Keywords

Question 1

accuracy

Answer 1

A set of measurements is accurate if there is only a small systematic uncertainty associated with them. A systematic uncertainty is due to a systematic error which affects each measurement taken in the same way. A representation of the degree of similarity between the true value of a given parameter and a measurement of that parameter.

Question 2

exponent

Answer 2

also known as the index of power, an expoent is a symbol or number placed above and after another symbol or number to denote the power to which the latter is to be raised.

Question 3

magnitude

Answer 3

the numerical value of a quantity. magnitude does not take account of any direction associated with the quantity or of whether the quantity has a positive or negative value.

Question 4

order of magnitude

Answer 4

the approximate value of a numerical quantity expressed as the nearest power of ten.

Question 5

power of 10

Answer 5

A notation for representing a number as a larger or a smaller number multiplied by a power of ten. For example, in powers of ten notation, 1.234 can be written as 1.234 × 10^3 or 12.34 × 10^2 or 0.123 4 × 10^4 or 123 400 × 10^−2. When the decimal number is below 10, but greater than or equal to 1, for example, 1.234 × 10^3, then this is also known as scientific notation.

Question 6

precision

Answer 6

a measurement has a high precision if the random uncertainty associated with it is small. a series of high precision measurements will only show a small scatter; low precision measurements will show a larger scatter in the measured values.

Question 7

prefixes (for units)

Answer 7

a unit prefix is a specifier that immediately precedes and is joined to units of measurement to indicate multiples or fractions of the units, eg kilometre, 100 metres.

Question 8

scale

Answer 8

a set of divisions used for measurements, as on a ruler. scales are used on the axes of a graph to allow data to be plotted at points corresponding to specific values. for example each cm of the scale on the axis may represent one year, or ten degrees.

Question 9

scientific notation

Answer 9

A notation that represents any number by expressing it as a number equal to or greater than 1, but less than 10, multiplied by a power of ten. Thus 1.30 × 10^3 is in scientific notation (because 1.3 is between 1 and 10), but 0.130 × 10^4 and 13.0 × 10^2 are not.

Question 10

significant figures

Answer 10

Uncertainties in measurements mean that measured values should be quoted only with a certain number of digits, and this number of digits is known as the number of significant figures. For example, 10.2 cm is quoted to three significant figures (abbreviated to 3 sig figs) and this means that there is some uncertainty in the final digit (perhaps the value is 10.3 cm or 10.1 cm) but the other two digits are certain. The larger the number of significant figures quoted for a value, the smaller is the uncertainty in that value

Question 11

si units

Answer 11

An abbreviation for the Système Internationale d’Unités (International System of Units). SI units are used by scientists all over the world to make measurements according to agreed standards. Examples of SI units are the kilogram for mass, the metre for length, and the second for time.

Question 12

bed

Answer 12

a layer of sedimentary rock within the earth’s crust (the plural, beds, is synonymous with strata)

Question 13

bedload

Answer 13

sedimentary grains that are transported by rolling along the bed of a river etc by flowing water or air.

Question 14

cementation

Answer 14

the process of mineral growth in the spaces between the grains of a sediment or sedimentary rock. the resulting cement (commonly quartz or calcite) holds the grains together. cementation is very effective in lithification of sandstones.

Question 15

chemical weathering

Answer 15

the breakdown of rocks at the earths surface by the chemical action of acidic waters, eg the dissolution of limestones and the decomposition of feldspars to clay minerals. contrast physical weathering.

Question 16

cleavage

Answer 16

(in rocks) the property of a rock that enables it to split along parallel, planar surfaces. it is developed by the alignment of mica under pressure during low-grade regional metamorphism.
(in minerals) planes of weakness within a mineral along which it tends to break. the planes are related to the arrangement of atoms in the minerals structure.

Question 17

contact metamorphism

Answer 17

the metamorphism of rocks baked at their contact with a body of magma. affected zones of rock are narrow or localized in extent and occur at relatively shallow depth. contrast regional metamorphism.

Question 18

crystal

Answer 18

a solid with a definite geometric form reflecting the regular arrangements of its constituent atoms.

Question 19

deposition

Answer 19

(earth science): the buildup of sediment which occurs on a surface when sediment can no longer be carried, either in solution or as solid grains that are in suspension or part of the bedload.
(chemistry): the direct conversion of a gas (vapour) into a solid without passage through a liquid phase.

Question 20

dissolved load

Answer 20

material formed by chemical weathering of rocks and carried within a river, stream, lake, sea, etc as dissolved chemicals.

Question 21

dyke

Answer 21

a narrow vertical sheet of igneous rock which has been intruded into older rocks

Question 22

erosion

Answer 22

the wearing away of the earth’s surface by the mechanical removal of rock and mineral fragments due to action of flowing water, ice, or wind, and the abrasive action of moving debris or glaciers.

Question 23

evaporite

Answer 23

a sedimentary rock formed in hot climates by evaporation of salty water to precipitate salts such as the minerals halite (common salt) and gypsum. evaporites may form in enclosed coastal settings.

Question 24

foliation

Answer 24

the layering in metamorphic rocks formed by banding of minerals or the parallel alignment of platy minerals. a characteristic texture of regionally metamorphosed rocks that is caused by pressure during deformation.

Question 25

fossil

Answer 25

any evidence of ancient life, usually preserved in sedimentary rocks

Question 26

fragmental texture

Answer 26

the characteristic appearance of a rock composed of broken fragments of various materials.

Question 27

igneous rocks

Answer 27

a rock formed by the solidification of molten rock material.

Question 28

limestone

Answer 28

a sedimentary, composed largely of calcium carbonate (calcite) that if formed typically by the accumulation on the ocean floor of the shells or skeletal remains of marine organisms.

Question 29

lithification

Answer 29

the collective term for the processes of compaction and chemical change that transform loose sediment into rock.

Question 30

lustre

Answer 30

the surface appearance of a mineral that depends on the way it reflects light. typical terms used to describe a mineral’s lustre include: glassy, resinous, metallic.

Question 31

magma

Answer 31

molten (liquid) rock.

Question 32

metamorphic rocks

Answer 32

a rock that has had its texture and/or mineral composition changed by the action of heat and/or pressure (usually both). a metamorphic rock can be derived from a sedimentary rock, and igneous rock, or a pre-existing metamorphic rock. metamorphic rocks have an interlocking crystalline texture and often display some form of mineral banding or alignment.

Question 33

mica

Answer 33

a sheet silicate material found in many igneous, sedimentary and metamorphic rocks. muscovite is a pale-coloured variety (silvery-grey) that contains little iron or magnesium. biotite is a dark-coloured variety (dark brown to black) that contains applicable iron and/or magnesium.

Question 34

mineral

Answer 34

a solid object, formed by natural processes , whose chemical composition lies within narrow limits such that each consituent atom fits together with its neighbours in a regular three-dimensional pattern. because of this, each typ eof mineral forms a crystal with a characteristic shape

Question 35

ore minerals

Answer 35

minerals which contain useful materials in sufficient abundance that it can be economically viable to mine them

Question 36

partial melting

Answer 36

the incomplete melting of a rock, during which the minerals with the lowest melting temperatures produce a liquid with a composition different from that of the original unmelted rock. an important cause of magmatic diversity

Question 37

physical weathering

Answer 37

the mechanical breakdown of rocks into smaller fragments by physical processes at the earths surface such as frost shattering, penetrating roots, thermal expansion and contraction.

Question 38

pluton

Answer 38

a large (km sized or more) body of igneous rock that was intruded into older rocks

Question 39

regional metamorphism

Answer 39

the metamorphism of vast volumes of rock, accompanied by deformation that occurs mainly during mountain building at subduction zones and zones of continental collision. regionally metamorphosed rocks are characterized by minerals that have grown in alignment as a result of deformation pressure.

Question 40

rock cycle

Answer 40

a conceptual system that links the ways in which rocks are continually being created and destroyed by geological processes operating at and below the earths surface.

Question 41

saltation

Answer 41

a form of bedload transport involving sedimentary grains bouncing along the bottom and ricocheting off other grains

Question 42

schist

Answer 42

a metamorphic rock with an appearance dominated by highly reflective, crudely aligned flakes of platy minerals, such as mica. schist is formed by regional metamorphism.

Question 43

sedimentary bedform

Answer 43

the three-dimensional shape of the surface of sedimentary beds, eg ripples or dunes, which relates to the physical conditions under which the sediment has been transported.

Question 44

sedimentary rock

Answer 44

a rock formed from sediment laid down at the earths surface that has subsequently undergone lifithication by processes such as compaction and cementation. sedimentary rocks usually have a fragmental texture, with individual grains cemented together. some other sedimentary rocks are formed by biological processes (eg coral reefs) or chemical processes (eg evaporites)

Question 45

silicate minerals

Answer 45

minerals that contain silicon and oxygen

Question 46

sill

Answer 46

a narrow horizontal sheet of igneous rock that has been intruded into older rocks

Question 47

slate

Answer 47

A fine-grained metamorphic rock that breaks along smooth, flat, parallel surfaces. Slate is formed by metamorphism at relatively low temperature and pressure of fine-grained, clay-rich sediments. The platy metamorphic minerals in slate (e.g. mica) grow in parallel alignment from clay minerals in response to pressure during deformation.

Question 48

sorting (of sediments)

Answer 48

A measure of the range of grain sizes present in a sediment or a sedimentary rock. If many grains fall within a narrow range of sizes, the sediment is said to be well sorted. If a wide range of grain sizes is present, a sediment is said to be poorly sorted. The degree of sorting can help to indicate the environment in which a sediment was deposited.

Question 49

strata

Answer 49

Layers of sedimentary rock. (The singular, stratum, is synonymous with bed.)

Question 50

suspended load

Answer 50

Sedimentary grains that are transported within flowing water or air, rather than by moving along the sedimentray bed (bedload).

Question 51

texture

Answer 51

(Of a rock) The description of the particles a rock is made from and of the relationship between them. Texture can be fragmental, when individual mineral grains or rock fragments are cemented together (as in a sedimentary rock) or crystalline, where minerals have grown together so that one crystal interlocks with another (as in an igneous rock or a metamorphic rock).

Question 52

transportation

Answer 52

The movement of sedimentary material in flowing water, air or ice.

Question 53

weathering

Answer 53

The degradation of rocks due to physical, chemical or biological action.

Question 54

ammonite

Answer 54

A member of an extinct group of marine molluscs with a chambered, spiral shell. Ammonites were confined to the Mesozoic.

Question 55

background radiation

Answer 55

The naturally occurring level of radioactivity at any location.

Question 56

basalt

Answer 56

A dark-coloured, fine-grained igneous rock, formed as a result of the rapid cooling of mafic magma at the Earth’s surface. Basalt and its intrusive equivalent, gabbro, are the principal components of the oceanic crust. It contains the minerals pyroxene, plagioclase feldspar, and sometimes olivine.

Question 57

best-fit curve

Answer 57

A curve, or line, drawn on a graph of data on a graph so as to give the best representation of the data as a whole. It need not necessarily go through any of the data points and is drawn in such a way that there are approximately the same number of data points above and below the line.

