Air, water, salt, gold, hydrogen, milk, oxygen, radium,
nitrogen, sulfur, baking soda, sodium, diamonds, sweetened
coffee, phosphorus, hydrochloric acid, brass.

INFERENCE EXERCISE

Explain the following:

431. Although in most electric lamps there is a vacuum between
the glowing filaments and the glass, the glass nevertheless
becomes warm.

432. Clothes left out on the line overnight usually become
damp.

433. You can separate water into hydrogen and oxygen, yet
you cannot separate the hydrogen or the oxygen into any other
substances.

434. Wet paper tears easily.

435. Windows are soiled on the outside much more quickly in
rainy weather than in clear weather.

436. If you stir iron and sand together, the iron will rust as
if alone.

437. Rust is made of iron and oxygen, yet you cannot separate
the iron from the oxygen with a magnet.

438. A reading glass helps you to read fine print.

439. Stretching the string of a musical instrument more
tightly makes the note higher.

440. Mayonnaise dressing, although it contains much oil, can
readily be washed off a plate with cold water.

SECTION 47. _Burning: Oxidation._

What makes smoke?

What makes fire burn?

Why does air keep us alive?

Why does an apple turn brown after you peel it?

If oxygen should suddenly lose its power of combining with other
things to form compounds, every fire in the world would go out at
once. You could go on breathing at first, but your breathing would be
useless. You would shiver, begin to struggle, and death would come,
all within a minute or two. Plants and trees would die, but they would
remain standing until blown down by the wind. Even the fish in the
water would all die in a few minutes,--more quickly than they usually
do when we take them out of the water. In a very short time everything
in the world would be dead.

Then suppose that this condition lasted for hundreds and hundreds of
years, the oxygen remaining unable to combine with other elements.
During all that time nothing would decay. The trees would stay as they
fell. The corpses of people would dry and shrivel, but they would lie
where they dropped as perfectly preserved as the best of mummies. The
dead fish would float about in the oceans and lakes.

This is all because life is kept up by burning. And burning is simply
the combining