Read the passage and identify the method being used. crude oil is a mixture of many liquids that must be separated into pure substances before we can use them. to do so, the entire mixture of liquids is heated in a furnace to 400 degrees celsius, which is enough to evaporate all of the liquids. then the mixed vapor is allowed to rise. as the vapor rises, it cools. when it reaches 370 degrees celsius, fuel oil condenses from the vapor and runs down a channel to be collected as a pure substance. however, the other vapors will continue to rise and cool. because the different substances in crude oil have different boiling points, each substance can be individually collected in the same way as fuel oil. where once we had a mixture of liquids, after condensing the various vapors, we have four different pure substances. which separation method is being used here?