Leaving Cert Chemistry Term Flashcards
1
Q
Dalton’s Atomic Theory
A
- All matter is made up of very small particles called atoms.
- All atoms are indivisible. They cannot be broken down into simpler particles.
2
Q
Cathode rays
A
Streams of negatively charged particles called electrons. They travel in a straight lines from the cathode to the anode, are deflected by electric and magnetic fields, and have sufficient energy to move a small object such as a paddle wheel.
3
Q
Element
A
A substance that cannot be split into simpler substances by chemical means
4
Q
Dobereiner’s Triad
A
A group of 3 elements with similar chemical properties in which the atomic weight (relative atomic mass) of the middle element is approximately equal to the average of the other two.
5
Q
Newlands Octaves
A
Arrangement of elements in which the first and eighth element, confusing from a particular element have similar properties
6
Q
Mendeleev’s Periodic Law
A
When elements are arranged in order of increasing atomic weight (relative atomic mass), the properties of the element recur periodically
7
Q
Atomic number
A
The number of protons in the nucleus of that atom
8
Q
Modern Periodic TABLE
A
An arrangement of elements in order of increasing atomic number
9
Q
Modern Periodic LAW
A
When elements are arranged in order of increasing atomic number, the properties of the elements recur periodically, .ie the properties displayed by an element are repeated at regular intervals in other elements
10
Q
Mass number
A
The sum of the number of protons and neutrons in the nucleus of an atom of that element
11
Q
Isotopes
A
Atoms of the same element which have different mass numbers due to the different number of neutrons in the nucleus
12
Q
Relative atomic mass
A
The average of the mass numbers of the isotopes of the elements as they occur naturally.
Taking their abundances into account.
Expressed on a scale in which the atoms of the carbon 12 isotope have a mass of exactly 12 units
13
Q
Compound
A
A substance that is made up of two or more different elements combined together chemically
14
Q
Octet Rule
A
When bonding occurs atoms tend to reach an electron arrangement with eight electrons in the outermost energy level
15
Q
Ion
A
A charged atom or group of atoms
16
Q
Ionic bond
A
The force of attraction between oppositely charged ions in a compound. Ionic bonds are always formed by the complete transfer of electrons from one atom to another.
17
Q
Molecule
A
A group of atoms joined together the smallest particle of an element or compound that can exist independently
18
Q
Valency
A
The number of bonds the atom of an element forms when it reacts
19
Q
Electronegativity
A
The relative attraction that an atom in a molecule has for the shared pair of electrons in a covalent bond
20
Q
Polar covalent bond
A
A bond in which there is unequal sharing of the pair of electrons. This causes one end of the bond to be slightly positive and the other end slightly negative
21
Q
Intramolecular forces
A
Bonding takes place within a molecule, i.e it holds the atoms together. Covalent bonding and polar covalent bonding are examples of intramolecular bonding
22
Q
Intermolecular forces
A
The forces of attraction that exist between molecules. Van der Waals forces, dipole-dipole forces and hydrogen bonding are examples of intermolecular forces
23
Q
Van der Waals forces
A
Weak attractive forces between molecules resulting from the formation of temporary dipoles. They are the only forces of attraction between non-polar molecules
24
Q
Mole
A
Th amount of that substance that contains 6 x 10*23 particles of that substance
25
Dipole-dipole forces
Forces of attraction between the negative pole of one polar molecule and the positive pole of another polar molecule
26
Hydrogen bonds
Type of dipole-dipole attractions between molecules in which hydrogen atoms are bonded to nitrogen, oxygen or fluorine. The hydrogen atom carries a partial positive charge and is attracted to thr electronegative atom in another molecule. Thus, the hydrogen bond acts as a bridge between two electronegative atoms in separate molecules
27
Law of Conservation Mass
The total mass of the products of a chemical reaction is the same as the total mass of the reactants
28
Law of Conservation of Matter
In any chemical reaction, matter is neither created nor destroyed but merely changed from one form into another
29
Relative molecular mass
The average mass of one molecule of that compound compared with one twelfth of the mass of one atom of the carbon-12 isotope.
