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Chemistry > Definitions > Flashcards

Definitions Flashcards

1
Q

Daltons atomic theory

A

All matter is made up of very small particles called atoms

All atoms are indivisible. They cannot be broken down into smaller particles.

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2
Q

Cathode rays

A

Streams of negatively charged particles called electrons.

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3
Q

Energy level

A

The fixed energy value an electron can have in an atom

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4
Q

Ground state

A

State where an electron occupies lowest energy level available

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5
Q

Excited state

A

State where an electron occupies a higher energy level than those available in the ground state

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6
Q

Heisenbergs uncertainty principle

A

It is not possible to measure at the same time both the velocity and position of an electron in an atom

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7
Q

Orbital

A

Fixed region of space where there is a high probability of finding an electron

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8
Q

Sub level

A

A subdivision of a main energy level that consists of one or more orbitals of the same energy

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9
Q

Element

A

Substance that cannot be split into simpler substances by chemical means

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10
Q

Dobereiners triad

A

A triad is a group of 3 elements with similar properties in which the atomic weight of the middle element is approximately equal to the average of the other two

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11
Q

Newlands octaves

A

The arrangement of elements in which the first and eight elements counting from a particular element have similar properties

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12
Q

Mendeleevs Periodic law

A

When elements are arranged in order of increasing atomic weight, the properties of the elements recur/ repeat periodically in columns (groups) of similar chemical properties

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13
Q

Atomic number

A

Number of protons in the nucleus of an atom

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14
Q

Modern periodic law

A

When elements are arranged in order of increasing atomic number the properties of the elements recur/repeat periodically

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15
Q

Mass number

A

Sum of the number of protons and neutrons in the nucleus of an atom of that element

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16
Q

Isotopes

A

Atoms of the same element so they have the same atomic number due to the same number of protons but differing mass number due to the different number of neutrons in the nucleus

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17
Q

Relative atomic mass

A

The average mass number of the isotopes of an element as they occur naturally taking their abundance’s into account and expressed on a scale in which the atoms of the carbon 12 isotope have a mass of exactly 12 units

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18
Q

Principle of mass spectrometry

A

Charged particles moving in a magnetic field are deflected and separated by different extents/ amounts according to their masses

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19
Q

Electron configuration

A

Shows the arrangement of electrons in an atom of an element

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20
Q

Aufbau principle

A

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

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21
Q

Hunds rule of maximum multiplicity

A

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

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22
Q

Paulis exclusion principle

A

No more than two electrons can occupy and orbital and the electrons must have opposite spin

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23
Q

Compound

A

Substance that is made up of two or more different elements that are chemically combined e.g. Water, carbon dioxide, ammonia, methane

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24
Q

Octet rule

A

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

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25
Q

Ion

A

Charged atom or group of atoms

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26
Q

Ionic bond

A

Force of attraction between oppositely charged ions in a compound
Always formed by the complete transfer of electrons from one atom to another

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27
Q

Transition metal

A

Metal that forms at least one ion with a partially filled d sub level

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28
Q

Molecule

A

Group of atoms joined together.

Smallest particle of an element or compound that can exist independently

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29
Q

Valency

A

Number of atoms of hydrogen or any other monovalent element with which each atom of the element combines

E.g. carbon can bond to 4H atoms so it has a valency of 4

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30
Q

Sigma bond

A

Formed by the head on overlap of molecular orbitals

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31
Q

Pi bond

A

Formed by the sideways overlap of p,d and forbitals

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32
Q

Electronegativity

A

Relative attraction an atom in a molecule has

For the shared pair of electrons in a covalent bond

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33
Q

Polar Covalent Bond

A

A polar covalent bond is a bond in which there is unequal sharing of the pair of electrons. This causes one end of the bond to be partially positive and the other end to be partially negative.

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34
Q

Intramolecular Bonding

A

Bonding that takes place within a molecule.

