Sec 2 Express CT1.2009 Answer

Here is the marking scheme for your Common Test (Term 1, 2009)
Please understand that this is only a guideline. I must read your whole answer in context in order to award the correct marks.

Sec 2 Express

Question 1ai)
- Similar pattern for all 3 gases
- Increase slower/steadily before 1900
- Begin accelerating after 1900
- Sharp increase around year 1950/ very steep curve
Any 3 clear descriptions of the trend/pattern observed in the graphs.No mark for only mere description of any graph without stating any trend or pattern.

Question 1aii)
- Increase population (esp. sharp increase around 1950) leads to increase demand for food and land
- More forests are destroyed for food/agricultural and residential purposes
- When more forests are destroyed, CO2 in the atmosphere will increase. Moreover, some forests are destroyed through burning, which will release more CO2.
- Increased wet rice farms and cattle ranches caused by demand from a larger population increases the release of methane
- More fertilisers are used on farms to increase food production. This account for the increase in nitrous oxide in the atmosphere.
5 points @ 1 mark each

Question 1b)
- Carbon Dioxide
- CO2 remains in the atmosphere a lot longer than most of the other gases
- CO2 is released into the atmosphere on a daily basis e.g. burning of fossil fuel
- Industrialisation and number of motor vehicle on the road is still increasing as more countries become develop
- Deforestation removes trees, which should control the amount of CO2
- Deforestation which involves burning of trees will further increase amount of CO2
6 points @ 1 mark each

Question 1c)
- Increasing global temperature leading to the melting of glaciers, ice in north and south pole
- Habitat of polar bears (Arctic circle) is being destroyed as the ice melts
- Without suitable habitat for food and reproduction, the polar bear will face extinction
- Global warming will cause more extreme weather condition (e.g. hotter summers, flooding)
- Farmers are unable to cultivate crop during the expected seasons, and harvest is destroyed by the extreme weather
- This harvest usually provide food for the Cambodians for the rest of the year
- This results in food shortage for the Cambodians in year 2002
2 marks for each phenomenon.
Students are expected to explain all 3 phenomenon. Total = 6m

Question 2ai)
- increasing car ownership will lead to more vehicles on the road
- this leads to an increase in the burning of fossil fuel
- when this happens, vehicles emit large amount of dust and soot, and poisonous gases, such as carbon monoxide and nitrogen oxides into the atmosphere
3 points @ 1 mark each

Question 2aii)
- As Beijing becomes more developed, more power is generated in the power station.
- There will also be more manufacturing plants in the city
- The burning of fossil fuel from these sources will release greater amount of soot, and poisonous gas such as sulphur dioxide into the atmosphere
- In addition, more buildings will be built to accommodate the increasing population and businesses
- The clearing of land, construction of buildings and even transportation of building materials will increase the amount of dust and smoke particles in the atmosphere.
- These contribute to the air pollution in Beijing
Max 1 mark for mere listing of factors without any brief explanation.
1 mark for activity + 1 mark for description/brief explanation; total 2 activities

Question 2aiii)
- When there is severe air pollution, people in Beijing will experience health problems such as asthma and bronchitis
- In severe cases, the toxic gases will attack their lungs and cause lung diseases. In some cases, this will eventually lead to death
- Air pollution will affect the workforce when more people have to take medical leave due to poor health
- Air pollution will also affect visibility and therefore affect transportation
- There will be more accidents on the road, hindering the transportation of goods and people
- Planes at airport might not able to take off and this will also affect the tourism and import/export industries.

6 points @ 1 mark each
Max 3 marks for either economic effects or social effects
Max 1 mark for mere listing of effects


Question 2bi)
- The waste of the infected person can be deposited into the septic tank or at a river.
- If there are cracks in the septic tank, the bacteria will travel/spread underground towards the well. Bacteria from the river will also flow underground towards the well
- When the bacteria enter the well, the well water will become polluted with the bacteria
3 points @ 1 mark each

Question 2bii)
- People who uses/consume the well water and river directly will fall sick
- Children who bathe and play at the river will also contract the illness
- Fishes in the river might become infected with the bacteria
- If these fishes are caught as food supply for the community, people who consume them might also fall ill

4 points @ 1 mark each
Proper explanation expected; e.g. of unacceptable answer: "People fall sick."