Experiment 89. Hold a saucer of ice just below your mouth. Open your mouth wide and breathe gently over the ice. Can you see your breath?
Now put the ice into half a glass of water and cover the glass. Be sure the outside of the glass is thoroughly dry. Set it aside and look at it again in a few minutes.
What caused the mist when you breathed across the ice?
Where did the water on the outside of the glass of ice water come from? What made it condense?
Application 66. Explain why clouds are formed high in the atmosphere; why we have dew at night instead of in the daytime; why clothes dry more quickly in a breeze than in still air; why clothes dry more quickly on a sunny day than on a foggy one.
Inference Exercise
Explain the following:
411. A gas-filled electric lamp gets hotter than a vacuum lamp.
412. You can remove a stamp from an envelope by soaking it in water.
Fig. 159. The glass does not leak; the moisture on it comes from the air.
413. We see our breath on cold days and not on warm days.
414. The electric arc is exceedingly hot.
415. Rock candy is made by hanging a string in a strong syrup left open to the air.
416. Dishes in which candy has been made should be put to soak.
417. Moisture gathers on eyeglasses when the wearer comes from a cold room into a warm one.
418. Sprinkling the street on a hot day makes the air cool.
419. You cannot see things in a dark room.
420. Where air is rising there is likely to be rain.
Section 45. Softening due to oil or water.
Why does fog deaden a tennis racket?
How does cold cream keep your face from becoming chapped?
Let us now imagine that animal and plant substances have suddenly lost their ability to be softened by oil or water.