30
Gas
A substance that has no well-defined boundaries but diffuses rapidly to fill any container in which its placed
31
Boyle's Law
At constant temperature, the volume of a fixed mass of gas is inversely proportional to its pressure
pV= K
32
Charles' Law
At constant pressure, the volume of a fixed mass of gas, is directly proportional to its temperature measured on the Kelvin Scale
V/T = k
33
Gay-Lussac's Law of Combining Volumes
In a reaction between gases, the volumes 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.
34
Avogadro's Law
Equal volumes of gases contain equal numbers of molecules under the same conditions of temperature and pressure
35
Ideal gas
A gas that perfectly obeys all the assumptions of the kinetic theory of gases under all conditions of temperature and pressure.
36
Real gas
Differ from ideal gases because.
i) Forces pf attraction and repulsion do exist between the molecules and
ii) the volume of the molecule is not negligible
37
Arrehnius' definition of an acid
A substance that dissociates in water to produce H+ ions
38
Arrhenius' definition of a strong acid
A substance that almost completely dissociates in water to produce hydrogen (H+) ion
39
Arrhenius' definition of a weak acid
A substance that only slightly dissociates in water to give hydrogen ions
40
Arrhenius' definition of a base
A substance that dissociates in water to produce hydroxide ions
41
Arrhenius' definition of a strong base
A substance that almost completely dissociates in water to give hydroxide ions
42
Arrhenius' definition of a weak base
A substance that only slightly dissociates in water to produce hydroxide ions
43
Brønsted-Lowry's definition of a strong acid
A good proton donor
44
Brønsted-Lowry's definition of a weak acid
A poor proton donor
45
Brønste Lowry's definition of a strong base
A good proton acceptor
46
Brønsted-Lowry's definition of a weak base
A poor proton acceptor
47
Conjugate acid base pair
Any pair consisting of an acid and a base that differ by one proton
48
Salt
The substance formed when the hydrogen ion from an acid is replaced by a metal or an ammonium ion
49
Neutralization
The reaction between an acid and a base to form a salt and water
50
Solution
A completely perfect mixture of a solute and a solvent. In a solution the particles of the solute are uniformly distributed throughout the solvent
51
Molarity
The number of moles of solute per litre of solution
52
Standard solution
A solution whose concentration is accurately known
53
Primary standard
A substance that can be obtained in a stable, pure and soluble solid form so that it can be weighed out and dissolved in water to give a solution of accurately known concentration
54
Titration
A laboratory procedure where a measured volume of one solution is added to a known volume of another solution until the reaction is complete
55
Energy level
The fixed energy value that an electron in an atom may have
56
Ground state
The electrons occupy the lowest available energy levels
57
Excited state
The electrons occupy a higher energy levels than those available in the ground state
58
Heisenbergs Uncertainty Principle
It's impossible to measure at the same time both the velocity and the position of an electron
59
Sublevel
A subdivision of a main energy level and consists of one or more orbitals of the same energy
60
Principles of mass spectrometry
Charged particles moving in a magnetic field are deflected to different extents according to their masses and are thus separated according to these masses
61
Electron configuration
Shows the arrangement of electrons in an atom of an element
62
Aufbau Principle
When building up the electron configuration of an atom in its ground state the electrons occupy the lowest available energy levels
63
Hund's Rule of Maximum Multiplicity
When two or more orbitals of equal energy are available the electrons occupy them singly before filling them in pairs
64
Pauli Exclusion Principle
No more than two electrons may occupy an orbital and they must have opposite spin
65
Transition metal
One that forms at least one ion with a partially filled d sublevel
66
Sigma bond
Formed by the head on over lap of two orbitals
67
Pi bonds
Formed by the sideways overlap of porbitals
68
Atomic radius
Half the distance between the nuclei of two atoms of the same element that are joined together by a single covalent bond
69
First ionisation energy
The minimum energy required to remove the most loosely bound electron from a neutral gaseous atom in its ground state
70
Second Ionisation energy
The energy required to remove an electron from an ion with one positive charge in the gaseous state
71
Radioactivity
The spontaneous breaking up of unstable nuclei with the emission of one or more types of radiation
72
Nuclear reaction
A process that alters the composition, structure or energy of an atomic nucleus
73
Half life
The time taken for half of the nuclei in any given sample to decay
74
Radioisotope
Radioactive isotope
75
Radiocarbon dating
A technique used to determine the age of an object containing carbon. It is based on the ratio of carbon-14 to carbon-12 in the object
76
Molecular formula
A formula that shows the number and type of each atom present in a molecule of that compound
