The Ozone Story
28 May 2024 14:47
OZ1 Gas concentration conversion
Gas Source from human activity
Gas concentrations are often calculated in parts per million (ppm) or percentage (%).
Carbon dioxide, CO2 Combustion of hydrocarbon fuels, deforestation
These can be converted for better comparison:
Methane, CH4 Cattle farming, landfill sites, rice paddy field, natural gas leaks
1% = 10,000 ppm x 10,000 Nitrous oxide, N2O Fertilised soils, changes in land use
1 ppm = 0.0001% ÷ 10,000
Carbon monoxide, CO Incomplete combustion of hydrocarbons
Nitrogen oxides, NOx Internal combustion engines
OZ2 Interactions of radiation with matter
Wave theory and particle theory of light: Speed of light, c = wavelength, λ x frequency, v
Light can be characterised in two theories, wave theory and particle (or photon) theory. In general, they Speed of light = 3.00 x108
use c = λv and are linked by E = hv which are both explained below
Energy, E = Planck constant, h x frequency, v
Planck constant = 6.63 x10-34
Radiation interacting with matter:
Electromagnetic radiation can cause different changes to chemicals based on the chemical and the amount Absorbing high energy ultraviolet radiation:
of energy involved. It is associated with several different behaviours including: When a molecule absorbs high energy UV, three things can happen
• Translation (molecule moving as a whole) with varying amounts of energy absorbed.
• Rotation (of whole molecule)
• Vibration of bonds 1.) With smaller amounts of high energy UV absorbed, electrons get
• Electron energy excited to higher energy levels, there is a release of energy as the
atom returns to its original state afterwards
Electron energy is quantised, it has fixed levels, and so does all the other types of energy behavioural
change. These changes are determined by the spacing between energy levels. 2.) Higher amounts of high energy UV may cause bonds to absorb so
much energy that they can no longer hold the atom together. This is
The spacing between vibrational energy levels corresponds to the infrared part of the spectrum, which is called photodissociation and radicals, very reactive molecules with
sensed as heat as the radiation makes the bonds vibrate more on your skin. at least one unpaired electron.
Making molecules vibrate needs less energy than making the bonds vibrate, changes in rotational energy 3.) With very high amounts of high energy UV the molecules may get
corresponds to a lower energy and frequency, the microwave region. so much energy that an electron is able to leave it and it is ionised.
Making electronic changes requires the highest energy, exciting electrons to higher electronic energy levels
requires energies from the visible and infrared parts of the spectrum
In order of smallest to biggest energy change required it is,
Rotational - microwave radiation
Vibrational - infrared radiation
Electronic - visible and ultraviolet radiation
OZ3 Radical reactions
Bonds breaking is sometimes called bond fission and can happen two ways, heterolytic fission or homolytic fission.
Heterolytic fission:
Heterolytic fission is when both of the electrons go to one of the atoms in the bond break and this atom becomes negatively charged due to the extra electrons, the other atom is left as
a positive ion. This type of fission happens usually when the bond is already polar.
Homolytic fission:
Homolytic fission is when one of the electrons from the bond break go to each of the atoms, leaving unpaired electrons on both which is signalled with a radical dot. These unpaired
electrons have a strong tendency to react with other substances and radicals are usually formed when the bond is non-polar but can happen in polar bonds too.
Reactive radicals:
Radicals are very reactive as they have unfilled outer shells. Curly arrows show the movement of an electron, double headed curly arrows show the movement of a pair of electron and
single headed arrows show the movement of a single electron. There are three stages in a radical reaction
Initiation:
Initiation is when radicals are formed by dissociation, they are very reactive and will soon react with something else to initiate a radical reaction
e.g. Cl2 + hv --> Cl• + Cl•
Propagation:
The radicals made in the initiation stage then react with other molecules to produce new radicals which keep the reaction going, the propagate the reaction
e.g. Cl• + H2 --> HCl + H•
H• + Cl2 --> HCl + Cl•
Termination:
Occasionally radicals will collide together and terminate the reaction as it removes the radicals
e.g. H• + H• --> H2
Cl• + Cl• --> Cl2
H• + Cl• --> HCl
Methane and chlorine:
Alkanes are generally unreactive, but will react with halogens in the Prescence of light in another radical chain reaction with the same three stages
Initiation - chlorine radicals are formed from chlorine molecules
Cl2 + hv --> Cl• + Cl•
Propagation - chlorine radicals react with methane molecules, and the resulting methyl radicals react with chlorine again
Cl• + CH4 --> HCl + CH3•
CH3• + Cl2 --> CH3Cl + Cl•
Termination - free radicals react to form molecules, often hydrogen chlorine, chloromethane or ethane.
Cl• + Cl• --> Cl2
CH3• + Cl• --> CH3Cl
CH3• + CH3• --> C2H6
OZ4 Rates of reaction
Rate of reaction = change in ___ / time taken
Measuring volumes of gases evolved:
Volumes of gases produced in a reaction can be used to find out the reaction rate, it can be used for a range of experiments where gas is made and must use this apparatus
Chemistry Page 1
28 May 2024 14:47
OZ1 Gas concentration conversion
Gas Source from human activity
Gas concentrations are often calculated in parts per million (ppm) or percentage (%).
