The Science of Fire

It’s about time to start enjoying a cup of hot cocoa around the fire on these chilly fall days and evenings. For some, fires make us think of s’mores, camping, or gathering with friends and family. For others, it makes us think of SCIENCE!

So, what is the science behind fires? It is actually quite simple: Oxygen + Fuel + Heat = Fire, as displayed in our fire triangle:

If any one component is missing, you won’t have fire!

When we think of a traditional campfire, the fuel is wood and the heat source is a match or lighter.

Let’s do an experiment to see the fire triangle in action.

Experiment CO2 Fire Extinguisher

Materials:

  • Baking soda
  • Vinegar
  • Pitcher or large cup
  • Tea light
  • Lighter

Set up: Light the candle and ask students if they think there is a way to put it out with the ingredients they see.    

Conduct Experiment: Pour some vinegar and baking soda into the pitcher / cup.  Wait a few moments for the reaction to taper off and slowly pour the “air” from the container (not the liquid) over the flame and watch the flame go out. 

The Science: If one of the three components of the fire triangle are removed, the flame will go out.  When the baking soda (a base) and the vinegar (an acid) interact, a reaction occurs and a new substance, carbonic acid, is produced.  Carbonic acid doesn’t last long – it breaks down into carbon dioxide (CO2) and water (H2O).  The “bubbles” inside the container are the production of CO2 (a gas).  The CO2 gas is heavy, so it can be poured just like a liquid.  The CO2 takes over the “air” space near the flame, causing it to be deprived of oxygen, and thus causing the flame to extinguish!  In this experiment, oxygen is the missing component of the fire triangle.    

**Remember only experienced adults should conduct experiments involving fire.**