why do we use parts per million(ppm)
it can describe very small concentrations of a gas in the atmosphere, if we used % concentration the value would be too low
so what do we mean by co2 having a concentration of 399ppm
there are 399 co2 molecules per a million molecules of air
how do you convert ppm into % concentration
divide by 10000
how do you convert % concentration into ppm
times by 10000
define electromagnetic radiation
energy transmitted as waves with different frequencies and wavelengths
list the types of EM radiation in order of increasing energy and frequency but decreasing wavelength
radio waves, microwaves, infrared radiation, visible light, ultra violet, x-rays and gamma rays
write a nuemonic for this
Rude Monkeys In Velvet Use X-ray Glasses
what are the four types of energy
-vibrational
-rotational
-translational(dont need to know detail)
-electron energy
the types of energy have ________ energy levels
quantised
what do the gaps between vibrational energy levels correspond to
different infrared radiation wavelengths
infrared radiation is detected as _____
heat
how does infrared radiation make skin feel warmer
it makes bonds in the molecules in our skin vibrate more, causing them to have more kinetic energy
why is infrared of a high energy needed to vibrate a C-F bond in comparison to a C-Br bond
C-F is a stronger bond because it has a higher bond enthalpy
what do the gaps between rotational energy levels correspond to
microwave wavelengths
why do changes in rotational energy correspond to microwave wavelengths which are lower energy than IR
making molecules rotate requires less energy than making their bonds vibrate
what do the gaps between electron energy levels correspond to
UV or visible light wavelengths
what three things could happen when a chlorine molecule absorbs EM radiation
-electrons may be excited to a higher energy level
-photodissociation
-ionisation
explain how electrons could be excited to a higher energy level
if the wavelength of visible light absorbed corresponds to a gap between the quantised electron levels, the electron will move from the ground state to an excited state, any unabsorbed light appears green
explain photodissociation
if high energy radiation is absorbed, Cl2 absorbs so much energy that bonding electrons can no longer keep atoms together, causing photodissociation and forming radicals
explain ionisation
if very high energy radiation is absorbed, the molecule may acquire so much energy that an electron is able to leave it
Cl2 -> Cl2+ and e-
why does the sun give out EM radiation
due to nuclear fusion reactions occurring at its core
what are the three main types of EM radiation that the sun emits
-infrared radiation
-visible light
-UV radiation
