Burning oxygen - how much oxygen is required to sustain a flame

Introduction

Three elements must be present at the same time for a flame to burn:

• Fuel
• Oxygen
• Heat

If any of these elements are reduced or removed then a flame will be extinguished. This experiment uses the DrDAQ’s Oxygen In Air sensor to monitor the oxygen level required to keep a flame burning.

Warning — as this experiment requires the use of matches adult supervision will be required.

Equipment required (See Fig. 1)

• PC with PicoLog data logging software installed
• DrDAQ
• Oxygen in air sensor (DD103)
• Temperature sensor (DD100)
• Bowl of water
• Glass jar
• Dark room (for light sensor)

Fig1: Setup

Equipment setup

• Connect the DrDAQ data logger to the parallel port.
• Attach the oxygen and temperature sensors to the top of the glass jar. Keep all the sensor leads a safe distance away from the candle.
• Connect the oxygen in air sensor DD103 and the temperature sensor DD100 to external sockets 1 and 2.
• Configure PicoLog to take a sample every 250 milliseconds for 200 samples.

Carrying out the experiment

• Start PicoLog recording
• Light the candle
• Place the glass jar with the sensors attached over the bowl of water (As seen in Fig. 1)
• Hold the DrDAQ’s onboard light sensor to the glass jar
• Once the candle has been extinguished leave the experiment to settle for a couple of seconds

Questions

1. What two by-products were produced by the flame?
2. At what point did the candle extinguish?
3. How does the graph show you that the candle uses oxygen?
4. What oxygen level is required to keep the candle burning?