It holds atoms in a molecule together
E.g covalent bonding

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35
Q

Intermolecular Forces

A

Forces of attraction between different molecules

E.g Van der Waals, hydrogen bonding,dipole-dipole

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36
Q

VAn der Waals

A

Weak forces of attraction between molecules //

Resulting from the formation of temporary dipoles.

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37
Q

Dipole-dipole Forces

A

Forces of attraction between the negative pole of one polar molecule
And the possitive pole of another polar molecules.

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38
Q

Hydrogen Bond

A

Particular dipole-dipole attractions between molecules where the hydrogen atom bonded to either nitrogen, fluorine or oxygen.
The H atom carries a partial positive charge and is attracted to a partial negative charge in a nearby polar molecule.

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39
Q

Half-life

A

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

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40
Q

Law of Conservation of Matter

A

The law of conservation of matter states that in any chemical reaction matter is neither creatednor destroyed, but merley changed from one form to another.

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41
Q

Atomic Radius

A

Half the distance between the nuclei of two atoms of the same element
That are joined together by a single covalent bond.

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42
Q

First Ionisation Energy

A

Minimum energy required to completely remove the most loosely bound electron //
From a neutral gaseous atom in its ground state
E.g Na (g) - Na +(g)+e

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43
Q

Second Ionisation Energy

A

Energy required to completely remove an electron from an ion with positive charge
In the gaseous state
E.g Ca+(g)-Ca+2(g)+e

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44
Q

Radioactivity

A

Spontaneous breaking up of unstable nucleiWith the emission of one or more types of radiation

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45
Q

Nuclear Reaction

A

Process that alters the composition, structure or energy of an atomic nucleus.

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46
Q

Mole

A

Is an amount used in chemistry

A mole of a substance is the amount of that substance that contains 6x10 (23) particules of that substance.

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47
Q

Relative molecular mass (RMM)

A

Average mass of one molecule of that compound compared with one twelfth the mass of one atom of the carbon-12 isotape.

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48
Q

Gas

A

Substance that has no well-defined boundary

But diffuses rapidly to fill the container in which it is pleased.

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49
Q

Boyle’s Law

A

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

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50
Q

Charles Law

A

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

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51
Q

Gay-Lussac’s Law of Combining Volumes

A

In a reaction between gases, the volume of the reacting gases and the volumes of any gaseous products are in the ratio of small whole numbers
Provided the volumes are measured at the same temperature and pressure.

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52
Q

Avogadro’s Law

A

Equal volumes of gases contain equal numbers of molecules under the same conditions of temperature and pressure.

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53
Q

Ideal Gas

A

A Gas that perfectly obeys all of the assumptions of the kinetic theory of gases under all conditions of temperature and pressure.

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54
Q

Real Gases

A

Different from am ideal gasbecause forces of attraction and repulsion do exist between molecules and The volume of the molecules is not always negligible.

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55
Q

Molecular formula

A

The formula which shows the number and type of each atom present in a molecule of that compound

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56
Q

Empirical formula

A

This is the simplest whole number ratio of atoms or ions of each element in a substance

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57
Q

Arrhenius’s acid

A

Substance that dissociates in water go from H+ ions

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58
Q

Arrhenius’s base

A

Substance that dissociates in water to form OH- ions

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59
Q

Arrhenius’s strong vs weak acid

A

Strong acid: almost completely dissociates in water to from H+ ions

Weak acid: slightly dissociates in water to form H+ ions

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60
Q

Arrhenius’s strong vs weak base

A

Strong base: almost completely dissociates in water to form OH- ions

Weak base: slightly dissociates in water to form OH-ions

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61
Q

Brønsted-Lowry acid, strong acid, weak acid

A

Acid = proton donor
Strong acid=good proton donor
Weak acid = poor proton donor

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62
Q

Conjugate acid base pair

A

Any pair consisting of an acid and a base that differ by a proton.
An acid becomes its conjugate base after it has donated a proton.

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63
Q

Salt

A

Substance formed when a hydrogen ion from an acid is replaced by a metal or an ammonium ion

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64
Q

Neutralisation

A

Reaction between an acid and a base to produce a salt and water

65
Q

Solution

A

Completely perfect mixture of a solute and a solvent.

