2. CONDENSATION OF VAPOUR
Analysis, or selection:
The pupils should be asked to report observations they have made concerning some familiar occurrences like the following:
(1) Breathe upon a cold glass and upon a warm glass. What do you notice in each case? Where must the drops of water have come from? Can you see this water ordinarily? In what form must the water have been before it formed in drops on the cold glass?
(2) What have you often noticed on the window of the kitchen on cool days? From where did these drops of water come? Could you see the vapour in the air? How did the temperature of the window panes compare with the temperature of the room?
(3) When the water in a tea-kettle is boiling rapidly, what do you see between the mouth of the spout and the cloud of steam? What must have come through that clear space? Is the steam then at first visible or invisible?
The pupils should be further asked to report observations and make correct inferences concerning such things as:
(4) The deposit of moisture on the outside surface of a pitcher of ice-water on a warm summer day.
(5) The clouded condition of one's eye-glasses on coming from the cold outside air into a warm room.
Comparison, Abstraction, and Generalization, or Organization: