q: about Bunsen burners

There’s something I don’t understand about how bunsen burners work. Gas and air are mixed to form a hot flame- but why doesn’t the point of ignition back up to where the gas and air first come into contact?

Pretty simple… the gas and air meet down in the tube, and are propelled to the orfice where they actually mix from the turbulence the opening creates. Also, ambient oxygen in the air outside of the tube is required for complete combustion.