Air pressure and boiling temperature

Under standard conditions water boils at about 100°C. In the mountains the boiling point is lower. On Mount Zugspitze (height: 2.962m ) water would boil at 90°C, on Mount Everest at 70°C. At the Dead Sea, however, the boiling point exceeds 100°C. What are the reasons for these different values? To answer this question, you should perform the following experiment.
Experiment   

1.     5 mL of water are heated to boiling in an ampoule placed on a stand above a candle burner. This stand is the wire of a sparkling wine closure.                                                                     (more see below)