Carbon dioxide, CO2 Combustion of hydrocarbon fuels, deforestation
These can be converted for better comparison:
Methane, CH4 Cattle farming, landfill sites, rice paddy field, natural gas leaks
1% = 10,000 ppm x 10,000 Nitrous oxide, N2O Fertilised soils, changes in land use
1 ppm = 0.0001% ÷ 10,000
Carbon monoxide, CO Incomplete combustion of hydrocarbons
Nitrogen oxides, NOx Internal combustion engines
OZ2 Interactions of radiation with matter
Wave theory and particle theory of light: Speed of light, c = wavelength, λ x frequency, v
Light can be characterised in two theories, wave theory and particle (or photon) theory. In general, they Speed of light = 3.00 x108
use c = λv and are linked by E = hv which are both explained below
Energy, E = Planck constant, h x frequency, v
Planck constant = 6.63 x10-34
Radiation interacting with matter:
Electromagnetic radiation can cause different changes to chemicals based on the chemical and the amount Absorbing high energy ultraviolet radiation:
of energy involved. It is associated with several different behaviours including: When a molecule absorbs high energy UV, three things can happen
• Translation (molecule moving as a whole) with varying amounts of energy absorbed.
• Rotation (of whole molecule)
• Vibration of bonds 1.) With smaller amounts of high energy UV absorbed, electrons get
• Electron energy excited to higher energy levels, there is a release of energy as the
atom returns to its original state afterwards
Electron energy is quantised, it has fixed levels, and so does all the other types of energy behavioural
change. These changes are determined by the spacing between energy levels. 2.) Higher amounts of high energy UV may cause bonds to absorb so
much energy that they can no longer hold the atom together. This is
The spacing between vibrational energy levels corresponds to the infrared part of the spectrum, which is called photodissociation and radicals, very reactive molecules with
sensed as heat as the radiation makes the bonds vibrate more on your skin. at least one unpaired electron.
Making molecules vibrate needs less energy than making the bonds vibrate, changes in rotational energy 3.) With very high amounts of high energy UV the molecules may get
corresponds to a lower energy and frequency, the microwave region. so much energy that an electron is able to leave it and it is ionised.
Making electronic changes requires the highest energy, exciting electrons to higher electronic energy levels
requires energies from the visible and infrared parts of the spectrum
In order of smallest to biggest energy change required it is,
Rotational - microwave radiation
Vibrational - infrared radiation
Electronic - visible and ultraviolet radiation
OZ3 Radical reactions
Bonds breaking is sometimes called bond fission and can happen two ways, heterolytic fission or homolytic fission.
Heterolytic fission:
Heterolytic fission is when both of the electrons go to one of the atoms in the bond break and this atom becomes negatively charged due to the extra electrons, the other atom is left as
a positive ion. This type of fission happens usually when the bond is already polar.
Homolytic fission:
Homolytic fission is when one of the electrons from the bond break go to each of the atoms, leaving unpaired electrons on both which is signalled with a radical dot. These unpaired
electrons have a strong tendency to react with other substances and radicals are usually formed when the bond is non-polar but can happen in polar bonds too.
Reactive radicals:
Radicals are very reactive as they have unfilled outer shells. Curly arrows show the movement of an electron, double headed curly arrows show the movement of a pair of electron and
single headed arrows show the movement of a single electron. There are three stages in a radical reaction
Initiation:
Initiation is when radicals are formed by dissociation, they are very reactive and will soon react with something else to initiate a radical reaction
e.g. Cl2 + hv --> Cl• + Cl•
Propagation:
The radicals made in the initiation stage then react with other molecules to produce new radicals which keep the reaction going, the propagate the reaction
e.g. Cl• + H2 --> HCl + H•
H• + Cl2 --> HCl + Cl•
Termination:
Occasionally radicals will collide together and terminate the reaction as it removes the radicals
e.g. H• + H• --> H2
Cl• + Cl• --> Cl2
H• + Cl• --> HCl
Methane and chlorine:
Alkanes are generally unreactive, but will react with halogens in the Prescence of light in another radical chain reaction with the same three stages
Initiation - chlorine radicals are formed from chlorine molecules
Cl2 + hv --> Cl• + Cl•
Propagation - chlorine radicals react with methane molecules, and the resulting methyl radicals react with chlorine again
Cl• + CH4 --> HCl + CH3•
CH3• + Cl2 --> CH3Cl + Cl•
Termination - free radicals react to form molecules, often hydrogen chlorine, chloromethane or ethane.
Cl• + Cl• --> Cl2
CH3• + Cl• --> CH3Cl
CH3• + CH3• --> C2H6
OZ4 Rates of reaction
Rate of reaction = change in ___ / time taken
Measuring volumes of gases evolved:
Volumes of gases produced in a reaction can be used to find out the reaction rate, it can be used for a range of experiments where gas is made and must use this apparatus
Chemistry Page 1