In a solution, the solute particles are uniformly distributed throughout the solvent I.e. the solution is homogenous

66
Q

Concentration

A

Amount of solute dissolved in a given volume of solution

67
Q

Standard solution

A

Solution which concentration is accurately known

68
Q

Primary standard

A

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

69
Q

Titration

A

An experiment, the measured volume of one solution is added to the known volume of another solution until the reaction is complete
Usually Indicated with a colour change (If an indicator is present)

70
Q

Oxidation

A

Oxidation is loss of electrons.

Increase in oxidation number

71
Q

Oxidising agent

A

Substance that causes something else to be oxidised.

The oxidising agent itself will be reduced

72
Q

Reduction

A

Reduction is loss of electrons

Decrease in oxidation number

73
Q

Reducing agent

A

Substance that causes something else to be reduced

The reducing agent itself will be oxidised

74
Q

Oxidation number

A

Charge that an atom has or appears to have after electrons have been distributed according to certain rules

75
Q

Rate of reaction

A

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

Or

Change in concentration
————————————
Time

76
Q

Instantaneous rate of reaction

A

Rate of reaction at any one particular time during a reaction

77
Q

Catalyst

A

Substance that alters the rate of a chemical reaction but is not consumed in the reaction

78
Q

Enzyme

A

Substance that is produced by a living cell and acts as a biological catalyst

79
Q

Homogenous catalysis

A

Catalysis in which both the reactants and the catalyst are in the same phase (I.e. there is no boundary between the reactants and the catalyst)

KEY:PHASE IS NOT THE SAME AS STATE. DO NOT SAY STATE

80
Q

Heterogeneous catalysis

A

Catalysis in which both the reactants and the catalyst are in different phases (I.e. there is a boundary between the reactants and the catalyst)

81
Q

Autocatalysis

A

Catalysis in which one of the products of the reaction acts as a catalyst for the reaction

82
Q

Catalytic converter

A

Device that is fitted to the exhaust system of a motor vehicle which contain catalysts to convert pollutants in the exhaust gases to less harmful substances

83
Q

Catalytic poison

A

Substance that makes a catalyst inactive by sticking to the surface of the catalyst, blocking the active site

84
Q

Effective collision

A

Collision that results in the formation of products

85
Q

Activation energy

A

Minimum energy that colliding particles must have in order for a chemical reaction to occur

86
Q

Reaction profile diagram

A

Graph which shows the change in energy of a chemical reaction over time as the reaction progresses

87
Q

Reversible reaction

A

One in which the products react to give back the reactants I.e. the reaction is going in both directions

88
Q

Chemical equilibrium

A

State of dynamic balance in a reversible reaction where the rate of forward reaction is equal to the rate of reverse reaction

89
Q

Dynamic state

A

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

90
Q

Dynamic equilibrium

A

Rate of forward reaction is equal to the rate of the reverse reaction

91
Q

Le chateliers principle

A

If a stress is applied to a system in equilibrium, the system readjusts to relieve the stress applied

92
Q

Equilibrium constant (Kc) for Haber Bosch reaction

A

N2 + 3H2 2NH3

Kc= [NH3]2
———-
[N2][H2]3

93
Q

Self ionisation of water/ ionic product of water (Kw)

A

H2O H+ + OH-

Kw = [H+][OH-]

Key: never write H2O in the Ka, Kb, Kw expressions

94
Q

pH

A

pH= -log10[H+]

95
Q

Dissociation of an acid (HCL) in water

A

HCL + H2O H3O+ + Cl-

96
Q

Acid dissociation constant (Ka)

A

HCL + H2O H3O+ Cl-
Ka =[H3O+][Cl-]
—————-
[HCl]

97
Q

pOH

A

pOH = -log10[OH-]

98
Q

Acid- base indicator

A

Substance that changes colour according to the pH of the solution in which it is placed

