87
Q

Tertiary alcohol

A

Three carbon atoms attached to the carbon to which the OH group is attached

88
Q

Le Chatelier’s principle

A

If a stress is applied to a system at equilibrium, the system readjusts to receive the stress applied

89
Q

Chemical equilibrium

A

A state of dynamic balance in a reversible reaction where the rate of the forward reaction is the same as the rate of the backward reaction

90
Q

Dynamic state

A

Reactants ave continuously forming products and the products are continuously forming reactants

91
Q

pH

A

negative log to the base 10 of hydrogen ions, where square brackets indicate moles per litre

92
Q

Secondary treatment (of sewage)

A

Biological oxidation

93
Q

Biochemical oxygen demand (BOD)

A

The amount of dissolved oxygen consumed by biological action when a sample of water is kept at 20°c in the dark for five days

94
Q

Tertiary treatment (of sewage)

A

Removal of nitrogen and phosphorous compounds

95
Q

Hard water

A

Water that will not easily form a lather with soap

96
Q

Flocculation

A

The coming together of small suspended particles in water

97
Q

Eutrophication

A

The enrichment of water with nutrients, leading to excessive growth of algae and other plants

98
Q

Primary treatment (of sewage)

A

Removal of solids by screening and settlement

Chemistry (22 decks)

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