Question 58

bivalve

Answer 58

A member of a class of molluscs that has a shell with two valves. In most bivalves, one valve is the mirror image of the other.

Question 59

brachiopods

Answer 59

Members of the group of marine animals possessing a shell with two valves of dissimilar shape and size. Brachiopods were much more abundant in the Palaeozoic and Mesozoic than today.

Question 60

corals

Answer 60

Members of a group of marine animals which secrete a calcium carbonate skeleton below anemone-like soft tissue.

Question 61

daughter isotope

Answer 61

An isotope produced by the radioactive decay of another isotope (the parent isotope).

Question 62

echinoderms

Answer 62

A type of entirely marine animals with skeletons composed of many interlocking calcite plates. Among echinoderm groups are sea-urchins (echinoids), crinoids and starfish.

Question 63

eons

Answer 63

The largest unit into which the geological timescale is divided. Earth history consists of two Eons: the Precambrian (or Cryptozoic (hidden life)) and the Phanerozoic (visible life).

Question 64

eras

Answer 64

Major division of geological time, based on fossil characteristics in sedimentary rocks. The Phanerozoic Eon is also divided into three Eras: Palaeozoic, Mesozoic and Cenozoic.

Question 65

fault

Answer 65

A plane along which adjacent rocks have moved.

Question 66

fractional cystallisation

Answer 66

The process by which early-formed crystals become separated from the magma in which they crystallised to leave a magma with different composition. An important cause of magmatic diversity. Compare with partial melting.

Question 67

gabbro

Answer 67

A coarse-grained, intrusive igneous rock, with the same chemical composition as basalt, formed by the slow cooling of basaltic magma at depth within the Earth. Gabbro and its extrusive equivalent, basalt, are the principal components of the oceanic crust.

Question 68

gastropods

Answer 68

Members of the group of animals with an unchambered shell which typically coils in an asymmetrical spiral.

Question 69

granite

Answer 69

A coarse-grained intrusive igneous rock composed largely of interlocking crystals of three types of mineral: quartz, feldspar and mica. It often occurs as large plutons.

Question 70

graptolites

Answer 70

Extinct (Palaeozoic) marine colonial organisms with individuals housed in tiny cups arranged along one or more branches. Their fossils can look at first sight like lines drawn in pencil on a rock, hence the name meaning ‘writing on rock’.

Question 71

half-life

Answer 71

The time taken for the number of atoms of a radioactive isotope to be halved by the action of radioactive decay.

Question 72

isotope

Answer 72

An isotope of a given element has the same number of protons, the same number of electrons, but different numbers of neutrons. An isotope is often written as ‘element- mass number’ (for example, lead-235) or, alternatively, the mass number is written as a superscript to the left of the symbol for the chemical element (for example, 235Pb).

Question 73

normal fault

Answer 73

A steeply inclined fault in which the movement has predominantly involved the rocks above the sloping fault plane having moved down, relative to the rocks on the other side of the fault plane. Usually associated with tensional deformation (stretching).

Question 74

nucleus

Answer 74

(Plural: nuclei)

In chemistry and physics, the core of an atom. It contains nearly all of the atomic mass and is positively charged. With the exception of the hydrogen nucleus, which is a single proton, nuclei consist of protons and neutrons.

Question 75

palaentology

Answer 75

The scientific study of fossils.

Question 76

parent isotope

Answer 76

An isotope which undergoes radioactive decay, producing a daughter isotope.

Question 77

periods

Answer 77

Periods Unit of geological time (a subdivision of Era) based largely on the presence of specific fossils in sedimentary rocks. Most geological Periods span several tens of millions of years.

Question 78

principle of fauna succession

Answer 78

The principle that strata contain particular assemblages of fossils in a definite succession, with each stage in this succession representing a particular span of geological time

Question 79

principle of superposition

Answer 79

The principle that, because younger sediments are deposited on older sediments, an individual rock layer is younger than the one beneath it and older than the one above it. Unless the strata have been disturbed or overturned, the oldest layer lies at the bottom.

Question 80

radioactive decay

Answer 80

The spontaneous transformation of one isotope (the parent isotope) into another isotope (the daughter isotope), accompanied by the emission of some energy.

Question 81

radioactivity

Answer 81

The spontaneous transformation of one isotope (the parent isotope) into another isotope (the daughter isotope), accompanied by the emission of some energy.

Question 82

reverse fault

Answer 82

A steeply inclined fault in which the movement has predominantly involved the rocks above the sloping fault plane having moved up, relative to the rocks on the other side of the fault plane. Usually associated with the rocks being compressed sideways.

Question 83

stratigraphic column

Answer 83

The sequence of geological time divisions (Eons, Eras and Periods) arranged in chronological order, with the oldest at the base

Question 84

stratigraphy

Answer 84

The study of strata and their relationships in time and space. Sequences of strata have long been used to establish a generalized geological succession — the stratigraphic column — made up of geological eras and periods, which when given absolute dates forms the geological time-scale.

Question 85

trilobite

Answer 85

A member of an extinct marine group of arthropods confined to the Palaeozoic. Trilobites had an external skeleton, divided lengthways into three lobes, that was shed periodically during growth.

Question 86

unconformity

Answer 86

The absence of strata from a particular time interval in a certain region, due either to non-deposition, or to erosion of any sediment that had been deposited. The term also refers to the actual contact between unconformable rocks. An unconformity is often recognized by a difference in the angle of layering in adjacent sets of strata.

Question 87

uniformitarianism

Answer 87

The concept, fundamental to geology, that geological processes which operate today also operated in the past. It is the basis of the frequently quoted maxim ‘the present is the key to the past’.

Question 88

absolute plate motion

Answer 88

The movement of a tectonic plate relative to a fixed reference point such as a mantle plumes.

Question 89

abyssal plain

Answer 89

The part of the ocean floor that lies between 4 km and 6 km below the surface. Abyssal plains are generally flat and they make up the major part of the ocean floor.

Question 90

active continental margin

Answer 90

A type of convergent plate margin where oceanic lithosphere is subducted beneath a continental margin, such as exists along the west coast of South America. (See also ocean/continent subduction zone.)

Question 91

asthenosphere

Answer 91

A weaker, more easily deformed region of the mantle that is below the lithosphere.

Question 92

bathymetry

Answer 92

The measurement of depth of water in seas, essentially the topography of the seabed.

Question 93

biomodal distribution

Answer 93

A distribution of data that exhibits two distinct peaks (i.e. has two modes).

Question 94

body waves

Answer 94

A seismic wave that travels through the interior of the Earth. There are two types of body wave: a P wave and an S wave.

Question 95

conservative plate boundary

Answer 95

A type of plate boundary where the plates move laterally past each other without convergence or divergence.

Question 96

continental drift

Answer 96

The movement of continents over the surface of the Earth through geological time.

Question 97

convergent plate boundary

Answer 97

A type of tectonic plate boundary where the plates move towards each other, also known as a subduction zone.

Question 98

core

Answer 98

The central part of the Earth, composed mainly of iron. The outer core is liquid, the inner core is solid.

Question 99

cross section

Answer 99

A representation of a vertical slice through the Earth to show an aspect of the subsurface.

Question 100

crust

Answer 100

The upper seismic layer of the Earth. The crust has a relatively low density and low seismic wave speeds. It is about 7 km thick under oceans (oceanic crust), and 20–80 km thick (averaging 35 km) under continents (continental crust).

Question 101

divergent plate boundary

Answer 101

A type of tectonic plate boundary where the plates move apart from one another, also known as a mid-ocean ridge (or spreading centre).

Question 102

earthquake magnitude

Answer 102

A quantitative measure of the size of an earthquake, obtained from the amount of energy released.

Question 103

epicentre

Answer 103

The point on the Earth’s surface directly above the focus of an earthquake.

Question 104

focal depth

Answer 104

The depth of the focus of an earthquake below the Earth’s surface.

Question 105

focus

Answer 105

The location (point of origin) of an earthquake. This is usually well below the Earth’s surface. (Plural = foci)

Question 106

fracture zone

Answer 106

A liner deep sea fault that transects and displaces a mid ocean ridge.

Question 107

full spreading rate

Answer 107

In plate tectonics, the rate at which two points lying either side of an oceanic ridge crest diverge.

Question 108

GPS

Answer 108

Global Positioning System. A system of fixing the location of a point on the Earth’s surface with reference to a configuration of satellites.

Question 109

graben

Answer 109

A fault edged, downthrown block of crust that forms a linear valley.

Question 110

half spreading rate

Answer 110

In plate tectonics, the rate at which a single point on one side of a ridge moves away from the oceanic ridge crest.

Question 111

hotspot

Answer 111

A volcanic area above a shallow region of anomalously hot mantle.

Question 112

hotspot track

Answer 112

A chain of active and extinct volcanoes that have formed on a moving plate above a stationary hotspot.

Question 113

hydrothermal circulation

Answer 113

The circulation of hot fluids in the vicinity of a magma body for example at a mid-ocean ridge.

Question 114

hypsometric plot

Answer 114

A histogram showing the relative proportions of the Earth’s surface area at different altitudes and depths.

Question 115

inclined seismic belt

Answer 115

An inclined zone of earthquakes (also known as a Wadati Benioff zone) extending several hundred kilometres into the Earth at a subduction zone. A Wadati–Benioff zone defines the position of a cold subducted slab of lithosphere.

Question 116

island arc

Answer 116

The chain of volcanic islands on the overriding plate at a subduction zone where two plates of oceanic lithosphere converge. An island arc lies parallel to an ocean trench. (See also ocean/ocean subduction zone.)

Question 117

lava

Answer 117

Molten igneous rock (magma) that flows over the Earth’s surface. The term lava flow can also be used to describe the body of rock formed after the molten lava has cooled and solidified.

Question 118

lithospheric plate

Answer 118

An area of lithosphere, the edges of which are defined by a seismic zone. This is usually abbreviated to plate. Also known as a tectonic plate.

Question 119

mantle

Answer 119

The layer of the Earth between the crust and the core .

Question 120

mantle plume

Answer 120

A localised area of anomalously hot mantle that rises due to buoyancy. Mantle plumes may give rise to hotspots when they melt at shallower levels.

Question 121

mid-ocean ridge

Answer 121

A broad ridge a few thousand kilometres across and 2– 3 km high on the ocean floor, extending for many thousands of kilometres. Mid-ocean ridges do not always lie in the centres of oceans. A mid-ocean ridge is a divergent plate boundary.

Question 122

ocean/continent subduction zone

Answer 122

A type of convergent plate margin where oceanic lithosphere is subducted beneath a continental margin, such as exists along the west coast of South America. (See also ocean/continent subduction zone.)

Question 123

ocean/ocean subduction zone

Answer 123

The chain of volcanic islands on the overriding plate at a subduction zone where two plates of oceanic lithosphere converge. An island arc lies parallel to an ocean trench. (See also island arc.)

