Where is the burner on stage 5 of Questionaut

The burner is the large contraption you are using to boil the water: it burns gas, either propane or natural gas, to heat materials in the laboratory.

Click the icicle and drop it into the flask (a retort). Turn the wheel at the bottom counterclockwise twice (the gas is flowing). Click the matches and take one out, and strike it on the side of the box. Click at the base of the flask and the burner will ignite, heating the icicle which first melts then boils into steam to turn the little propellor and lift the plug. Click the skater when he is near the pole to ask questions.