99
Q

Indicator range

A

pH interval over which there is a clear change in colour for that indicator

100
Q

Hard water

A

Water that does not form a lather easily with soap. Forms a scum instead

Caused by Mg+2 or Ca+2 ions

101
Q

Temporary hardness

A

Hardness that can be removed by boiling

Caused by the presence of calcium hydrogencarbonate

102
Q

Permanent hardness

A

Hardness that cannot be removed by boiling

Caused by the presence of magnesium sulphate

103
Q

Buffer solution

A

Solution that resists changes in pH. It keeps the pH of a solution constant

104
Q

Flocculation

A

Coagulation of small suspended particles in water, to form larger particles which settle to the bottom of the tank

105
Q

B.O.D Biochemical Oxygen Demand

A

BOD is the amount of dissolved oxygen in p.p.m consumed by biological action, when a sample of water is stored in the dark at 20•C for 5 days

106
Q

Eutrophication

A

Enrichment of water with nutrients which leads to excessive growth of algae and other plants

107
Q

Primary treatment of sewage

A

Mechanical process in which large solids are removed by screening and some suspended solids are removed by sedimentation

108
Q

Secondary treatment of sewage

A
  • Biological oxidation process where the levels of suspended and dissolved organic material is reduced
  • sewage is decomposed by bacteria which use nutrients from the sewage together with oxygen from the air to break down the sewage
109
Q

Tertiary treatment of sewage

A
  • process involving the removal of phosphorus compounds by precipitation
  • and the removal of nitrogen compounds by biological ion-exchange methods
110
Q

Principle of colorimetry

A

Amount of absorbance of light by a coloured solution is proportional to the concentration of the solution

111
Q

Electrolysis

A

Use of electricity to make a chemical reaction happen in an electrolyte

112
Q

Electrolyte

A

Compound, when molten or dissolved in water, will conduct an electric current

113
Q

Electroplating

A

An electrolyte is used to put a layer of one metal on the surface of another metal

114
Q

Electrochemical series

A

List of elements in order of their standard electrode potentials

115
Q

Organic chemistry

A

Organic chemistry is the study of compounds of carbon

116
Q

Hydrocarbon

A

Compound that contains hydrogen and carbon only

117
Q

Fossil fuels

A

Fuels that were formed from the remains of plants and animals that lived millions of years ago

118
Q

Homologous series

A
  • a series of compounds of similar chemical properties
  • showing gradations in physical properties
  • having the same general formula for it’s members
  • each member has a similar method of preparation
  • each member differs from the previous member by a CH2 unit
119
Q

Structural isomer

A

Compounds with the same molecular formula but different structural formulas

120
Q

Unsaturated compound

A

One that contains one or more double or triple bonds between atoms in the molecule

121
Q

Aliphatic compound

A

An organic compound that consists of open chains of carbon atoms and closed chain compounds (rings) that resemble them in chemical properties

122
Q

Aromatic compound

A

Compounds that contain a benzene ring structure in their molecules

123
Q

Auto-ignition

A

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

124
Q

Octane number

A

A measure of the tendency of a fuel to resist knocking

125
Q

Catalytic cracking

A

The breaking down of long chain hydrocarbon molecules, by the action of heat and catalysts, into short chain molecules for which there is great demand

126
Q

Heat of reaction

A

The heat change when the number of moles of reactants indicated in the balanced equation for the reaction react completely

127
Q

Heat of combustion

A

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

128
Q

Bond energy

A

The average energy required to break one mole of a particular covalent bond and to separate the neutral atoms completely from each other

129
Q

Kilogram calorific value

A

The heat energy produced when 1kg of the fuel is completely burned in oxygen

130
Q

Heat of neutralisation

A

The heat change when one mole of H+ ions from an acid react with one mole of OH- ions from a base

131
Q

Heat of formation

A

The heat change that takes place when one mole of a compound in its standard state is formed from its elements in their standard states

132
Q

Hess’s law

A

If a chemical reaction takes place in a number of stages, the sum of the heat changes in the separate steps is equal to the heat change if the reaction is carried out in one stage