Question 124

orogeny

Answer 124

The processes and/or sum of events during which a mountain belt is formed, e.g. the Caledonian Orogeny. An orogeny usually involves the convergence of lithospheric plates, causing folding, faulting, metamorphism and igneous activity. Also referred to as continental collision.

Question 125

plate boundary

Answer 125

The edge of a tectonic plate, where it interacts with a neighbouring plate.

Question 126

plate tectonics

Answer 126

The theory that the Earth’s surface is composed of a number of lithospheric plates that can move around. It combines evidence for continental drift with the mechanism of sea-floor spreading, so providing an explanation that links previously unrelated features of the Earth, such as the distribution and shape of mountain belts, the location of seismic zones, volcanism and the shape of the ocean floor.

Question 127

polarity of subduction

Answer 127

The direction of subduction at a convergent plate boundary.

Question 128

pyroclastic flow

Answer 128

A flow of materials from a pyroclastic eruption down the side of a volcano.

Question 129

seismic waves

Answer 129

A wave in the Earth, generated by an earthquake (or an explosion).

Question 130

seismogram

Answer 130

A paper record of ground motion due to a seismic wave recorded by a seismometer. Sometimes referred to as a seismic trace or seismograph.

Question 131

seismology

Answer 131

The study of earthquakes.

Question 132

seismometer

Answer 132

An instrument that measures and records motion of the ground surface.

Question 133

slip

Answer 133

The relative displacement to the two sides of a fault plane which were originally coincident.

Question 134

SONAR

Answer 134

An acoustic survey system which uses the reflection of high frequency sount waves from a surface to image its surface. Frequently deployed from ships to map out the surface of the seabed. (An acronym derived from sound navigation and ranging.

Question 135

subduction

Answer 135

The process by which an oceanic lithospheric plate sinks beneath another plate of either oceanic or continental character.

Question 136

subduction zone

Answer 136

A region of the Earth where oceanic lithosphere subducts (sinks) beneath the edge of another lithospheric plate at a convergent plate boundary.

Question 137

surface waves

Answer 137

A seismic wave that travels at and near the surface of the Earth.

Question 138

s wave (shear wave)

Answer 138

A type of seismic wave; the slower type of body wave. This is a transverse wave in which the rock moves at a right angle to the direction of wave motion.

Question 139

tectonic plates

Answer 139

An area of lithosphere, the edges of which are defined by a seismic zone. This is usually abbreviated to plate. Alo known as a lithospheric plate.

Question 140

topography

Answer 140

Used in this context to describe the range and distribution of elevation of the surface of the Earth.

Question 141

trench (submarine)

Answer 141

An elongate depression on the ocean floor that runs parallel to an active continental margin or to an adjacent chain of volcanic islands (island arc). Oceanic trenches are up to 11km deep, typically 50-100km wide and may be thousands of kilometres long.

Question 142

triangulation

Answer 142

Locating a point with reference to three survey points at a known distance of separation.

Question 143

tsunami

Answer 143

Ocean waves caused by movement of the ocean floor by an earthquake under the ocean. Tsunami can travel great distances across an ocean. They have a small wave height in the deep ocean, but increase in height significantly when they reach a coast, and can be very destructive.

Question 144

vector

Answer 144

An arrow that contains information about direction and magnitude. Vectors of tectonic plate motion show both direction and speed which is normally indicated by length.

Question 145

volcanic ash

Answer 145

Fine (<2mm) solid particulate material erupted from a volcano.

Question 146

volcano

Answer 146

A naturally occurring vent or fissure at the Earth’s surface through which molten, solid and gaseous materials erupt.

Question 147

watadi beniof zone

Answer 147

An inclined zone of earthquakes extending several hundred kilometres into the Earth at a subduction zone. A Wadati–Benioff zone defines the position of a cold subducted slab of lithosphere.

Question 148

anthropocene

Answer 148

A proposed epoch relating to significant human impact on the geology and ecosystems on Earth

Question 149

aquifier

Answer 149

Undeground, water-saturated permeable rock or unconsolidated materials

Question 150

assimilation

Answer 150

The conversion of nutriment into a useable form that is incorporated into the tissues and organs or an organism. Examples of assimilation include photosynthesis in plants in which CO2 and water are converted into carbohydrates, or nitrogen fixation by bacteria in which gaseous N2 is converted into ammonia. Animals assimilate food by eating plants or each other.

Question 151

atmosphere

Answer 151

A layer of gases surrounding a planet or other body held in place by the gravity of that body

Question 152

atom

Answer 152

An atom is the smallest constituent unit of matter that has the properties of a chemical element; each chemical element is characterised by a different type of atom. Atoms are roughly 10–10 m across.

Question 153

biogeochemical cycle

Answer 153

A pathway (or pathways) by which a chemical substances moves through both the living (biosphere) and non-living (lithosphere, atmosphere, and hydrosphere) components of Earth. They occur because chemical elements on Earth are recycled, unlike energy.

Question 154

biomass

Answer 154

The amount of living material, usually in some area or volume. If quantified, marine biomass is often expressed in grams of carbon per unit area of sea-surface (or unit area of sea-bed, in the case of benthic ecosystems), i.e. gC m–2. Biomass is also used to refer to the matter of which an individual organism is composed.

Question 155

biosphere

Answer 155

The part of the Earth inhabited by life.

Question 156

carbonate counter pump

Answer 156

A sub-cycle of the carbon cycle, whereby carbon dioxide (CO2) reacts with water to form carbonic acid and bicarbonate. The carbonate pump allows the ocean to take up much more CO2 than if CO2 just dissolved in water

Question 157

carbon cycle

Answer 157

The global transfer of carbon between various carbon reservoirs in the environment, involving both living organisms (biological cycle) and the non-living environment, such as soil, water, rocks and air (geochemical cycle).

Question 158

carbon footprint

Answer 158

The amount of carbon dioxide (or carbon dioxide equivalent for other greenhouse gases) released into the atmosphere as a result a particular acivity.

Question 159

closed system

Answer 159

A physical system in which no matter is exchanged with its surroundings.

Question 160

condensation

Answer 160

The process whereby a substance changes from a gas to a liquid, e.g. water changes from water vapour to liquid water.

Question 161

decomposition

Answer 161

The gradual disintegration of dead organic matter. Some decomposition occurs through physical factors such as wind and water, but it is mostly achieved by bacteria. See detritivore.

Question 162

denitrification

Answer 162

A process, facilitated by microbes, in which nitrate is reduced through a series of intermediate products to ultimately form nitrogen gas (N2)

Question 163

discharge

Answer 163

The flowing of a liquid (or gas) from where it has been confined.

Question 164

eutrophication

Answer 164

The enrichment of an environment, often a water body, with nutrients. It can refer to the enrichment of an environment with excessive amounts of nutrients.

Question 165

evaporation

Answer 165

The process whereby a substance changes from a liquid to a gas, e.g. liquid water evaporates to form water vapour.

Question 166

evotranspiration

Answer 166

The sum of both the evaporation from the soil and other surfaces and transpiration from plants, which describes the process by which water is transferred from land and water surface to the atmosphere.

Question 167

fixation

Answer 167

The process in which a substance is changed from the gaseous or solution phase, into a useable stable form, as in carbon dioxide fixation or nitrogen fixation.

Question 168

flow

Answer 168

The movement of a substance in a continuous stream or current.

Question 169

flux

Answer 169

A process of flowing or change.

Question 170

gas exchange

Answer 170

The biological process by which gases move passively by diffusion across a surface. Gas exchange occurs between the air and cells inside a leaf in plants, and between air and blood in the lungs as examples.

Question 171

hydrosphere

Answer 171

The part of the Earth that includes water, either in or on the surface of the Earth (including the oceans, rivers, lakes, ice), together with water in the atmosphere.

Question 172

lithosphere

Answer 172

The rigid outer layer of the Earth, which includes the crust. It is made up of plates that may be oceanic, continental or both.

Question 173

nitrate

Answer 173

The anion NO3− found in compounds such as sodium nitrate NaNO3 or potassium nitrate (saltpetre) KNO3.

Question 174

nitrification

Answer 174

The aerobic process in which ammonia is oxidised to nitrite and nitrate by the nitrifying bacteria.

Question 175

nitrite

Answer 175

The anion NO2-, found in compounds such as sodium nitrite NaNO2 or potassium nitrite KNO2

Question 176

nitrogen fixation

Answer 176

The conversion of nitrogen gas (N2) into ammonia (NH3) or other nitrogen-containing molecules that can be used by living organisms (the reverse process to dintrification).

Question 177

organic carbon

Answer 177

Carbon in compounds found in living things or the remains of living things. For example, plants produce simple organic carbon compounds through photosynthesis.

Question 178

organic carbon pump

Answer 178

The biologically-driven transformation of carbon dioxide into organic carbon materials, their deposition into deep sea waters and sediments in the ocean, and their decomposition at depth

Question 179

percolation

Answer 179

The process of a liquid slowly passing through a filter or porous material.

Question 180

phases (chemical)

Answer 180

Physically distinctive forms of matter, such as a solid, liquid or gas.

Question 181

photosynthesis

Answer 181

The process whereby plants utilise carbon dioxide, water and light energy from the Sun to manufacture organic compounds (carbohydrates).

Question 182

pool

Answer 182

In a global cycle (e.g. water or carbon), pools provide a means of classifying cycled material by the type of location, irrespective of its real geographical location. For example, pools in the carbon cycle include the plants and fossil fuel deposits.

Question 183

precipitation

Answer 183

A collective term referring to all the forms in which water can fall from the atmosphere onto the Earth’s surface (as rain, snow, sleet or hail).

Question 184

pump

Answer 184

In biogeochemical cycles, a pump describes a process which drives fluxes and the name often indicates the main driver of the pump (i.e. a biological pump includes reactions driven by lifeforms).

Question 185

reservoir

Answer 185

In a global cycle (e.g. water or carbon), reservoirs provide a means of classifying cycled material by the type of location, irrespective of its real geographical location. For example, reservoirs in the water cycle include the atmosphere, the oceans, ice and snow.

Question 186

residence time

Answer 186

The average length of time that a molecule remains in a particular reservoir.

Question 187

run-off

Answer 187

Something that drains or flows off, such as rain that flows off land into streams.

Question 188

solution pump

Answer 188

Also known as the solubility pump this is the absorption or release of CO2 by water, following changes in solubility of gaseous CO2

Question 189

store

Answer 189

In a global cycle (e.g. water or carbon), stores provide a means of classifying cycled material by the type of location, irrespective of its real geographical location. For example, reservoirs in the water cycle include the atmosphere, the oceans, ice and snow.

Question 190

system

Answer 190

This is the part of the world in which there is a particular interest. In biology it is often a set of components working together as parts of an interconnecting network. In the context of a chemical reaction, it could simply be the contents of a reaction mixture.

Question 191

terrestrial

Answer 191

Related to land or the planet Earth, but also refers to organisms that live on land or processes that occur on land instead of in water.

Question 192

water cycle

Answer 192

The continuous circulation of water on Earth between ocean, atmosphere, land, biological organisms, etc. It involves water changing its state between solid (ice), liquid (water), and gas (water vapour).

