Final answer:
One spark is enough to ignite propane gas because it is a highly flammable fuel with a low ignition temperature. The heat generated from the initial spark sustains the burning of propane.
Step-by-step explanation:
When it comes to igniting propane gas, one spark is enough to start the combustion reaction. This is because propane is a highly flammable fuel that has a low ignition temperature, meaning it can easily catch fire when exposed to a spark or flame. Once the initial spark ignites the propane gas, the combustion reaction produces heat, carbon dioxide, and water vapor. The heat generated from the reaction sustains the burning of propane, so no more sparks are needed to keep it burning.