Final answer:
A fire will burn faster in a higher-than-normal concentration of oxygen because oxygen is a reactant in combustion, and increasing its concentration increases the reaction rate.
Step-by-step explanation:
A fire in the presence of a higher-than-normal concentration of oxygen will generally burn faster than normal. The reason for this lies in the principles of chemical reactions where the increase in the concentration of a reactant, which in this case is oxygen, will increase the rate of the reaction. Thus, when you have a higher concentration of oxygen, the combustion process is accelerated. Using the example of a wooden splint: in normal air, which is about 20% oxygen, the splint after being ignited and blown out will glow. However, introduce the glowing splint to an environment with a higher oxygen concentration, and it will burst back into flame due to the increased reaction rate. This is because the oxygen serves as one of the reactants in the combustion reaction, and with more of it available, the reaction proceeds much more quickly. Another illustration is phosphorus which burns rapidly in air but will burn even more rapidly if the concentration of oxygen is higher. This occurs because higher oxygen levels support faster and more energetic combustion processes.