Question 193

autotroph

Answer 193

An organism that makes its own carbon-based material starting with carbon dioxide. An autotroph is also known as a primary producer. Almost all plants are autotrophs; they convert carbon dioxide into carbon based material by photosynthesis.

Question 194

carnivores

Answer 194

An organism that obtains its carbon-based materials by consuming living or recently killed animals, either in whole or in part, i.e. a type of heterotroph.

Question 195

carrion

Answer 195

The decaying flesh of dead animals.

Question 196

commensalism

Answer 196

An association between two species in which one benefits and the other derives neither benefit nor harm.

Question 197

community

Answer 197

Considered as a whole, the various populations of organisms (micro-organisms, plants and animals) that inhabit a particular area, and interact together.

Question 198

competition

Answer 198

An interaction between organisms or species in which both the organisms or species are harmed. Limited supply of at least one resource (such as food, water, and territory) used by both can be a factor.

Question 199

consumers

Answer 199

An organism that cannot manufacture its own carbon-based materials starting from carbon dioxide and therefore feeds on other organisms. Also known as a heterotroph. Compare with producer.

Question 200

dcomposers

Answer 200

An organism which breaks down dead organisms through decomposition, including fungi and bacteria.

Question 201

detritivores

Answer 201

Animals that feed primarily on detritus, i.e. organic debris from plants and animals.

Question 202

ecosystem

Answer 202

All the (interdependent) communities of organisms in a particular geographical area, plus the physical environment that they inhabit.

Question 203

ecosystem balance

Answer 203

A state of dynamic equilibrium within an ecosystem in which genetic, species and ecosystem diversity remain relatively stable, subject to gradual changes through natural succession.

Question 204

food chain

Answer 204

A linear sequence of organisms in which each organism (or group of organisms) is food for the next member in the sequence.

Question 205

food web

Answer 205

A schematic representation of the feeding interactions within an ecosystem or community. Food webs contain multiple food chains and one organism can have more than one food source, thereby linking food chains together.

Question 206

guild

Answer 206

A guild is any group of species that exploit the same resources, or who exploit different resources in related ways.

Question 207

habitat

Answer 207

The physical and biological environment in which an organism lives.

Question 208

herbivores

Answer 208

An organism that obtains its carbon-based materials by consuming living plant (or fungal) material, i.e. a type of heterotroph.

Question 209

herbivory

Answer 209

The act of eating plants and a herbivore is an animal that eats plants

Question 210

heterotroph

Answer 210

An organism that cannot manufacture its own carbon-based materials starting from carbon dioxide and therefore feeds on other organisms. A heterotroph is also known as a consumer. Compare with autotroph.

Question 211

individual

Answer 211

A single, separate organism distinguished from others of the same kind.

Question 212

mutualism

Answer 212

An association between two species in which both partners confer some benefit.

Question 213

omnivores

Answer 213

Organisms which obtain their food from both other animals and plants.

Question 214

parasitism

Answer 214

A non-mutual association between species, where one species, the parasite, benefits at the expense of the other, the host, often without killing the host. The parasite is often much smaller than its host.

Question 215

population

Answer 215

A group of organisms belonging to the same species which live in a defined place.

Question 216

predation

Answer 216

One animal feeding upon another.

Question 217

primary consumer

Answer 217

An organism that obtains its carbon-based materials by consuming another organism either whole or in part, either living or dead, and is the first heterotrophic species in a food chain. These organisms consume plant material.

Question 218

primary producer

Answer 218

An organism that makes its own carbon-based material, starting from carbon dioxide. A producer is also known as an autotroph. Almost all plants are producers; they convert carbon dioxide into carbon based material by photosynthesis.

Question 219

secondary consumers

Answer 219

An organism that obtains its carbon-based materials by consuming another organism either whole or in part, either living or dead, and is the second heterotrophic species in a food chain.

Question 220

species

Answer 220

A group of organisms that are similar to one another in appearance and/or behaviour, and that differ in some way from other closely-related groups of organisms. There is usually a significant degree of reproductive isolation between species that reproduce sexually. The species is the level of taxonomic classification immediately below genus. The second part of an organism’s scientific label identifies it as belonging to a particular species within its genus. For example, the domestic cat is uniquely identified by the scientific label Felis catus (which can be abbreviated to F. catus, providing there is no ambiguity) in contrast to other species within the genus Felis, such as the wild cat (F. silvestris).

Question 221

thermogenic

Answer 221

Able to produce heat.

Question 222

trophic cascade

Answer 222

An ecological phenomenon triggered by the addition or removal of a large part of a trophic level, in which reciprocal changes in the relative populations of other tropic levels occur through a food chain, which often results in dramatic changes in ecosystem structure and nutrient cycling.

Question 223

trophic level

Answer 223

The term used to describe ‘feeding’ levels in food chains or in pyramids of numbers, biomass or energy. Each link in a food chain constitutes a trophic level.

Question 224

annual plants

Answer 224

Plants with a life cycle that only lasts one year – they grow from seed, bloom, produce seeds and die in one year.

Question 225

anthropogenic

Answer 225

Caused by humans

Question 226

biome

Answer 226

the community of species which will naturally develop (usually via succession) in an area

Question 227

carrying capacity

Answer 227

The theoretical maximum size of a population which an ecosystem can support. This is usually controlled by the resource availability.

Question 228

climax community

Answer 228

The stable community of plants and animals which ultimately result from succession in a given environment.

Question 229

colonization

Answer 229

The establishment of a new group of species in an area which have moved in from another area

Question 230

cyclicity

Answer 230

Oscillating (usually about a fixed mean) at a periodic interval.

Question 231

ecosystem services

Answer 231

Benefits and resources provided by the ecosystem

Question 232

empirically deprived

Answer 232

Determined by experimentation or observation, rather than purely from theory

Question 233

endemic

Answer 233

Native to a certain place.

Question 234

environment

Answer 234

The living (plants and animals) and non-living (resources) of an area or location including external conditions (physical climate) which affect life.

Question 235

eutrophic

Answer 235

Rich in nutrients (usually used to describe water bodies)

Question 236

hypoxic waters

Answer 236

Low oxygen water in which no life survives. Defined as where oxygen is:
<2(mg/L)

Question 237

invasive species

Answer 237

A species of plant or animal which has colonised an area it is not endemic to, usually outside of the normal sequence of succession and often introduced by humans.

Question 238

logistic growth model

Answer 238

A growth model for a population in which rate of growth decreases as the population approaches a carrying capacity

Question 239

mathematical models

Answer 239

A way of describing a real world system using mathematical structures

Question 240

nutrients

Answer 240

Chemical elements and compounds which are the fundamental building blocks of living organisms

Question 241

oligotrophic

Answer 241

having few or little nutrients (usually used to describe water bodies).

Question 242

perennial plants

Answer 242

Any plant that lives for more than two years

Question 243

pioneer species

Answer 243

The first species to colonise a bare (lifeless) environment

Question 244

planktic organisms

Answer 244

those (often microscopic) organisms that live free floating in the water column and cannot propel themselves against a current.

Question 245

primary succession

Answer 245

The process of colonisation of an area from a standing start of bare-Earth. Primary succession will involve a number of different species in sequence, from early pioneer species which need little or no soil to more complex plants which require more ecosystem services, usually in a predictable order.

Question 246

proxy

Answer 246

A measurement or indicator which can be used as an indirect estimate of another variable which it is correlated with.

Question 247

rarefaction curve

Answer 247

A plot of species number vs. number of individuals sampled, used to estimate species richness and to help choose appropriate sampling strategy.

Question 248

red tides

Answer 248

Marine waters turned red by vast blooms of planktic algae (dinoflagellates cause the red colouration). Often caused by eutrophication.

Question 249

representative

Answer 249

A representative sample is one which has properties which accurately reflect the properties of the population from which it is taken.

Question 250

sample

Answer 250

A subset selected from a defined population.

Question 251

secondary succession

Answer 251

The process of colonisation of an area which has been previously populated by plants and animals that have been removed by a disturbance. Secondary succession will involve a number of different species, usually in a predicable order.

Question 252

species richness

Answer 252

The number of different species in a population, this population can be a landscape, ecosystem or region.

Question 253

succession

Answer 253

The process of progressive replacement of early pioneer species with successive species until a stable climax community is reached.

Question 254

absorbance

Answer 254

A measure of the amount of light (of a specified wavelength) absorbed by a substance

Question 255

acid rain

Answer 255

Precipitation containing high levels of acidic components typically as a result of atmospheric pollution

Question 256

activation energy

Answer 256

The threshold level of energy that a reactant must possess for a specific chemical reaction to occur

Question 257

ALARA

Answer 257

(As Low As Reasonably Achievable) - a key principle in the balancing of risk and benefit when evaluating procedural safety.

Question 258

ALARP

Answer 258

(As Low as Reasonably Practicable) - a key principle in the balancing of risk and benefit when evaluating procedural safety.

Question 259

alpha particle

Answer 259

(α-particle) The particle that is ejected in alpha-decay. An α-particle is a helium nucleus, which is represented as 4/2 HE (or He2+, because it is a helium atom stripped of both of its electrons)

Question 260

anemometer

Answer 260

A device used to measure wind speed

Question 261

antibiotic

Answer 261

A class of chemical compound that can kill or inhibit the growth of bacteria

Question 262

antibiotic resistance

Answer 262

The capacity of bacteria to resist the effects of exposure to antibiotics

Question 263

antinbiotics

Answer 263

Plural of antibiotic.

Question 264

aseptic

Answer 264

Conditions in which contamination by (typically pathogenic) microorganisms is prevented

Question 265

autoclave

Answer 265

A device used to subject solids and liquids to sustained high temperature and pressure for sterilisation

Question 266

bacilli

Answer 266

Rod shaped bacteria

Question 267

bacteria

Answer 267

A domain consisting of prokaryote organisms; there are two such domains, the other being Archaea

Question 268

beaufort scale

Answer 268

Beaufort scale of wind force - scale relates wind speed to specific conditions at sea and/or on land

Question 269

beta particle

Answer 269

A fast-moving electron emitted during a particular type of radioactive decay known as β -decay. Being electrons, β-particles carry a negative charge. β-particles are, in fact, only emitted in beta-minus decay. In beta-plus decay a positively charged particle (a positron or antielectron) is emitted instead

Question 270

binary fission

Answer 270

A form of asexual reproduction common in prokaryotes in which a single mature cell divides in half to produce two new identical cells

Question 271

biore mediation

Answer 271

The use of microorganisms to degrade contaminants/pollutants in a given environment/location

Question 272

celcius scale

Answer 272

A scale used for measuring temperature. The normal freezing temperature of water on this scale is defined as 0 °C (zero degrees Celsius) and the normal boiling temperature of water as 100 °C (one hundred degrees Celsius).