133
Q

Law of conservation of energy

A

Energy cannot be created nor destroyed but can only be converted from one form of energy into another

134
Q

Chloroalkane

A

A compound in which one or more of the hydrogen atoms in the alkane molecule have been replaced by chlorine atoms

135
Q

Functional group

A

A functional group is an atom or group of atoms which are responsible for the characteristic properties of an organic compounds or a series of organic compounds

136
Q

Primary alcohol

A

A primary alcohol is one where the carbon atom joined to the OH group is attached to only one other carbon atom

137
Q

Secondary alcohol

A

A secondary alcohol is one where the carbon atom joined to the -OH group is attached to two other carbon atoms

138
Q

Tertiary alcohol

A

A tertiary alcohol is one where the carbon atom joined to the OH group is attached to three other carbon atoms

139
Q

Condensation reaction

A

A chemical reaction in which two molecules combine to form a larger molecule with the loss of a smaller molecule such as water

140
Q

Steam distillation

A

A separation process used to isolate compounds at temperatures below their decomposition temperatures. It is carried out by bubbling steam through the material and distilling off the immiscible liquids

141
Q

Emulsion

A

A dispersion of small droplets of one liquid in another liquid in which it is not soluble

142
Q

Liquid-liquid extraction

A

A technique in which two immiscible liquids (e.g. oil of cloves and water) are separated using a solvent (e.g. cyclohexane) in which one of the components of the mixture (clove oil) has a higher solubility than the other (water). The organic component is removed from the emulsion by dissolving the organic component in an organic solvent.

143
Q

Substitution reaction

A

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

144
Q

Mechanism

A

The detailed step by step description of how the overall reaction occurs

145
Q

Chain reaction

A

A reaction that continues on and on because a product from one step of the reaction is a reactant for another step of the reaction

146
Q

Addition reaction

A

One in which two or more molecules react together to form a single molecule

147
Q

Polymer

A

Long chain molecules made by joining together many small molecules (monomers)

148
Q

The repeating unit of a polymer

A

Part of the polymer that repeats and completes the polymer chain (except for the end groups)

149
Q

Elimination reaction

A

One in which a small molecule is removed from a larger molecule to leave a double bond in the larger molecule

150
Q

Organic synthesis

A

The process of making organic compounds from simpler starting materials

151
Q

Recrystallisation

A

A process of repeated crystallisation in order to purify a solid or to obtain more satisfactory crystals of a solid that is already pure

152
Q

Chromatography

A

A separation technique in which a mobile phase carrying a mixture moves in contact with a selectively adsorbent stationary phase

153
Q

Principle of chromatography

A

The principle on which all chromatographic separation techniques are based is that separation of a mixture of components occurs as a result of selective adsorbance of the components of the mixture on a stationary phase while carried by a mobile phase

154
Q

Principle of gas chromatography

A

The principle of gas chromatography is that a gaseous mobile phase is in contact with a stationary phase (non volatile liquid) and separation of the mixture occurs as a result of selective adsorbance of the components of the mixture on the stationary phase

155
Q

Principle of HPLC

A

The principle of high performance liquid chromatography is that a liquid mobile phase is in contact with a stationary phase (fine particles of a solid) and separation of the mixture occurs as a result of selective adsorbance of the components of the mixture on the stationary phase

156
Q

Principle of IR spectrometry

A

The principle of Infra-red spectrometry is that organic compounds absorb infra-red radiation of certain frequencies. The combinations of frequencies that are absorbed depend on the bonding within the molecule and are unique to a particular molecule

157
Q

Principle of UV absorption spectrometry

A

The principle of ultraviolet absorption spectrometry is that absorbance is directly proportional to the concentration of a substance

158
Q

Properties of cathode rays

A
  • travel in straight lines from cathode to anode
  • can be deflected In electric and magnetic fields
  • have sufficient energy to move a small object such as a paddle wheel

Chemistry (18 decks)

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