Describe how the greenhouse effect causes the atmosphere of the Earth to increase in temperature.

Identify one greenhouse gas other than \({\text{C}}{{\text{O}}_{\text{2}}}\) and \({{\text{H}}_{\text{2}}}{\text{O}}\) and suggest a significant source.

incoming solar radiation is short wavelength/high frequency/higher energy/UV;

(re-)radiated/emitted (by Earth’s surface) as long wavelength/low frequency/low energy/IR radiation;

energy absorbed by (bonds in) greenhouse gases / molecules vibrate when IR radiation absorbed;

energy (re-)radiated/(re-)emitted as IR radiation some of which returns back to Earth;

Do not accept reflected, bounced or trapped.

\({\text{C}}{{\text{H}}_{\text{4}}}\) / methane;

decomposition of organic matter / livestock/ruminant/cows/sheep / manure / swamps/marshes / rice paddies / oil/gas field / anaerobic microbial activity in lakes/ponds / composting;

OR

\({{\text{N}}_{\text{2}}}{\text{O}}\) / nitrogen(I) oxide/dinitrogen monoxide/nitrous oxide;

bacterial decomposition/action / combustion/burning of biomass / artificial/nitrogeneous/synthetic fertilizers;

OR

CFCs / chlorofluorocarbons;

solvents / production of polymers / refrigerants / foaming agents / propellants/aerosols / air conditioning units;

OR

\({\text{S}}{{\text{F}}_{\text{6}}}\) / sulfur hexafluoride;

electronics industry / high voltage/electrical switches / circuit breakers / electrical generators / insulator used in electrical industrial applications/gas-insulated substations / production of magnesium / OWTTE;

Accept any other correct answers such as “nitrogen trifluoride/NF₃ used in electronics industry / manufacture of semi-conductors/computer chips/circuits / (thin-film) solar/photovoltaic cells / solar panels / LCD televisions / chemical lasers” OR “trifluoromethyl sulfur pentafluoride/SF₅CF₃ formed (as by-product from SF₆) in high-voltage equipment / by-product of fluorochemical manufacture”.

M2 can only be scored if M1 correct.

The greenhouse effect has been asked on several occasions in the past and there have been widespread references to the performance of candidates on this question in previous subject reports. Hence it was extremely disappointing and surprising to see such poor answers.

Journalistic type answers were common and vague terminology such as bounced and reflected were often used. In addition answers were sometimes unclear – for example some candidates did not mention incoming solar radiation and just blankly alluded to the involvement of UV rays. In contrast (b) was well answered. The most common mistake involved candidates stating \({\text{N}}{{\text{O}}_{\text{2}}}\) instead of \({{\text{N}}_{\text{2}}}{\text{O}}\), a classic mistake on IB Chemistry papers.

The greenhouse effect has been asked on several occasions in the past and there have been widespread references to the performance of candidates on this question in previous subject reports. Hence it was extremely disappointing and surprising to see such poor answers.

Journalistic type answers were common and vague terminology such as bounced and reflected were often used. In addition answers were sometimes unclear – for example some candidates did not mention incoming solar radiation and just blankly alluded to the involvement of UV rays. In contrast (b) was well answered. The most common mistake involved candidates stating \({\text{N}}{{\text{O}}_{\text{2}}}\) instead of \({{\text{N}}_{\text{2}}}{\text{O}}\), a classic mistake on IB Chemistry papers.