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Chemistry IG > Definitions and formulas > Flashcards

Definitions and formulas Flashcards

1
Q

Melting point definition

A

Temperature when a substance begins to change from solid to liquid

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2
Q

Boiling point definition

A

Temperature when a substance begins to change from liquid to gas

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3
Q

Pressure definition

A

The force exerted by gas molecules colliding with surfaces of objects or other particles

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4
Q

Temperature definition

A

The average kinetic energy of the particles in a substance

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5
Q

Diffusion definition

A

Diffusion is the net movement of particles from an area of high concentration to an area of low concentration until they’ve reached equilibrium.

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6
Q

Concentration definition

A

Concentration is a measure of how much of a substance there is in a single area, in other words, the amount of substance per unit volume.

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7
Q

Element definition

A

Pure substances made up of only one type of atom

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8
Q

Compound definition

A

Pure substances that are formed when two or more elements chemically combine

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9
Q

Mixture definition

A

A combination of two or more substances (elements and/or compounds) that arenotchemically combined

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10
Q

Molecule definition

A

Two elements bonded together

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11
Q

Proton number/atomic number definition

A

the number of protons in the nucleus of an atom

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12
Q

Mass number/nucleon number definition

A

the total number of protons and neutrons in the nucleus of an atom

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13
Q

Isotope definition

A

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

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14
Q

Calculating atomic mass using isotopes formula

A

Atomic mass= (fractional abundance of isotope 1 x mass number of isotope 1) + (fractional abundance of isotope 2 x mass number of isotope 2)

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15
Q

Ionic bond definition

A

An ionic bond is a strong electrostatic attraction between oppositely charged ions

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16
Q

Ion definition

A

An ion is an electrically chargedatom or group of atoms formed by the lossor gain ofelectrons

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17
Q

Covalent bond definition

A

A covalent bond is formed when a pair of electrons is shared between two atoms leading to noble gas electronic configurations

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18
Q

Simple molecular substance meaning

A

A simple molecular substance is a covalent substance that is made up of a small number of non-metal atoms held together with a small number of covalent bonds

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19
Q

Giant covalent structure meaning

A

A giant covalent structure is networks made up of a large number of non-metal atoms, held together with a large number of strong covalent bonds

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20
Q

Allotrope meaning

A

An allotrope is two or more physical forms in which an element can exist. E.g. diamond and graphite are both made of carbon

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21
Q

Metallic bonding definition

A

the electrostatic
attraction between the positive ions in a giant metallic lattice and a ‘sea’ of delocalised electrons

