CombustionIB MYP Sciences: Subtopic test

1. 1
   A chef in Lagos cooks on a gas hob that burns natural gas, which is mainly methane. When the air holes at the base of the burner are open, the flame is blue and the pan stays clean. When the air holes are closed, the flame becomes yellow and the base of the pan is coated in a black deposit.

   (a)

   What is the black deposit on the pan?

   [1 mark]

   • ACarbon monoxide
   • BCarbon dioxide
   • CCarbon (soot)
   • DWater

   (b)

   Which products are made when methane burns completely?

   [1 mark]

   • ACarbon dioxide and water
   • BCarbon monoxide and water
   • CCarbon and water
   • DCarbon dioxide and hydrogen

   (c)

   Explain why the flame is yellow and produces a black deposit when the air holes are closed.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A family in Montreal runs a gas heater in a small bedroom during a cold winter. The windows are sealed to keep the heat in. During the night, a carbon monoxide alarm in the room sounds loudly.

   (a)

   Why is carbon monoxide dangerous to breathe in?

   [1 mark]

   • AIt reacts with oxygen in the air to make acid rain
   • BIt is toxic because it stops the blood carrying oxygen around the body
   • CIt explodes at room temperature
   • DIt makes the air in the room too hot to breathe

   (b)

   Why is carbon monoxide difficult for people to notice without an alarm?

   [1 mark]

   • AIt is bright yellow
   • BIt has a strong smell of rotten eggs
   • CIt is a liquid at room temperature
   • DIt is colourless and has no smell

   (c)

   Suggest two ways in which the family could reduce the risk of carbon monoxide poisoning.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   Alana, a student in Wellington, investigates how long a candle burns under glass jars of different volumes. She lights three identical candles, covers each with an upturned jar and times how long it takes for each flame to go out. The 250 cm³ jar gave 8 seconds, the 500 cm³ jar gave 17 seconds and the 1000 cm³ jar gave 33 seconds. She tested each jar once.

   (a)

   Describe the trend in Alana's results and explain it using the fire triangle.

   [3 marks]

   (b)

   Evaluate Alana's investigation, and suggest two improvements.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   An engineer in Perth designs gas-fired water heaters for homes. They burn methane (CH₄) and have air vents at the base. In tests, when the vents are partly blocked, the flame turns yellow and the heater gives off a poisonous gas. A regulator is considering a rule that every home with a gas appliance must have a carbon monoxide alarm and an annual safety service, both paid for by the householder.

   (a)

   Explain, using the fire triangle and equations, why blocking the vents changes the products of burning methane.

   [6 marks]

   (b)

   Discuss and evaluate the regulator's proposed rule that every home with a gas appliance must have a carbon monoxide alarm and an annual safety service.

   [6 marks]

   Total for question 4: 12 marks

End of questions