Question 273

cloud chamber

Answer 273

A particle detecting instrument in which ionising radiation can be visualised

Question 274

cocci

Answer 274

Spherical shaped bacteria

Question 275

collision theory

Answer 275

Theory that conceptualises chemical reactions as a series of collisions between reactant particles. Used to make qualitative deductions about reactions and reaction rates

Question 276

compound leaf

Answer 276

A leaf consisting of a common stalk supporting multiple leaflets

Question 277

concentration

Answer 277

A measure of the amount of solute (often a solid) dissolved in a specific volume of solution. Units relate to the mass (g or kg) or number of moles of solute in a volume of solution, e.g. g litre−1 or mol litre−1.

Question 278

constant of proportionality

Answer 278

(or proportionality constant) In a directly proportional relationship, the constant factor that expresses how the dependent variable depends upon the independent variable.
If two quantities are proportional to each other, for example y ∝ x, then we can write y = kx, where k is the constant of proportionality.

Multiplying the independent variable by the proportionality constant generates the value of the dependent variable.

Question 279

control measure(s)

Answer 279

Action(s) that can be performed to reduce the potential of hazard exposure

Question 280

cosmic rays

Answer 280

Source of radiation (high energy particles) originating from beyond Earth’s atmosphere

Question 281

cumulative

Answer 281

An increase in parameter magnitude due to the successive additive effect of multiple contibuting events

Question 282

cuvette

Answer 282

A small tube with a square cross-section open at one end to hold samples for analysis in a spectrophotometer

Question 283

deciduous

Answer 283

Denotes a plant/tree/shrub that sheds leaves seasonally

Question 284

decline phase

Answer 284

Phase of bacterial growth in which the number of dead/dying cells in a population exceeds the number of new cells being added to the population

Question 285

deforestation

Answer 285

Removal of forest (typically rainforest) and conversion of land for non-forest use (typically yielding a less biodiverse ecosystem)

Question 286

dependant variable

Answer 286

A measured quantity, the value of which depends on the value chosen for another quantity (the independent variable). On a graph, the dependent variable is plotted on the y axis. For example, if an investigator selected children of certain ages and measured their heights, then height would be the dependent variable.

Question 287

diptheria

Answer 287

Highly contagious bacterial infection that affects the upper airway

Question 288

DNA

Answer 288

Abbreviation for deoxyribonucleic acid. The class of molecules that carries the genetic information of organisms and is thus the genetic material. DNA is a polymer whose monomers are nucleotides, which consist of three component parts joined by covalent bonds: a phosphate group, a sugar (deoxyribose) and a base. There are four different bases in DNA: adenine (A), guanine (G), cytosine (C) and thymine (T). Nucleotides joined together form polynucleotides. Each DNA molecule consists of two polynucleotide chains intertwined to form a characteristic double helix. DNA molecules are by far the largest known molecules in living organisms; some have relative molecular masses of many billions! DNA carries the genetic information of the cell, coded as a sequence of nucleotides (and hence a sequence of bases).

Question 289

DNA mutation

Answer 289

A change in the nucleotide sequence of a piece of DNA

Question 290

electromagnetic wave

Answer 290

Manifestation of the transfer of energy associated with electromagnetic radiation. Produced by the interaction of perpendicular electric and magnetic fields.

Question 291

evergreen

Answer 291

Denotes a plant/tree/shrub that retains green leaves throughout the year

Question 292

exponential

Answer 292

An exponential change is one in which the value of a quantity decreases or increases by the same factor in equal intervals. Thus the shape of the graph obtained by plotting the number of radioactive decays from a sample against time is described as an exponential decay, or a falling exponential since the graph falls by a constant factor of two for every half-life that elapses

Question 293

farenheit (scale)

Answer 293

A scale used for measuring temperature. The normal freezing temperature of water on this scale is defined as 32 °F (32 degrees Fahrenheit) and the normal boiling temperature of water as 212 °F (two hundred and twelve degrees Fahrenheit).

Question 294

false negative

Answer 294

Case in which a specified condition/outcome/attribute is declared to be absent when it isn’t

Question 295

false positive

Answer 295

Case in which a specified condition/outcome/attribute is declared to be present when it isn’t

Question 296

falsifiable

Answer 296

An inherent characteristic of all scientific theories and hypotheses that allows for them to be proven false

Question 297

first order reaction

Answer 297

A chemical reaction the rate of which is proportional to the concentration of a given reactant

Question 298

foliage

Answer 298

Collection of leaves supported by a plant/tree/shrub

Question 299

frequency (wave)

Answer 299

The number of complete cycles of a wave that pass a certain fixed point in a unit of time. Conventionally measured in the SI unit of hertz, Hz (or equivalently s–1). It is equal to one over the period of a wave, f = 1/T , and related to the wavelength λ and speed v of a wave by v = fλ.

Question 300

gamma ray

Answer 300

A type of electromagnetic radiation of short wavelength which is commonly emitted during radioactive decay. It is not deflected by a magnetic field, and this distinguishes it from alpha-particles and beta-particles.

Question 301

generation time

Answer 301

The time required for the number of bacteria in a population to double

Question 302

growth medium

Answer 302

A mixture of substances in liquid, solid, or semi-solid form that can be used to support the growth of microorganisms like bacteria

Question 303

hazard

Answer 303

An object/event/process that could potentially cause harm

Question 304

histogram

Answer 304

A graphical representation in which the horizontal axis is divided into a set of intervals (usually equal). On each of these intervals a rectangle is constructed with a width equal to the interval, and a height that represents the value of the quantity on the vertical axis that applies at the particular interval. For example, the intervals could be the months in the year, and the vertical axis could be the mean monthly rainfall. Note that there is no gap between the rectangles.

Question 305

hypothesis

Answer 305

A tentative explanation, based on the available evidence, which accounts for observations or facts. It may be tested by making further observations, and may be modified in the light of new evidence or observations.

Question 306

independent variable

Answer 306

A quantity, the value of which is chosen by the investigator. On a graph, the independent variable is plotted on the x axis. For example, if an investigator selected children of certain ages and measured their heights, then age would be the independent variable, and height the dependent variable

Question 307

ionisation

Answer 307

As in ionising

Question 308

ionising

Answer 308

Capacity (of radiation) to cause the removal of electron(s) from a molecule/atom to result in the formation of ion(s)

Question 309

ionising radiation

Answer 309

A type of radiation which has the capacity to remove one or more electrons from a molecule/atom and results in the formation of an ion/ions.

Question 310

lag phase

Answer 310

Phase of bacterial growth in which the population of cells adapts to the environment. This may require the cells to make metabolic changes before optimal growth rates can be achieved

Question 311

leaf area index

Answer 311

Ecological parameter representing leaf area per unit ground area. (Also sometimes abbreviated to ‘LAI’.)

Question 312

linear

Answer 312

Property of a mathematical relationship between two variables/factors that can be represented as a straight line on a graph

Question 313

logarithmic increase

Answer 313

Mathematical function that represents the optimum growth of a bacterial population dependent on binary fission

Question 314

log phase

Answer 314

Phase of bacterial growth in which the population is able to grow at an optimum rate (logarithmically)

Question 315

Luria-Bertani (LB) broth

Answer 315

A commonly used formulation of growth medium for bacteria

Question 316

meteorologist/meteorology

Answer 316

A scientist who observes, analyses and makes predictions about the weather/The branch of science focused on the study of the atmosphere and events within it

Question 317

microbiological/microbiology

Answer 317

Pertaining to the branch of science specialised in the study of microorganisms (bacteria, viruses, protozoa, funghi and archae)

Question 318

modal size class

Answer 318

The most abundant grain size class in a sediment sample

Question 319

mode

Answer 319

The most frequent value present in a series of values

Question 320

MODIS

Answer 320

Moderate Resolution Imaging Spectroradiometer - a type of instrument carried by the NASA satellites Terra and Aqua that collects data about the Earth’s surface

Question 321

monsoon

Answer 321

A climate characterised by significant seasonal changes in prevailing wind direction that typically result in large changes in rainfall and distinct ‘wet’ and ‘dry’ seasons

Question 322

naturally occuring radioactive material

Answer 322

Radioactive substances that are widely distributed in the Earth’s crust

Question 323

non-ionising

Answer 323

Any radiation that carries insufficient energy to result in the ionisation of any atoms or molecules it is exposed to

Question 324

null hypothesis

Answer 324

Formalised statement predicting that there will be no difference between the various groups or conditions being compared in an experiment

Question 325

nutrient cycle

Answer 325

The sequence of events and processes that describes how nutrients are removed from the physical environment, transferred to biological systems (organisms) and then returned to the physical environment (recycled)

Question 326

parameter

Answer 326

A characteristic that defines a particular system or specifies the range/limits of the operation of a system

Question 327

pathogen

Answer 327

A disease-causing organism, including bacteria and viruses, and also parasites, such as tapeworms

Question 328

pathogens

Answer 328

The plural of pathogen.

Question 329

peer review

Answer 329

The process by which work (typically scientific/technical/academic) of an individual or group of individuals is evaluated by others working in the same or a very similar field

Question 330

penicillium notatum

Answer 330

Species of fungus (also known as Penicillium chrysogenum) that produces the antibiotic penicillin

Question 331

permeability

Answer 331

A measure of the ease with which fluid can transit through rock

Question 332

perpendicularly

Answer 332

At right angles (ninety degrees) to

Question 333

petri dish

Answer 333

A shallow glass or plastic dish with a circular cross section and removable lid that is often used to contain growing microorganisms or eukaryotic cells

Question 334

porosity

Answer 334

A measure of the amount of open space contained within rock

Question 335

post antibiotic era

Answer 335

Era of medicine with no viable antibiotic available.

Question 336

PPE

Answer 336

Personal Protective Equipment - any of a range of items that are designed to protect individuals from health and safety hazards

Question 337

product

Answer 337

(Of a chemical reaction) The new material (or materials) formed as a result of a chemical reaction.

Question 338

prokaryotes

Answer 338

An organism comprising a single cell (with a few exceptions) in which the DNA is not contained within a nucleus. Prokaryotes are members of either the domain Archaea or the domain Bacteria.

Question 339

proportional (to)

Answer 339

Two quantities are said to be proportional to each other if, when the value of one is multiplied (or divided) by a certain amount, the value of the other also becomes multiplied (or divided) by the same amount. For example, the cost of petrol is proportional to the volume of petrol bought, so the cost of buying 50 litres of petrol is twice the cost of buying 25 litres of petrol which is five times the cost of buying 5 litres. This is equivalent to the two quantities always having the same ratio. For example, the volume of petrol divided by its cost has the same, constant, value no matter how much petrol is involved. When two quantities x and y are proportional to each other, this can be written as y ∝ x. On a graph of y against x, they would plot as a straight line passing through the origin with gradient equal to y/x. The proportionality y ∝ x can be converted into the equation y = kx by introducing a constant of proportionality k.

Question 340

protocol/procedure/method

Answer 340

Detailed sequence of events and actions that must be carried out in order to complete a given process/experiment/investigation

Question 341

quanititative

Answer 341

Measurements or data with numbers and units attached to them, for example the number of centimetres of rain per year, are said to be quantitative.

Question 342

radiation

Answer 342

Something that spreads out from a source. See also electromagnetic radiation

Question 343

radiation sickness

Answer 343

A series of symptoms resulting from a (typically) short duration exposure to a high dose of radiation

Question 344

radon

Answer 344

A radioactive element (86Rn). When produced by the radioactive decay of uranium in rocks and the soil it is typically in gaseous form.

