Putting Out Fire!

Well after lighting so many fires it was time to see how many different ways we could put one out.

We began by recapping what we knew about what fire needed and then investigated the 'Fire Triangle' which was a great visual for explaining the equivalent resources required.

The first investigation was to figure out the best way to take the 'heat' out of the fire (put out the candle flame) using a spray bottle of water. The consensus was that spraying from the side was largely ineffective compared to spraying from the top but best of all was found to be slower heavier drips from above. This led onto some students researching how fire sprinklers worked.

The next challenge was to remove the 'Oxygen' from the triangle. Students knew from their jar investigations one way of doing it so what was another? Once someone came up with an idea then others were keen to try it. There was plenty of dicsussion on how best to do this safely.

Using Carbon Dioxide (CO2) really got some students thinking. They enjoyed watching the reaction occur when combining the vinegar and baking soda. The question was why did the shorter of the two candles they had in the bowl go out? Most chose to repeat this experiment because it was fun but also to confirm that the result was consistent. Again they were successful in removing the Oxygen from the Fire triangle.

Using tinfoil to make a trough to 'pour' CO2  down provided a challenge for most. There was a very fine line between the gas travelling down to extinguish the candle and having all the liquid run down and drowning it instead. This investigation provided opportunities for great perseverance, team work, and visualisation. The students knew from the previous experiment that the gas was CO2 but how could it run downhill? Don't all gases float in the air? Those who were interested researched and confirmed some of their thoughts about CO2 being heavier than O2.

The grand finale of this session was flour. This didn't sound very exciting. When discussing the Fire triangle we had listed a huge range of various types of fuels on the whiteboard. I asked the question 'Is flour a fuel?' This was hotly debated with many different reasons for and against it. We all watched with anticipation as a student lit a match and dropped it into a bowl of flour. Nothing happened. So I demonstrated another way that we could experiment with by providing an increased amount of oxygen with the flour and heat this time. The results were amazing and everyone simply had to have a go!