WAEC - Chemistry (2018 - No. 14)
Pure water can be made to boil at a temperature lower than 100°C by
reducing its quantity
decreasing the external pressure
distilling it
increasing the external pressure
Explication
The easiest and most drastic way to change the boiling point is by tampering with the pressure above your water. To lower the boiling point, you need simply to decrease its external pressure.