Question 345

rate constant

Answer 345

A constant of proportionality incorporated into rate equations describing the relationship between the rate of a chemical reaction and the concentration of one of the reactants

Question 346

rate equation

Answer 346

An equation that relates the rate of a chemical reaction to the concentration (and sometimes pressure) of the reactants

Question 347

reactant

Answer 347

A substance that takes part in a chemical reaction and whose constituent atoms appear in the product(s) of the reaction.

Question 348

recombinant

Answer 348

In biology this pertains to a piece of DNA that would not occur naturally and that has had to be made in the laboratory

Question 349

risk

Answer 349

The probability that a particular hazard will cause harm such as adverse health effects to anyone exposed to that hazard

Question 350

risk assessment

Answer 350

The process by which a planned programme of work is evaluated in terms of the hazards associated with the work and the risk of harm being experienced by individuals (including those involved in the work and others who may be in the vicinity)

Question 351

savannah

Answer 351

Type of ecosystem characterised by grassland and trees spaced widely such that the canopy does not close

Question 352

second order reaction

Answer 352

A chemical reaction the rate of which is proportional to the squared concentration of a given reactant

Question 353

sediment

Answer 353

Material derived from pre-existing rock, from biological sources, or formed by chemical processes, that is deposited at or near the Earth’s surface.

Question 354

semi-log (or log-linear) plot

Answer 354

A graphical representation in which one axis has a logarithmic scale and one axis has a linear scale

Question 355

sorting

Answer 355

A measure of the range of grain sizes present in a sediment or a sedimentary rock. If many grains fall within a narrow range of sizes, the sediment is said to be well sorted. If a wide range of grain sizes is present, a sediment is said to be poorly sorted. The degree of sorting can help to indicate the environment in which a sediment was deposited.

Question 356

spectrophotometer

Answer 356

An instrument that measures the amount of light of a specific wavelength that passes through a sample of liquid held in a cuvette

Question 357

spirilla

Answer 357

Sprial shaped bacteria (rigid)

Question 358

spirochaetes

Answer 358

Spiral shaped bacteria (flexible)

Question 359

stationary phase

Answer 359

Phase of bacterial growth in which the number of dead/dying cells in a population equals the number of new cells being added to the population

Question 360

statistically significant

Answer 360

An indication of the likelihood that a relationship observed between two groups/conditions is due to random chance

Question 361

sterile

Answer 361

Free from microorganisms

Question 362

super-saturated

Answer 362

A solution containing more dissolved material than the solvent can support in standard conditions/a vapour with a higher partial pressure than the vapour pressure of the compound

Question 363

surface area

Answer 363

The total area enclosed by all the exposed faces of a three dimensional object

Question 364

surface processes

Answer 364

The variety of processes that occur on the Earth’s surface and that can affect its physical profile, properties, composition and function

Question 365

testable

Answer 365

An inherent characteristic of all scientific theories and hypotheses that allows for them to be evaluated by someone other than the originator.

Question 366

tetanus

Answer 366

A bacterial infection of the nervous system

Question 367

theoretical physics/ theoretical physicist

Answer 367

Theoretical Physics/Theoretical Physicist
A branch of science specialised in the use of mathematical models and conceptual understanding of the laws of the universe to make predictions about and improve the understanding of phenomena in the physical world/A scientist who works in this area

Question 368

transpiration/transpire

Answer 368

The giving off of water by the leaves of a plant. Plants draw water from the soil via their roots. This water is carried up through the stems or branches to the leaves, from where it evaporates through stomata. See also evaporation

Question 369

tuberculosis

Answer 369

A contagious bacterial infection of the lungs

Question 370

tundra

Answer 370

An ecosystem characterised as largely treeless and relatively barren with limited colonisation by low level shrubs and other plants

Question 371

turbidity

Answer 371

A measure of the cloudiness (lack of transparency) in a sample of liquid

Question 372

typhoid

Answer 372

A contagious bacterial infection that can affect many organs in the body

Question 373

uncertainty

Answer 373

An estimate of the likely range of a measured quantity. For example, the length of a piece of string might be quoted as 10.2 cm ± 0.2 cm; here the uncertainty is ± 0.2 cm, which means that the length is likely to be in the range 10.0 cm to 10.4 cm.
At another level, uncertainty can describe the results of a lack of information, or disagreement about what is known (or even what is knowable).

Question 374

vapour

Answer 374

A substance in the gas phase

Question 375

variable

Answer 375

Any factor that can be changed and measured in an experiment

Question 376

vibrios

Answer 376

Comma shaped (curved) bacteria

Question 377

zero order reaction

Answer 377

A chemical reaction the rate of which is not dependent on the concentration of a given reactant.

Question 378

acceleration

Answer 378

The rate of change of velocity. In SI units acceleration is measured in metres per second per second (m s–2 ). Like velocity, acceleration has a magnitude and a direction associated with it.

Question 379

acceleration due to gravity

Answer 379

The acceleration of an object that is falling freely under the influence of a gravitational force. Usually applied to the acceleration of objects close to the Earth’s surface, where the acceleration of any freely falling object has the value g = 9.8 m s-2 irrespective of the mass of the object

Question 380

balanced force

Answer 380

a force on an object is said to be balanced if it is counteracted by a force of equal magnitude in the opposite direction

Question 381

coefficient of friction

Answer 381

The constant µ in the relation Ffric = µ N between the magnitude Ffric of the maximum frictional force on a body as it slides over a solid surface, and the magnitude N of the normal reaction force that the surface exerts on the body. The value of µ depends on the surfaces involved and their state of lubrication, but is largely independent of other factors, including the area of contact and the speed of the object.

Question 382

component

Answer 382

(of a force) The strength of a force along two directions at right angles to one another that can be used to specify a force

Question 383

continuous spectrum

Answer 383

A spectrum consisting of light (or other electromagnetic radiation) of all colours (or all photon energies, wavelengths or frequencies). The spectrum of white light from a tungsten filament light bulb is a continuous spectrum. Compare with line spectrum.

Question 384

cosine

Answer 384

The cosine of an angle θ in a right-angled triangle is defined by cos θ = adjacent / hypotenuse, where ‘adjacent’ is the length of the side next to θ and ‘hypotenuse’ is the length of the side opposite the right angle.

Question 385

coloumb

Answer 385

In SI units, the unit of electric charge, with the symbol C.

Question 386

coulombs law

Answer 386

Two particles of unlike (or like) charge, at rest, will attract (or repel) each other with an electric force that’s proportional to the product of the charges divided by the square of their separation.

Question 387

dynamic equillibrium

Answer 387

(In the context of forces) An object is in a state of dynamic equilibrium if it is acted upon by balanced forces, but is moving with a constant speed.

Question 388

electric charge

Answer 388

A fundamental property of matter. There are two types, positive and negative charge. Like charges repel each other with an electric force, and unlike charges attract each other. Objects with no charge, or with equal amounts of positive and negative charge, are electrically neutral. The SI unit of charge is the coulomb, with the symbol C. The fundamental unit of electric charge is the charge of a proton, represented by +e, which has a value of 1.6 × 10-19 C.

Question 389

electric field

Answer 389

The region where electric forces act, produced by an electric charge or by a varying magnetic field. See also Coulomb’s law.

Question 390

electric force

Answer 390

The force produced on a charged object by another electric charge. The electric force between two charged objects depends on Coulomb’s law.

Question 391

electromagnetic interaction

Answer 391

One of the four fundamental interactions. In most situations it is adequately described by Maxwell’s laws of electromagnetism. However, by incorporating the effects of quantum physics and Einstein’s special theory of relativity, the modern theory of QED provides a better description on very small size scales and in high-energy situations. It explains interactions between particles that possess electric charge in terms of the exchange of quanta called photons. It unifies all electric, magnetic and radiation phenomena into a single theory. Electromagnetic interactions get stronger with increasing energy of interaction.

Question 392

equillibrium

Answer 392

For the purpose of this module, an object is said to be in equilibrium if it is acted upon by either no force or balanced forces. Thus, an object in equilibrium remains at rest or moves with a constant speed. See dynamical equilibrium and static equilibrium.

Question 393

force

Answer 393

A disturbance that tends to accelerate an object. Forces can negate the effects of other forces, so acceleration will ensue only if an unbalanced force acts on a body. In SI units, the unit of force is the newton (N).

Question 394

free-body diagram

Answer 394

A diagram used in the analysis of a set of objects that shows only the object of interest and the forces that act upon it.

Question 395

frictional force

Answer 395

The force that arises when relative motion occurs or is tending to occur between two solid bodies that are in contact. (See coefficient of friction)

Question 396

gradient (of a graph)

Answer 396

The slope of a line on a graph, given by the change in vertical position (the rise) between two points divided by the corresponding change in horizontal position (the run). If the coordinates of two points on a straight line are (x1, y1) and (x2, y2) then the gradient of the graph is: gradient y y x x rise run 2 1 2 1 = = - - (

Question 397

gravity

Answer 397

The natural phenomena that gives rise to a force that causes any object (with mass) to be attracted to any other object (with mass). In colloquial speech, the term is used to describe the attraction of objects on or near the Earth’s surface towards the centre of the Earth.

Question 398

magnitude (of a force)

Answer 398

The size of a force

Question 399

mass

Answer 399

The measure of the quantity of matter in an object. In SI units, the unit of mass is the kilogram. The mass of a body determines its acceleration 47 when it is acted on by an unbalanced force; the greater the mass (for a given unbalanced force) the smaller the acceleration. The quantitative relationship is given by Newton’s second law of motion F = ma. Mass is also a measure of the inertia of a body. Mass also determines the magnitude of the gravitational force acting on a body. This gravitational force is also known as the weight of the body. Mass and energy are related by Einstein’s equation E = mc2.

Question 400

maximum frictional force

Answer 400

The largest frictional force, defined as the product of the coefficient of friction and the normal reaction force.

Question 401

maxwells laws of electromagnetism

Answer 401

A theory unifying the phenomena of electric and magnetic interactions, as they were understood towards the end of the 19th century. The theory explains that stationary electric charges give rise to electric fields, that moving electric charges (i.e. electric currents) give rise to magnetic fields, that a changing magnetic field produces an electric field, and that a changing electric field produces a magnetic field. A prediction of Maxwell’s theory was the existence of electromagnetic Glossary 48 radiation which travels through space at the speed of light. Compare with quantum electrodynamics.

Question 402

normal reaction force

Answer 402

When an object rests on (or is pressed into) a solid surface, the solid is compressed slightly. The solid resists compression by exerting a force on the object. This reactive force acts at right-angles to the surface at the point of contact, and is therefore called a normal reaction force.

Question 403

resolving forces

Answer 403

The process of finding a force’s components, along specified directions, from the magnitude and direction of the force.

Question 404

sine

Answer 404

The sine of an angle θ in a right-angled triangle is defined by sin θ = opposite / hypotenuse, where ‘opposite’ is the length of the side opposite θ and ‘hypotenuse’ is the length of the side opposite the right angle.

