Describe how these gases contribute to the greenhouse effect.

(i)     Identify by chemical formula one other greenhouse gas not mentioned above.

(ii)     State the source of this gas.

Many scientists claim that global warming is associated with the increasing concentration of greenhouse gases in the atmosphere. Other than temperature change, state two effects of global warming.

greenhouse gases are transparent to/allow passage of short(er)-wavelength/high(er)-energy radiation/UV light from the Sun / OWTTE;

greenhouse gases absorb long(er)-wavelength/IR radiation from the Earth / OWTTE;

(part of) absorbed radiation is re-radiated back to the Earth / OWTTE;

Do not accept reflected or trapped.

Award [2] for any of the following combinations:

(i)     \({{\text{N}}_{\text{2}}}{\text{O}}\);

(ii)     combustion/burning of biomass / nitrogenous/artificial/synthetic fertilizers / bacterial action;

OR

(i)     \({\text{S}}{{\text{F}}_{\text{6}}}\);

(ii)     electronics industry / electrical switches / production of magnesium / gas-insulated substations;

OR

(i)     \({\text{N}}{{\text{F}}_{\text{3}}}\);

(ii)     electronics industry / manufacture of semi-conductors / LCDs/liquid-crystal displays / thin-film solar cells / solar panels / chemical lasers;

OR

(i)     \({\text{S}}{{\text{F}}_{\text{5}}}{\text{C}}{{\text{F}}_{\text{3}}}\);

(ii)     (by-product from SF\(_6\) in) high-voltage equipment / discharge / by-product of fluorochemical manufacture;

Award [1] for any two of the following:

melting of polar ice-caps/glaciers;

changes in yield and distribution of crops / changes in agriculture/biodiversity / changes in habitats;

droughts / desertification / flooding / decreased water quality due to flooding / lack of fresh drinking water / changes in precipitation;

Allow climate change.

rising sea-levels / thermal expansion of oceans / decreased dissolved oxygen / changes in distribution of pests and disease-carrying organisms / increased spread of diseases by insects/mosquitos moving to new areas / chance of malaria;

Many candidates struggled with this question; they discussed the destruction of ozone instead of the greenhouse effect. Responses indicated poor understanding of the role of UV and IR and the terms trapped and reflected were often used to explain the role of greenhouse gases. Some candidates neglected to properly discuss how the energy (UV) enters the atmosphere through the gases and how the energy (IR) is absorbed from the Earth (not the sun) and re-radiated back to the Earth. Very few candidates scored 3 marks for part (a). Candidates also struggled with identifying other greenhouse gases for part (b). Many listed the gases in the stem that they were directed not to use; many incorrect gases were identified (CO, \({\text{N}}{{\text{O}}_{\text{2}}}\), \({\text{S}}{{\text{O}}_{\text{2}}}\), \({\text{S}}{{\text{O}}_{\text{3}}}\)). Majority of the candidates failed to score the two marks. Candidates demonstrated a good understanding of the effects of global warming, scoring the mark for part (c).

Many candidates struggled with this question; they discussed the destruction of ozone instead of the greenhouse effect. Responses indicated poor understanding of the role of UV and IR and the terms trapped and reflected were often used to explain the role of greenhouse gases. Some candidates neglected to properly discuss how the energy (UV) enters the atmosphere through the gases and how the energy (IR) is absorbed from the Earth (not the sun) and re-radiated back to the Earth. Very few candidates scored 3 marks for part (a). Candidates also struggled with identifying other greenhouse gases for part (b). Many listed the gases in the stem that they were directed not to use; many incorrect gases were identified (CO, \({\text{N}}{{\text{O}}_{\text{2}}}\), \({\text{S}}{{\text{O}}_{\text{2}}}\), \({\text{S}}{{\text{O}}_{\text{3}}}\)). Majority of the candidates failed to score the two marks. Candidates demonstrated a good understanding of the effects of global warming, scoring the mark for part (c).

Many candidates struggled with this question; they discussed the destruction of ozone instead of the greenhouse effect. Responses indicated poor understanding of the role of UV and IR and the terms trapped and reflected were often used to explain the role of greenhouse gases. Some candidates neglected to properly discuss how the energy (UV) enters the atmosphere through the gases and how the energy (IR) is absorbed from the Earth (not the sun) and re-radiated back to the Earth. Very few candidates scored 3 marks for part (a). Candidates also struggled with identifying other greenhouse gases for part (b). Many listed the gases in the stem that they were directed not to use; many incorrect gases were identified (CO, \({\text{N}}{{\text{O}}_{\text{2}}}\), \({\text{S}}{{\text{O}}_{\text{2}}}\), \({\text{S}}{{\text{O}}_{\text{3}}}\)). Majority of the candidates failed to score the two marks. Candidates demonstrated a good understanding of the effects of global warming, scoring the mark for part (c).