77
Empircal formula
The formula showing the simplest whole number ratio of the numbers of different atoms present in the molecule
78
Oxidation
When an element loses electrons
Or
Oxidation number is increased
79
Reduction
When an element gains electrons
Or
Oxidation number decreases
80
Oxidising agent
A substance that brings about oxidation in other substances
81
Reducing agent
A substance that brings about reduction in other substances
82
Oxidation number
The charge that an atom has or appears to have when electrons are distributed according to certain rules
83
Rate of reaction
The change in concentration per unit time of any one reactant or product
84
Instantaneous rate of reaction
The rate of reaction at any one particular time during the reaction
85
Catalyst
A substance that alters the rate of a chemical reaction but is not consumed in the reaction
86
Enzyme
A substance that is produced by a living cell and acts as a biological catalyst
87
Homogeneous catalyst
Catalysis in which both the reactants and the catalyst are in the same phase
88
Heterogeneous catalysis
Catalysis in which the reactants and the catalyst are in different phases
89
Autocatalysis
A catalysis in which one of the products of the reaction acts as a catalyst for the reaction
90
Catalytic converter
A device in rhe exhaust system of a motor vehicle which contains catalysts to convert pollutants in the exhaust gases to less harmful substances
91
Catalyst poison
A substance that makes a catalyst inactive
92
Effective collision
One that results in the formation of products
93
Activation Energy
The minimum energy that colliding particles must have for a reaction to occur
94
Reaction Profile Diagram
A graph that shows the change in energy of a chemical reaction with time as the reaction progresses
95
Reversible reaction
The products react to give back the reactants
96
Chemical equilibrium
A state of dynamic balance in a reversible reaction where the rate of the forward reaction is the same as the rate of the backward reaction
97
Dynamic State
The reactants are continuously forming products and the products are continuously forming reactants
98
Dynamic equilibrium
The rate of the forward reaction is equal to the rate of the backward reaction
99
Le Châteliers Principle
If a stress is applied to a system at equilibrium the system re-adjusts to relieve the stress applied
100
Acid base indicator
As substance that changes colour according to the pH of the solution in which it is placed
101
Range of an indicator
The pH interval over which there is a clear change of colour for that indicator
102
Hard water
Water that will not easily form a lather with soap. Hardness in water is caused by Ca(2+) or Mg(2+) ions dissolved in the water
103
Temporary hardness
Hardness that can be removed by boiling the water
104
Permanent hardness
Hardness which cannot be removed by boiling the water
105
Complexometric titration
A titration involving the formation of a complex between metal ions and a reagent such as edta. In this type of titrations the end point is marked by a sharp decrease in the concentration of free metal ions
106
Flocculation
The coming together of small suspended particles in the water
107
Flocculating agents
A chemical added to water to coagulate suspended particles and thus help sedimentation to take place
108
Biochemical oxygen demand
The amount of dissolved oxygen consumed by biological action when a sample of water is kept at 20*C in the dark for five days
109
Eutrophication
The enrichment of water with nurtrients leading to excessive growth of algae and other plants
110
Primary treatment of sewage
Mechanical process in which large solids are removed by screening and some suspended solids are removed by settlement
111
Secondary treatment of sewage
Biological oxidation process in which the levels of suspended and dissolved organic materials are reduced
112
Tertiary treatment of sewage
A process involving the removal of phosphorus compounds by precipitation and the removal of nitrogen compounds by biological and ion exchange methods
113
Principle of colorimetry
The amount of absorbance of light by a coloured solution is proportional to the concentrarion of the solution
114
Electrolysis
The use of electricity to bring about a chemical reaction in an electrolyte
115
Electrolyte
A compound which when molten or dissolved in water will conduct an electric current
116
Electroplating
A process where electrolysis is used to put a layer of one metal on the surface of another
117
Electrochemical series
A list of elements in order of their standard electrode potentials
118
Organic chemistry
The study of compounds containing carbon
119
Hydrocarbon
A compound that contains carbon and hydrogen ONLY
120
Fossil fuels
Fuels that were formed from the remains of plants and animals that lived millions of years ago
121
Saturated compound
A compound which there are only single bonds between the carbon atoms in the molecule
122
Homologous series
A series of compounds of similar chemical properties
Showing gradations in physical properties
Having a general formula for its members
Each member having a similar method of preparation
Each member differing from the previous member by a CH2 unit
