A Bunsen burner was a piece of laboratory equipment used to heat substances.
The First Doctor compared trying to explain the mechanics of time travel to Ian to teaching a primate the principles of a Bunsen burner — "the human mind is simply not equipped to deal with four-dimensional physics." (PROSE: The Witch Hunters)
When Captain Mike Yates secretly made hot cocoa in the Third Doctor's lab, he used his Bunsen burner. The heat from the burner activated a Auton troll doll the Doctor had taken from Mary Farrel, and it attacked Jo Grant. However, Yates shot the doll several times with his pistol, destroying it. (TV: Terror of the Autons)