Fuels, climate and alternativesIB MYP Sciences: Subtopic test

1. 1
   A geography class in Auckland reads a climate report. It says that Earth's average surface temperature is about 15 °C, but without an atmosphere it would be about -18 °C. Some gases in the atmosphere absorb heat radiated from Earth's surface. The carbon dioxide concentration in the atmosphere has risen from about 280 parts per million before 1800 to over 420 parts per million today.

   (a)

   Which of these gases is a greenhouse gas?

   [1 mark]

   • ANitrogen
   • BOxygen
   • CMethane
   • DArgon

   (b)

   What is the main reason for the rise in carbon dioxide concentration since 1800?

   [1 mark]

   • ABurning fossil fuels and cutting down forests
   • BThe Sun giving out stronger sunlight
   • CA hole in the ozone layer letting carbon dioxide in
   • DMore photosynthesis by plants

   (c)

   Explain how greenhouse gases keep Earth's surface warmer than it would be without an atmosphere.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A bus company in São Paulo is considering replacing its diesel buses with buses that run on bioethanol, a biofuel made by fermenting sugar cane, or with hydrogen fuel-cell buses.

   (a)

   Why is bioethanol described as a renewable fuel?

   [1 mark]

   • AIt is made from crude oil
   • BThe crops it is made from can be grown again
   • CIt does not contain any carbon
   • DIt makes no gases when it burns

   (b)

   What is made when hydrogen reacts with oxygen in a fuel cell or by burning?

   [1 mark]

   • ACarbon dioxide
   • BCarbon monoxide
   • CSulfur dioxide
   • DWater

   (c)

   Suggest one advantage and one disadvantage of using hydrogen as a fuel for buses.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   Arjun, a student in Chennai, compares the energy released by three fuels: ethanol (a biofuel), biodiesel and kerosene. For each fuel, he burns exactly 1.0 g in a spirit burner under a metal can containing 200 cm³ of water and measures the rise in temperature of the water. The temperature rose by 12 °C for ethanol, by 18 °C for biodiesel and by 24 °C for kerosene. He tested each fuel once and concludes that kerosene is the best fuel.

   (a)

   Identify the independent variable and the dependent variable, and name two variables that Arjun must control.

   [3 marks]

   (b)

   Evaluate Arjun's conclusion that kerosene is the best fuel, and suggest two improvements to his method.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   The government of a Gulf country with large natural gas reserves and strong sunshine wants to reduce carbon dioxide emissions from road transport. Cars currently run on petrol. The energy released when 1 kg of fuel burns is about 46 MJ for petrol, 27 MJ for ethanol and 142 MJ for hydrogen. The government is considering two options: (1) replacing petrol with bioethanol made from imported crops, or (2) building solar-powered plants to make hydrogen for fuel-cell cars.

   (a)

   Compare petrol, ethanol and hydrogen as fuels for cars in terms of the energy released and their environmental effects.

   [6 marks]

   (b)

   Discuss and evaluate the government's two options for reducing carbon dioxide emissions from road transport.

   [6 marks]

   Total for question 4: 12 marks

End of questions