123
Structural isomer
Compounds with the same molecular formula but different structural formulas
124
Unsaturated compounds
One that contains one or more double or triple bonds between the atoms in the molecule
125
Aliphatic compound
An organic compound that consists of open chains of carbon atoms and closed chain compounds that resemble them in chemical properties
126
Aromatic compounds
Compounds that contain a benzene ring structure in their molecule
127
Octane number
A measure of the tendency of the fuel to resist knocking
128
Catalytic cracking
The breaking down of long-chain hydrocarbon molecules by the action of heat and catalysts into short-chain molecules for which there is greater demand
129
Heat of reaction
The heat change when the number of moles of reactants indicated in the balanced equation for the reaction react completely
130
Heat of combustion
A substance is the heat change when one mole of the substance is a completely burned in excess oxygen
131
Kilogram calorific value
The heat energy produced when 1 kg of the fuel is completely burned in oxygen
132
Bond energy
The average energy required to break one mole of a particular covalent bond and to separate the neutral atoms completely from each other
133
Heat of neutralisation
The heat change when one mole of H+ ions from an acid reacts with one mole of OH- ions from a base
134
Heat of formation
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
135
Hess Law
If a chemical reaction takes place in a number of stages the sum of the heat changes in the separate stages is equal to the heat change if the reaction is carried out in one stage
136
Chloroalkane
A compound in which one or more of the hydrogen atoms in an alkane molecule have been replaced by chlorine atoms
137
Functional group
An atom of group of atoms which is responsible for the characteristic properties of an organic compound or a series of organic compounds
138
Primary alcohol
One where the carbon atom joined to the -OH group is attached to only one other carbon atom
139
Secondary alcohol
Where the carbon atom joined to the -OH group is attached to two other carbon atoms
140
Tertiary alcohol
Where the carbon atoms joined to the -OH group is attached to three other carbon atoms
141
Condensation reaction
A chemical reaction in which two molecules combine to form a largee molecule with the loss of a smaller molecule such as water
142
Steam distillation
A separation process used to isolate compounds at temperature below their decomposition temperatures. It is carried out by bubbling steam through the material and distilling off the immiscible liquids
143
Principle of steam distillation
A mixtuee of two immiscible liquids boils at temperature that is below that of the boiling point of each of the individual liquids. The hot mixture of water vapour and oil is passed through a condensor and the distillate that is collected contains a mixture of water and oil
144
Emulsion
A dispersion of small droplets of one liquid in another liquid in which it is not soluble
145
Liquid liquid extraction
A technique in which two immiscible liquids are separated using a solvent in which one of the components of the mixture has a higher solubility than the other
146
Substitution reaction
A chemical reaction in which the atom or group of atoms in a molecule is replaced by another atom or group of atoms
147
Mechanism
The detailed step by step description of how the overall reaction occurs
148
Chain reaction
A reaction that continues on and on because a product from step one of the reaction is a reactant for another step of the reaction
149
Addition reaction
Two or more molecules react together to form a single molecule
150
Polymers
Long chain molecukes made by joining together many small molecules
151
Repeating unit
That part of the polymer whose repetition produces the complete polymer chain except for the end groups
152
Elimination reaction
A small molecule is removed from a larger molecule to leave a double bond in the larger molecule
153
Organic synthesis
The process of making organic compounds from simpler starting materials
154
Recrystallisation
A process of repeated Crystallisation in order to purify a solid or to obtain more satisfactory crystals of a solid that is already pure
155
Chromatography
A separation technique in which a mobile phase carrying a mixture moves in contact with a selectively adsorbent stationary phase
156
Principle of gas chromatography
A gaseous mobile phase is in contact with a stationary phase and separation of the mixture occurs as a result of selective adsorbance of the components of the mixture on the stationary phase
157
Principle of high performance
A liquid in mobile phase is in contact with a sationary phase and separation of the mixture occurs as a result of selective adsorbance of the components of the mixture on the starionary phase
158
Principle of infra red spectrometry
Organic compounds absorb infra red radiation of certain frequencies. The combinations of frequencies that are adsorbed depend on the bonding within the molecule and are unique to the particular molecule
159
Principle of ultraviolet absorption spectrometry
Absorbance is directly proportional to the concentration of a substance
