Suggest why it is only in recent years that specific predictions of the future effects of fossil fuel combustion have been made.

Carbon dioxide has two different bond stretching modes illustrated below.

Predict, with an explanation, whether these stretching modes will absorb infrared radiation.

Outline, giving the appropriate equation(s), how increasing levels of carbon dioxide will affect the pH of the oceans.

Many combustion processes also release particulate matter into the atmosphere. Suggest, giving your reason, how this might affect the temperature of the Earth’s surface.

computers can now carry out more complex calculations
OR
better understanding of the interactions between the various systems involved
OR
clear evidence of global warming
OR
«reliable» global temperature data now available
OR
techniques have been available to monitor carbon dioxide levels

Accept “better/faster computers”.

Accept “better modelling”.

Accept “better/more reliable/consistent data”.

Accept “better measuring techniques”.

Accept other scientifically based (not politically based) reasons.

Accept if specific relevant data is given.

Do not accept “increased combustion of fossil fuels” or “increased concerns about global warming”.

[1 mark]

symmetric stretching will not absorb IR
OR
asymmetric stretching will absorb IR

change in polarity/dipole «moment» required «to absorb IR»

[2 marks]

CO₂(aq) + H₂O(l) \( \rightleftharpoons \) H⁺(aq) + HCO₃^–(aq) «and pH decreases»
OR
CO₂(aq) + H₂O(l) \( \rightleftharpoons \) H₂CO₃(aq) AND H₂CO₃(aq) \( \rightleftharpoons \) H⁺(aq) + HCO₃^–(aq) «and pH decreases»

Accept reversible or non-reversible arrows for all.

[1 mark]

reduce it AND absorbing/reflecting sunlight

Accept “reduce it because of global dimming”.

Accept “reduce it AND blocking sunlight”.

[1 mark]