To switch to the blue flame on a Bunsen burner, you must turn the collar to open the _________ _________. What two word phrase completes this sentence?

To switch to the blue flame on a Bunsen burner, you must turn the collar to open the air vent.

The air vent allows air to mix with the gas before it ignites, which creates a hotter and cleaner flame. When the collar is turned to open the air vent, more oxygen enters the mixing chamber, resulting in complete combustion. This increase in oxygen reduces the amount of unburned carbon particles, producing a blue flame. The blue flame is characterized by its higher temperature and is often preferred in laboratory settings for heating substances since it provides a more controlled and efficient heat source. Closing the air vent leads to a yellow flame, which is cooler and has a luminous appearance due to incomplete combustion.