OZ 1, 2, 3 Flashcards
what are the names of the parts of the atmosphere from top to bottom?
-thermosphere
-mesosphere
-stratosphere
-troposphere
how do the sections of atmosphere vary in density and temperature
- the higher up that you go, the less dense it becomes (90% of all molecules are found in the troposphere)
- the higher that you go, the hotter it becomes, because hot gases rise and cold gases fall
what is gas measured in when the concentration is small
parts per million (ppm)
describe and explain the evolution of the atmosphere `
- there was originally very little oxygen, and the first simple plants began producing oxygen by photosynthesis
- when o2 conc reached about 10%, animals began to evolve by respiration
- the oxygen conc remained at 21%
- human activities add more gases to the atmosphere e.g. CFCs and HFCs and increase the conc of others e.g. carbon dioxide
what are the effects of electromagnetic radiation
-breaks bonds in DNA molecules, causes damage to genes and can lead to skin cancer
-causes damage in proteins in the skin, years of exposure causes one to look wrinkly
-irritates blood vessels which causes skin to look red and burn
why can you get sun burnt under water but not when sitting in a green house
the glass of the green house absorbs the ultra violet radiation but water does not absorb all of it
what do sunscreens contain and why
contain many benzene rings or alternating double and single bonds so when uv light is absorbed, electrons in pi bonds jump to higher energy levels
where is most uv light absorbed
upper atmosphere called the stratosphere
what absorbs most uv light
ozone, oxygen gas in the form of O3
where is ozone a pollutant and why
at ground level in the troposphere because it’s involved in reactions that produce photochemical smog
what is the speed of light
3.00 X 10^8 m/s
equation for the speed of light
c = wavelength (m) X frequency (s)
how to calculate the energy of a photon
E (J) = planks constant (Js) X frequency (s)
what is planks constant
6.63 X 10^-34 Js
what are the different kind of electron activities in order of increasing energy
- translation
- rotation
- vibration of the bonds
- electronic energy
these all involve different amounts of energy
define electronic energy being quantised
it has fixed levels
what causes molecules to vibrate
infrared radiation
spacing between vibrational energy levels corresponds to the infrared part of the spectrum.
makes bonds in skin chemicals vibrate more energetically, they gain kinetic energy which is why we sense it as heat
what causes molecules to rotate
- requires less energy than vibrational, therefore corresponds to a lower energy part of the EM spectrum
- the microwave region
what causes changes in electronic energy
- higher than all levels
- exciting electrons to a higher electronic energy level requires energy corresponding to visible and UV parts of the spectrum
what three things can happen when a molecule absorbs radiation
- electrons can be excited to a higher energy level
- if the radiation is higher energy, the bonding electrons can no longer hold the atoms together (photodissociation)
- if the photon is very high energy, the electron can leave the molecule so it is ionised
define radical
molecules or atoms with at least one unpaired electron, and are usually very reactive
what is heterolytic fission
both of the shared electrons go to the same atom, and it then becomes negatively charged
what is homolytic fission
the two shared electrons each go to different atoms, they are each written with a dot beside them
how is ozone formed
when an oxygen atom reacts with a dioxygen molecule
how is ozone formed in the troposphere
by the action of sunlight on the pollutant of nitrogen oxide
hoe is ozone formed in the stratosphere
photodissociation of dioxygen molecules when uv radiation of the right frequency is absorbed
(10.1 - 14) X 10^14
why are radicals really reactive
they’re always trying to grab electrons from other atoms or molecules
name and escribe the stages of a radical chain reaction
initiation - starts with no radical, ends with a radical
propagation - starts with a radical and ends with a different one
termination - starts with a radical, doesn’t end with one
write out radical chain reaction of hydrogen chloride formation
INITIATION
Cl2 + hv —–> Cl* + Cl*
PROPAGATION
Cl* + H2 —-> HCl + H*
H* + Cl2 —-> HCl + Cl*
TERMINATION
H* + H* —-> H2
Cl* + Cl* —-> Cl2
H* + Cl* —-> HCl
what is the radical chain reaction for methane and chlorine
initiation
Cl2 + hv —-> Cl* + Cl*
propagation
Cl* + CH4 —-> HCl + CH3*
CH3 + Cl2 —-> CH4 + Cl*
termination
CH3* + Cl* —-> CH3Cl
Cl* + Cl* —-> Cl2
CH3* + CH3* —-> C2H6
