When the water vapor mixes with the cold air in the lower part of the bottle, the air becomes supersaturated, meaning that the water vapor will condense as ice onto any convenient object.
(the water vapor; mixes; with the cold air in the lower part of the bottle) (the air; becomes; supersaturated; T:When the water vapor mixes with the cold air in the lower part of the bottle)
the water vapor the air
mixes becomes
with the cold air in the lower part of the bottle
supersaturated T:When the water vapor mixes with the cold air in the lower part of the bottle