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 an 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)