An Elementary Study of Chemistry | Page 6

26° to elements which do not melt
save in the intense heat of the electric furnace.
~Occurrence of the elements.~ Comparatively few of the elements
occur as uncombined substances in nature, most of them being found in
the form of chemical compounds. When an element does occur by itself,
as is the case with gold, we say that it occurs in the free state or native;
when it is combined with other substances in the form of compounds,
we say that it occurs in the combined state, or in combination. In the
latter case there is usually little about the compound to suggest that the
element is present in it; for we have seen that elements lose their own
peculiar properties when they enter into combination with other
elements. It would never be suspected, for example, that the reddish,
earthy-looking iron ore contains iron.
~Names of elements.~ The names given to the elements have been

selected in a great many different ways. (1) Some names are very old
and their original meaning is obscure. Such names are iron, gold, and
copper. (2) Many names indicate some striking physical property of the
element. The name bromine, for example, is derived from a Greek
word meaning a stench, referring to the extremely unpleasant odor of
the substance. The name iodine comes from a word meaning violet,
alluding to the beautiful color of iodine vapor. (3) Some names indicate
prominent chemical properties of the elements. Thus, nitrogen means
the producer of niter, nitrogen being a constituent of niter or saltpeter.
Hydrogen means water former, signifying its presence in water. Argon
means lazy or inert, the element being so named because of its
inactivity. (4) Other elements are named from countries or localities, as
germanium and scandium.
~Symbols.~ In indicating the elements found in compounds it is
inconvenient to use such long names, and hence chemists have adopted
a system of abbreviations. These abbreviations are known as symbols,
each element having a distinctive symbol. (1) Sometimes the initial
letter of the name will suffice to indicate the element. Thus I stands for
iodine, C for carbon. (2) Usually it is necessary to add some other
characteristic letter to the symbol, since several names may begin with
the same letter. Thus C stands for carbon, Cl for chlorine, Cd for
cadmium, Ce for cerium, Cb for columbium. (3) Sometimes the symbol
is an abbreviation of the old Latin name. In this way Fe (ferrum)
indicates iron, Cu (cuprum), copper, Au (aurum), gold. The symbols
are included in the list of elements given in the Appendix. They will
become familiar through constant use.
~Chemical affinity the cause of chemical combination.~ The agency
which causes substances to combine and which holds them together
when combined is called chemical affinity. The experiments described
in this chapter, however, show that heat is often necessary to bring
about chemical action. The distinction between the cause producing
chemical action and the circumstances favoring it must be clearly made.
Chemical affinity is always the cause of chemical union. Many
agencies may make it possible for chemical affinity to act by
overcoming circumstances which stand in its way. Among these

agencies are heat, light, and electricity. As a rule, solution also
promotes action between two substances. Sometimes these agencies
may overcome chemical attraction and so occasion the decomposition
of a compound.
EXERCISES
1. To what class of changes do the following belong? (a) The melting
of ice; (b) the souring of milk; (c) the burning of a candle; (d) the
explosion of gunpowder; (e) the corrosion of metals. What test question
must be applied in each of the above cases?
2. Give two additional examples (a) of chemical changes; (b) of
physical changes.
3. Is a chemical change always accompanied by a physical change? Is a
physical change always accompanied by a chemical change?
4. Give two or more characteristics of a chemical change.
5. (a) When a given weight of water freezes, does it absorb or evolve
heat? (b) When the resulting ice melts, is the total heat change the same
or different from that of freezing?
6. Give three examples of each of the following: (a) mechanical
mixtures; (b) chemical compounds; (c) elements.
7. Give the derivation of the names of the following elements: thorium,
gallium, selenium, uranium. (Consult dictionary.)
8. Give examples of chemical changes which are produced through the
agency of heat; of light; of electricity.
CHAPTER II
OXYGEN
~History.~ The discovery of oxygen is generally attributed to the

English chemist Priestley, who in 1774 obtained the element by heating
a compound of mercury and oxygen, known as red oxide of mercury. It
is probable, however, that the Swedish chemist Scheele had previously
obtained it, although an account of his experiments was not published
until 1777. The name oxygen signifies acid former.