Question 405

speed

Answer 405

The rate at which a distance is travelled. In SI units speed is measured in metres per second (m s−1). Note speed is the magnitude of velocity.

Question 406

spring constant

Answer 406

The constant ks that relates the spring force Fstr and the extension x for an ideal spring that obeys Hooke’s law; Fstr = −ks x.

Question 407

static equillibrium

Answer 407

(In the context of forces) An object is in a state of static equilibrium if it is acted upon by balanced forces, and is at rest.

Question 408

tension

Answer 408

An object is in a state of tension when a force acts on it in such a way as to increase its length.

Question 409

unbalanced force

Answer 409

A force which is not counteracted by a force of equal magnitude in the opposite direction, and hence causes the acceleration of an object.

Question 410

weight

Answer 410

A physical property that quantifies the strength of the gravitational force acting on a body which has a certain mass. Mass m is related to weight Fg by the equation Fg = mg, where g is the acceleration due to gravity. The term weight is often used colloquially in contexts where the correct scientific term is mass.

Question 411

absolute zero

Answer 411

The lowest temperature that can be attained, 0 K or −273.18°C

Question 412

dynamo

Answer 412

A device that turns mechanical motion into electrical current.

Question 413

heat

Answer 413

The transfer of energy from one object to another that occurs because of a temperature difference between the two. Heat is always transferred from hot to cold.

Question 414

kelvin

Answer 414

The SI unit of temperature, symbol K

Question 415

negative ion

Answer 415

(or anion) An atom or molecule that has gained one or more electrons, and as a result carries a negative charge.

Question 416

positive ion

Answer 416

(or cation) An atom or molecule that has lost one or more electrons, and as a result carries a positive charge.

Question 417

potential difference

Answer 417

When a charge of 1 C is moved from one location to another a potential difference of 1 V, the quantity of work done on the charge is 1 J.

Question 418

potential energy

Answer 418

The energy associated with the presence of a force.

Question 419

power

Answer 419

The rate at which energy is transferred from one thing to another. Power is measured in watts (W), and 1 W is 1 J s−1

Question 420

pressure

Answer 420

A measure of the force per unit area.

Question 421

SI base unit system

Answer 421

In the SI unit system, there are seven base units; all other units can be expressed in terms of the base units. The base units are:

Mass - kilogram - kg
Time - second - s
Distance - metre - m
Amount of substance - mole - mol
Electric current - amp - A
Temperature - Kelvin - K
Luminous intensity - Candela - cd

Question 422

SI derived unit

Answer 422

An SI derived unit i a unit formed by combining the SI base units (always through multiplication or division of powers of the base units). For example a 1 joule (J) is equivalent to 1 kg m2 s−1.

Question 423

temperature

Answer 423

A measure of the hotness of an object. In SI unit temperature is measured in kelvin (K).

Question 424

thermal energy

Answer 424

The energy associated with temperature. Microscopically, the thermal energy is the sum total of the random (kinetic) energy of the atoms and molecules that comprise a substance.

Question 425

volt

Answer 425

The unit of potential difference. Moving a charge of one coulomb through a potential difference of 1 V.

Question 426

work

Answer 426

The amount of energy transferred from one thing to another by the action of a force. The quantity of work done W (in J) by a force F (in N) applied to move an object through a distance d (m) is W = F × d.

Question 427

atomic number

Answer 427

The number of protons within the nucleus of an atom; it is also equal to the number of electrons in the neutral atom. Each chemical element has a unique, characteristic atomic number.

Question 428

chemical bonding

Answer 428

The means by which atoms are attached to each other. For example, in a water molecule an oxygen atom is attached to each of two hydrogen atoms by chemical bonding.

Question 429

chemical element

Answer 429

A substance that consists of only one type of atom. For example, the chemical element copper is made only of copper atoms. A chemical element cannot be broken down into simpler constituents by using chemical reactions. All the atoms in a sample of a chemical element have the same atomic number.

Question 430

chemical formula

Answer 430

A representation of a chemical substance that uses chemical symbols to denote the constituent atoms, and subscripts to indicate the relative numbers of atoms of each type. For example, water is represented by the formula H2O.

Question 431

conductors

Answer 431

Conductors are materials that allow a transfer of energy. Conductors of electricity allow the flow of charged particles. Conductors of heat allow the transfer of thermal energy.

Question 432

covalent bond

Answer 432

A type of chemical bond in which a pair of electrons are shared between two atoms.

Question 433

diatomic molecule

Answer 433

A covalently bonded molecule containing just two atoms bonded together.

Question 434

ductile

Answer 434

Materials that are easily drawn into wires.

Question 435

electron

Answer 435

(e-) One of the component particles from which an atom is made. Electrons have a negative electric charge, and they surround the atom’s positively charged nucleus. Electrons carry the electric current in metals.

Question 436

electron conductor

Answer 436

A material through which an electric current will flow

Question 437

electron configuration

Answer 437

The arrangement of electrons in an atom (or molecule).

Question 438

giant covalent structure

Answer 438

A substance where many atoms are covalently bonded in a regular three-dimensional array, but with no defined size.

Question 439

group

Answer 439

A set of chemical elements, commonly placed in a vertical column in the Periodic Table, having related chemical properties

Question 440

hydrocarbons

Answer 440

Covalent compounds containing atoms of carbon and hydrogen only.

Question 441

ionic interactions

Answer 441

The electrostatic attractive forces between positively charged ions and negatively charged ions.

Question 442

ions

Answer 442

An atom or a molecule or a chemical group that has lost or gained one or more electrons, leaving it with a positive or negative electric charge

Question 443

malleable

Answer 443

Materials that can be beaten into shape.

Question 444

neutron

Answer 444

One of the two types of particle found in the nucleus of an atom. The neutron has zero electric charge and a mass very close to that of the proton. As with the proton therefore, the relative atomic mass of a neutron is very close to unity on the scale of relative atomic masses.

Question 445

noble gases

Answer 445

The gaseous chemical elements helium, neon, argon, krypton, xenon and radon, which are all placed in Group 18 of the Periodic Table. These elements do not readily form chemical compounds with other elements.

Question 446

periodic table

Answer 446

An arrangement of elements which organises them in order of increasing atomic number across several rows known as periods. The vertical groups contain elements with related properties.

Question 447

proton

Answer 447

The nucleus of the hydrogen atom and one of two constituents of all other nuclei; the particle has a relative mass very close to unity on the scale of relative atomic masses. They are positively charged.

Question 448

amplitude

Answer 448

(of a wave) Half the peak-to-trough displacement of a wave

Question 449

de broglie wavelength

Answer 449

The wavelength associated with the propagation of a ‘particle’ through space. Named for Louis de Broglie, who first suggested that all particles move from place to place with wave-like properties, and so exhibit wave–particle duality.

Question 450

electromagnetic spectrum

Answer 450

The entire range of electromagnetic radiation from radio waves, through microwaves, infrared radiation, light, ultraviolet (UV) radiation, and X-rays to gamma-rays. All electromagnetic radiation propagates as waves with the speed of light c = 3.00 × 108 m s–1, but interacts with matter (i.e. is emitted or absorbed) as a stream of particles, called photons.

Question 451

electronvolt

Answer 451

A unit of energy corresponding to the energy converted when an electron moves from one terminal of a 1 V battery to the other. Numerically it is equal to 1.602 × 10–19J. The energy of photons of light is conveniently expressed in units of electronvolts, but the energy of a fundamental particle is usually expressed in MeV (106eV) or GeV (109eV).

Question 452

excited state

Answer 452

Any quantum state that’s not the ground state.

Question 453

exclusion principle

Answer 453

A rule of quantum physics, described by Wolfgang Pauli, which forbids any two electrons in the same atom from occupying the same quantum state.

Question 454

frequency

Answer 454

(of a wave) The number of complete cycles of a wave that pass a certain fixed point in a unit of time. Conventionally measured in the SI unit of hertz, Hz (or, equivalently, s-1). It is equal to one over the period of the wave, f=1/t, and is related to the wavelength λ and the speed of a wave by v = f λ.

Question 455

ground state

Answer 455

The lowest energy arrangements of electrons in an atom (or molecule). The quantum state that corresponds to the lowest energy level of an atom, or other quantum system.

Question 456

heisenberg uncertainty principle

Answer 456

A fundamental result of quantum physics, discovered by Werner Heisenberg, that rules out the possibility of combining definite knowledge of some quantities (such as position) with definite knowledge of certain other quantities (such as velocity). It also limits the precision with which certain quantities can be measured simultaneously.

Question 457

hydrogen-like ions

Answer 457

Any ion which, like hydrogen, has only a single electron bound to its nucleus. Examples include He+, Li2+ and Be3+. The energy levels of hydrogen-like ions resemble those of hydrogen itself, merely scaled in energy by the atomic number squared.

Question 458

indeterminancy

Answer 458

A characteristic feature of quantum physics which refers to the fact that the behaviour of an individual quantum system cannot be predicted in advance, and that the positions, speeds and other attributes of quantum systems cannot be precisely known in combination.

Question 459

interference

Answer 459

The phenomenon arising when two waves meet. Constructive interference is the phenomenon whereby two waves combine to produce a wave with a larger amplitude than either of the original oscillations or waves. Destructive interference is the phenomenon whereby two waves combine to produce a wave with a smaller amplitude than either of the original oscillations or waves.

Question 460

madelung rule

Answer 460

A rule used to determine the approximate order in which orbitals are filled in atoms.

Question 461

magnetic quantum number

Answer 461

A quantum number represented by the symbol mlused when labelling quantum states. It may take values between –l and +l, where l is the orbital quantum number.

Question 462

nanometre

Answer 462

A unit of distance corresponding to 10-9 m. Different colours of visible light have a wavelength of a few hundred nanometres

Question 463

neutrino

Answer 463

A subatomic particle with no charge that interacts weakly with matter

Question 464

newton

Answer 464

In SI units, the newton is the unit of force, symbol N, and is equivalent to kg m s–2 .

Question 465

newtons first law of motion

Answer 465

This law states that an object remains at rest or moves in a straight line at constant speed unless it is acted on by an unbalanced force.

Question 466

newtons second law of motion

Answer 466

This law states that the magnitude F of the unbalanced force on an object with a mass m is related to the magnitude a of the acceleration of the object by the equation F = ma, the acceleration being in the same direction as the unbalanced force.

Question 467

orbital quantum number

Answer 467

The number l used to label the subshells within a given shell of electrons. When labelling quantum states it may take any value from 0 up to n–1, where n is the principal quantum number.

Question 468

orbitals

Answer 468

The word orbital is used to describe the waveforms that electrons make in hydrogen and other atoms.

Question 469

period

Answer 469

In physics, the interval of time it takes for a single complete cycle of a wave to pass a fixed point. Symbol: T. Equal to one over the frequency of a wave. T = 1/f

Question 470

photon

Answer 470

A particle of light or other electromagnetic radiation. Photons of the same frequency have exactly the same amount of energy, called a quantum of energy. Photons have no mass or electric charge and do not experience the electromagnetic interaction.