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22
Q

Molecular formula definition

A

The number and type of different atoms in one molecule

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23
Q

Empirical formula definition

A

The simplest whole number ratio of the different atoms or ions in a compound

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24
Q

Relative atomic mass (Ar) definition

A

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

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25
Relative molecular mass (Mr) definition
The sum of the relative atomic masses. Relative formula mass is used for ionic compounds
26
Mole definition
A mole (unit: mol) is the unit of amount of substance and one mole contains 6.02 × 10^23 particles, e.g. atoms, ions, molecules; this number is the Avogadro constant
27
Avogadro's constant
Number of atoms in a mole (6.02x10^23)
28
Conversion cm^3 to dm^3
1000cm^3 = 1dm^3
29
Conversion between mol/dm^3 and g/dm^3
To convert between mol/dm^3 and g/dm^3 multiply by molar mass in grams
30
Electrolysis definition
decomposition of an ionic compound, when molten or in aqueous solution, by the passage of an electric current
31
Percentage yield definition and formula
Percentage yield is the ratio of actual yield obtained compared to the expected or theoretical yield Actual yield/theoretical yield
32
Percentage composition by mass formula
total mass of element in compound/relative formula mass of compound
33
Percentage purity formula
Mass of pure substance/total mass of substance
34
Exothermic reaction definition
an exothermic reaction transfers thermal energy to the surroundings leading to an increase in the temperature of the surroundings
35
Endothermic reaction definition
an endothermic reaction takes in thermal energy from the surroundings leading to a decrease in the temperature of the surroundings
36
What are the axes for reaction pathway diagrams?
x-axis: progress of reaction y-axis: energy
37
What is enthalpy change?
the transfer of thermal energy during a reaction is called the enthalpy change, ∆H, of the reaction
38
Unit of enthalpy
kJ/mol
39
Activation energy definition (Ea)
The minimum energy that colliding particles must have to react
40
What type of process is bond breaking and bond making?
- Bond breaking is always an endothermic process as energy needs to be taken in from the surroundings to break the chemical bonds - Bond making is always an exothermic process as energy is transferred to the surroundings as the new bond is formed
41
Enthalpy calculation formula
(ΔH)  = Energy taken in (bonds broken, reactants) - Energy given out (bonds made, products)
42
Catalyst definition
Substance that increases the rate of a reaction and is unchanged at the end of a reaction. It decreases the activation energy of a reaction
43
Hydrated definition
(substance) chemically combined with water
44
Thymolphthalein colour in base and acid
Base: blue Acid: Colourless
45
Water of crystallisation definition
water molecules present in hydrated crystals
46
Redox reaction definition
reactions where oxidation and reduction take place together simultaneously.
47
What is an oxidising agent?
An oxidising agent is a substance that oxidises another substance and is itself reduced
48
What is a reducing agent?
A reducing agent is a substance that reduces another substance and is itself oxidised
49
ANY ELEMENT OXIDATION NUMBER IS 0
50
Strong acid definition
an acid that is completely dissociated in aqueous solution
51
Weak acid definition
an acid that is partially dissociated in aqueous solution (use reversible reaction sign)
52
Amphoteric oxide definition
oxides that react with acids and with bases to produce a salt and water (Al2O3 and ZnO)
53
Solubility rules for salts
(a) sodium, potassium and ammonium salts are soluble (b) nitrates are soluble (c) chlorides are soluble, except lead and silver (d) sulfates are soluble, except barium, calcium and lead (e) carbonates are insoluble, except sodium, potassium and ammonium f) hydroxides are insoluble, except sodium, potassium, ammonium and calcium (partially)
54
Anhydrous definition
substance containing no water
55
Periodic table definition
an arrangement of elements in periods and groups and in order of increasing proton number/ atomic number
56
Trends down group 1
relatively soft metals (a) decreasing melting point (b) increasing density (c) increasing reactivity - They react readily with oxygen and water vapour in air so they are stored under oil to stop them from reacting - Group I metals will react similarly with water, reacting vigorously to produce an alkaline metal hydroxide solution and hydrogen gas
57
Trends down group VII
diatomic non-metals (a) increasing density (b) decreasing reactivity
58
Appearance of halogens at rtp
(a) chlorine, a pale yellow-green gas (b) bromine, a red-brown liquid (c) iodine, a grey-black solid
59
Transition metals characteristics
(a) have high densities (b) have high melting points (c) form coloured compounds (d) often act as catalysts as elements and in compounds having ions with variable oxidation numbers, including iron(II) and iron(III)
60
Alloy definition
alloy is a mixture of a metal with other elements
61
Sacrifical protection definition
a method of corrosion prevention where a more reactive metal is used to protect a less reactive one.
62
Galvanising definition
a process where the iron to be protected is coated with a layer of zinc. This can be done by electroplating or dipping it into molten zinc
63
Functional group definition
an atom or group of atoms that determine the chemical properties of a homologous series
64
Structural formula definition
a structural formula is an unambiguous description of the way the atoms in a molecule are arranged
65
Structural isomer definition
structural isomers as compounds with the same molecular formula, but different structural formulae
66
Homologous series definition
A family of similar compounds with similar chemical properties due to the presence of the same functional group
67
Saturated compound definition
a saturated compound has molecules in which all carbon–carbon bonds are single bonds
68
Unsaturated compound definition
an unsaturated compound has molecules in which one or more carbon–carbon bonds are not single bonds
69
General characteristics of homologous series
(a) having the same functional group (b) having the same general formula (c) differing from one member to the next by a –CH2– unit (d) displaying a trend in physical properties (e) sharing similar chemical properties
70
How to extract metals high in reactivity series?
Electrolysis
71
How to extract metals middle in reactivity series?
These metals are typically extracted by heating with reducing agent such as carbon or carbon monoxide
72
How to extract metals low in reactivity series
Metals lower in the reactivity series are found in nature in their pure form or in less reactive compounds (copper may have to be extracted from its ore by heating with carbon or hydrogen). Called native ores.
73
Hydrocarbon definition
compounds containing only hydrogen and carbon atoms
74
Petroleum definition
mixture of hydrocarbons
75
Uses of the fractions
Refinery gas - gas used in heating and cooking Gasoline/petrol fraction - fuel used in cars Naphtha fraction - a chemical feedstock (raw materials used in the mass production of chemical products) Kerosene/paraffin fraction - jet fuel Diesel oil/ gas oil fraction - fuel used in diesel engines Fuel oil fraction - fuel used in ships and home heating systems Lubricating oil fraction - lubricants, waxes and polishes Bitumen fraction - making roads
76
Substitution reaction definition
one atom or group of atoms is replaced by another atom or group of atoms
77
What is photochemical reaction
- Alkanes undergo a substitution reaction with chlorine in the presence of ultraviolet light (normally sunlight) - The ultraviolet light provides the activation energy (Ea)
78
Addition reaction definition
In an addition reaction, only one product is formed
79
How to produce ethanol- fermentation of glucose
fermentation of aqueous glucose at 25–35°C in the presence of yeast and in the absence of oxygen
80
How to produce ethanol- steam to ethene
catalytic addition of steam to ethene at 300°C and 6000kPa /60 atm in the presence of an acid catalyst
81
Advantages of fermentation
Simple equipment Uses renewable resources Low temp and pressure (lower cost) Less energy needed
82
Disadvantages of fermentation
Slow reaction Batch process (takes lots of stop and start) Produces a dilute solution that needs further processing Carbon dioxide produced which is greenhouse gas
83
Advantages of addition of steam to ethene
Fast reaction Continuous process Creates pure ethanol No greenhouse gases produced but pollutants are formed from the burning of fossil fuels to maintain high temperatures
84
Disadvantages of addition of steam to ethene
High temperature and pressure (cost increase) Non-renewable raw materials (petroleum) Lots of energy needed (more workers) Complex equipment
85
Polymer definition
large molecules built up from many smaller molecules called monomers
86
Addition polymerisation definition
Formed from many unsaturated monomers bonding together to form a long chain polymer with no byproducts
87
Condensation polymerisation definition
Condensation polymers are formed when two different monomers with two functional groups are linked together with the removal of a small molecule, usually water
88
Solvent definition
solvent as a substance that dissolves a solute
89
Solute definition
substance that is dissolved in a solvent
90
Solution definition
mixture of one or more solutes dissolved in a solvent
91
Saturated solution definition
a solution containing the maximum concentration of a solute dissolved in the solvent at a specified temperature
92
Filtrate definition
A liquid or solution that has passed through a filter
93
Residue definition
Substance that remains after evaporation, filtration, distillation or any other similar process
94
Chromatography definition
Chromatography is a technique used to separate mixtures of soluble solid materials so they can be identified
95
Paper chromatography
Paper chromatography is used to separate mixtures of soluble coloured substances, using a suitable solvent
96
Rf formula
Rf = distance travelled by substance/distance travelled by solvent

Chemistry IG (14 decks)

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