Which is the most important question for deciding if a chemical reaction has occurred?

Since we've been using petroleum in vast amounts organizations such as OPEC have appeared which restricts the U.S which ensued our country into suing; if this lawsuit passes then we will possibly be taking more petroleum than ever before due to it's demand such as it's needed for machinery and vehicles and etc. Most petroleum are from middle eastern countries, so our dependency will run rampant which will make us adhere to any of their policies pertaining to this fossil fuel in the near future.