Question 471

planck constant

Answer 471

The fundamental constant relating to quantum mechanics. It has the value h = 6.63 × 10−34 J s, or 4.14 × 10−15 eV Hz−1. The Planck constant is defined by the equation Eph = hf linking energy of photons with frequency.

Question 472

principal quantum number

Answer 472

The number n used to characterise the major electron shells of an atom

Question 473

probability

Answer 473

The quantitative value for the chance or likelihood that a given outcome will occur. Probabilities have values between 0 and 1. A probability of 1 indicates a certainty; a probability of 0 indicates an event which will never occur.

Question 474

quantum

Answer 474

(plural: quanta)
1. The amount of energy carried by a single photon of light or other electromagnetic radiation.

2. Used to refer to any system in which energy levels exist, and which therefore emit or absorb quanta of light, and/or in which the constituent particles have indeterminate positions and speeds.

Question 475

quantum mechanics

Answer 475

A theory of the behaviour of small objects with three important ideas: objects have wave−particle duality, have fixed amounts of energy known as quanta, and are governed by the laws of chance.

Question 476

quantum number

Answer 476

One of a set of (up to four) numbers used to describe the quantum state of an atom or other quantum system.

Question 477

quantum state

Answer 477

A description of the properties of an atom or other quantum system. In general, each energy level of an atom will correspond to more than one quantum state.

Question 478

quantum system

Answer 478

A system of particles which are bound together and so exhibit quantised energy levels. Nuclei, atoms and molecules are all examples of quantum systems.

Question 479

schrodinger model of the atom

Answer 479

The fully quantum model of the atom, based on the equation developed by Erwin Schrödinger.

Question 480

screening

Answer 480

Screening is the process by which electrons in orbitals close to the nucleus reduce or screen the positive charge associated with the nucleus. Screening modifies the energy of electrons in orbitals further from the nucleus.

Question 481

spectrum

Answer 481

A display (such as a graph or a photograph) of the distribution of light or other types of radiation versus the wavelength (or frequency or energy) of the radiation. It indicates the intensity of light at each different wavelength. A spectrum may be a continuous spectrum or may show emission lines or absorption lines.

Question 482

spin quantum number

Answer 482

A quantum number represented by the symbol ms used when labelling quantum states. It may take values of -1/2 or 1/2 only

Question 483

standing waves

Answer 483

A wave that does not travel

Question 484

wave

Answer 484

A periodic (regularly repeating) disturbance that transports energy from one place to another. Characterised by its wavelength, frequency (or period) and amplitude.

Question 485

waveform

Answer 485

The shape of a wave

Question 486

wavelength

Answer 486

The distance between one part of the wave profile, at a particular instant in time, and the next identical part of the wave profile at the same instant in time. Two adjacent crests of the wave are a convenient pair of locations to use for this definition, although any pair of similar points will do. Wavelength λ is related to frequency f and speed v of a wave by v = fλ

Question 487

wave-particle duality

Answer 487

Used to describe the fact that light and other forms of electromagnetic radiation travel from place to place like a wave but interact with matter as if it is composed of a stream of particles called photons. Similarly, electrons and other subatomic particles also propagate like waves but interact like particles.

Question 488

acid

Answer 488

A substance that donates protons.

Question 489

avogadros constant

Answer 489

The number of units that are present in one mole of a substance. It has the value 6.02 × 1023 mol–1.

Question 490

balanced chemical equation

Answer 490

A symbol chemical equation where the total number of each type of reactant atom is equal to the total number of each type of product atom.

Question 491

chemical change

Answer 491

A change to a substance that leads to a modification of its chemical composition.

Question 492

complex carbohydrate

Answer 492

Carbohydrates consisting of many sugar units (polysaccharides).

Question 493

curly arrows

Answer 493

A representation used in reaction mechanisms to show the movement of electrons.

Question 494

deposition

Answer 494

The direct conversion of a gas (vapour) into a solid without passage through a liquid phase.

Question 495

disaccharide

Answer 495

A molecule formed by the combining of two monosaccharides. An example is sucrose.

Question 496

dissociation

Answer 496

The process where a covalent bond is broken.

Question 497

functional group

Answer 497

In many reactions of organic compounds, only certain groups of atoms are directly involved. It is the nature of these groups of atoms that primarily determines the type of reaction that takes place, and the particular chemical properties of an organic molecule. Such groups of atoms are called functional groups.

Question 498

hydrated ions

Answer 498

Positive or negative ions that interact with several water molecules. They are formed when an ionic substance is dissolved in water.

Question 499

molar mass

Answer 499

The mass of one mole of a substance.

Question 500

mole

Answer 500

The amount of a species that contains Avogadro’s constant of that species. Its mass is obtained by adding up the relative atomic masses of the atoms in the formula unit.

Question 501

monosaccharide

Answer 501

A sugar that cannot be broken down to anything simpler. Common monosaccharides are glucose, fructose and ribose.

Question 502

organic chemistry

Answer 502

The branch of chemistry that deals with the properties and reactions of carbon-based compounds.

Question 503

partial changes

Answer 503

Charges obtained by atoms due to the unequal sharing of a bonding electron density as a consequence of electronegativity differences between bonded atoms.

Question 504

phospholipid

Answer 504

A major component of cell membranes, based on a glycerol unit that contains two water-immiscible hydrocarbon chains together with a third, charged, water-miscible group linked to the glycerol unit through a phosphate group. Phospholipids, together with proteins, are the key components of biological membranes.

Question 505

pH scale

Answer 505

A scale that provides a convenient measure of the acidity of an aqueous solution. The lower the pH, the more acid the solution. A pH of 7 corresponds to a neutral solution.

Question 506

physical change

Answer 506

A change which alters the physical nature of a substance without changing its chemical composition.

Question 507

polar bond

Answer 507

A covalent bond in which the bonding electrons are not evenly distributed due to electronegativity differences between the bonded atoms.

Question 508

reaction mechanism

Answer 508

A step-by-step series of events that explain how reactant molecules are converted into product molecules.

Question 509

relative formula mass

Answer 509

The sum of the relative atomic masses of the atoms found in the chemical formula of a substance.

Question 510

simple carbohydrate

Answer 510

Carbohydrates consisting of one sugar unit (monosaccharides) or two sugar units (disaccharides).

Question 511

skeletal formula

Answer 511

A shorthand method of representing molecular structures that shows the basic framework of the structure, together with the important atom groupings, without showing all the atoms present.

Question 512

state symbols

Answer 512

Symbols that represent and describe the physical state of a substance.

Question 513

strong acid

Answer 513

An acid that, when dissolved in water, is completely dissociated into aqueous hydrogen ions, H+(aq), and the accompanying aqueous negative ions.

Question 514

sublimination

Answer 514

The direct conversion of a solid into a gas (or vapour) without passage through a liquid phase.

Question 515

weak acid

Answer 515

An acid that, when dissolved in water, is only partly dissociated into aqueous hydrogen ions, H+ (aq), and the accompanying aqueous negative ions

Question 516

aqueous solubility

Answer 516

The ability of a substance to dissolve in water

Question 517

bond enthalpy

Answer 517

The energy required to break a bond

Question 518

compound

Answer 518

The name given to a substance made up from two or more different types of atom

Question 519

dicoordinate

Answer 519

Bonded to two other atoms

Question 520

dipole

Answer 520

The separation of a pair of positive and negative charges across a distance

Question 521

electronegativity

Answer 521

A measure of the ability of an atom to attract electrons to itself when forming chemical bonds.

Question 522

element

Answer 522

The name given to a substance made up from one type of atom

Question 523

enthalpy of vaporisation

Answer 523

The energy change required to vaporise a substance from the liquid to the gaseous state

Question 524

hydrophobic

Answer 524

Having poor solubility in water

Question 525

isomers

Answer 525

Compounds that have the same molecular formula but different structural formula.

Question 526

lewis structures

Answer 526

The dot-cross diagrams that represent the electron sharing involved in covalent bonding between atoms

Question 527

london forces

Answer 527

The weak interaction between molecules that results from the temporary unequal sharing of electrons in a covalent bond.

Question 528

lone pair electrons

Answer 528

Electrons that have paired up but are not used for bonding to another atom (also known as ‘non-bonding electron pairs’). Lone pair electrons are present on atoms from groups 15, 16 and 17 of the Periodic Table.

Question 529

molecule

Answer 529

A group of atoms covalently bonded together that is the smallest unit of a substance which gives rise to the chemical and physical properties of that substance.

Question 530

non-bonding electron pairs

Answer 530

Electrons that have paired up but are not used for bonding to another atom (also known as ‘lone pair electrons’). Non-bonding electron pairs are present on atoms from groups 5, 6 and 7 of the Periodic Table.

Question 531

non-ionic surfactant

Answer 531

Uncharged compounds that contain both a water-soluble component and an oil-soluble component

Question 532

relative atomic mass

Answer 532

The ratio of the mass of an atom of an element to 1/12th of the mass of the carbon-12 isotope

Question 533

relative molecular mass

Answer 533

The sum of the relative atomic masses of all the constituent atoms in a molecule

Question 534

surfactant

Answer 534

A compound that has both polar and non-polar regions in its molecular structure, such that it can interact with both polar and non-polar materials

Question 535

tetracoordinate

Answer 535

Bonded to four other atoms

Question 536

tricoordinate

Answer 536

Bonded to three other atoms

Question 537

valency

Answer 537

The number of shared electron-pair bonds that an atom must form if it is to attain an electronic structure with a full outer shell of electrons.

Question 538

3’

Answer 538

Describes one of two key carbon atoms in nucleotide ribose sugars that are involved in the polymerisation of nucleotides to form nucleic acids. Pronounced ‘three prime’.

Question 539

3’ end

Answer 539

One of the two ends of a nucleic acid molecule, corresponding to the position of the 3’ carbon within the ribose sugars of that nucleic acid.

Question 540

5’

Answer 540

Describes one of two key carbon atoms in nucleotide ribose sugars that are involved in the polymerisation of nucleotides to form nucleic acids. Pronounced ‘five prime’.

Question 541

5’ end

Answer 541

One of the two ends of a nucleic acid molecule, corresponding to the position of the 5’ carbon within the ribose sugars of that nucleic acid. Considered the start of the molecule.

Question 542

adenine

Answer 542

One of the four chemical bases used in DNA, and one of the four bases used in RNA.

Question 543

amino acids

Answer 543

Chemical monomers that make proteins.

Question 544

antiparallel

Answer 544

Adjective used to describe the strands in a double-stranded DNA molecule, which run in parallel to each other but in opposite directions.

Question 545

antisense strand

Answer 545

(or noncoding strand or template strand) Terms used during gene transcription to describe the strand of chromosomal DNA that is used as the template and whose sequence is complementary to the mRNA molecule produced.

Question 546

base

Answer 546

Chemical groups that are one of the component parts of a nucleotide, together with phosphate and a ribose sugar.

Question 547

base pairing

Answer 547

Hydrogen bonding between complementary nucleotides that allows DNA to become double stranded.