CombustionIB MYP Sciences: Mind map

Exam questions on Combustion

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.
   Explain why the flame is yellow and produces a black deposit when the air holes are closed.2 marks
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.
   Suggest two ways in which the family could reduce the risk of carbon monoxide poisoning.2 marks
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.
   Describe the trend in Alana's results and explain it using the fire triangle.3 marks