HOW VAPOR IS CHANGED TO WATER
 HEAT, as you have learned, changes water into vapor. You must also know that cold turns vapor back
into water again.
Now let us think of the kettle with the boiling water. You will notice a little space; quite close
to the spout, where nothing can be seen. Is there no vapor there?
THINK OF THE KETTLE WITH THE BOILING WATER
Yes, there is vapor there, but it cannot be seen; it is invisible. A little way from the spout we
see something white, like smoke. This is only the vapor that has been chilled by the cool air and
changed back again into water. The water is in the form of very
 fine particles, and may be called water-dust.
Hold a cold plate over boiling water. Observe how the water-dust gathers into drops that roll down
You have seen the inside of windows in cold weather covered with moisture. Where does it come from?
Why did it form there? Why does it sometimes run down on the cold pane?
The vapor in our breath turns into water on frosty mornings. Explain this.
Carry a pitcher of ice-water into a room, and notice what takes place. A thin mist at once gathers
on the outside of the pitcher. What takes place among the little drops of mist? What becomes of
these larger drops?
Where does the water which collects on the outside of the pitcher come from? Does it come through
the pitcher from the inside? Would the same thing have taken place if some other cold object had
been used instead of a cold pitcher?
Write out what you have learned about vapor.
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