1. What is Natural Philosophy or Physics?
Natural Philosophy or Physics is the branch of science
that treats of matter, and of the forces operating upon
it, and of the physical changes thereby produced.
2. What is science?
Science is classified knowledge.
3. What is matter ?
Matter is anything that takes up room.
4. Is this a real definition of Matter?
It is not, for it simply tells something about matter in-
stead of telling what matter really is.
5. Why then is it given ?
Because, in the present state of human knowledge, we
can tell nothing of the real nature of matter and this
does the next best thing ; it enables us to distinguish
matter from that which is not matter.
6. Give some other " definition " of matter.
Matter is anything that has weight
7. What are the divisions of matter?
Atoms, molecules, and masses.
8. What is an atom ?
The smallest quantity of matter that can enter into com-
bination. It is generally a part of a molecule.
9. How many kinds of atoms are there?
As many as there are " elements," of which we now know
more than seventy. Others will probably be found.
10. Can an atom be divided ?
Atoms are considered indivisible, but the form or consti-
tution of an atom is unknown. The atom is the chemi-
cal unit of matter.
11. What is a molecule?
It is the smallest quantity of matter that can have a sep-
12. How many kinds of molecules are there?
As many as there are kinds of matter. The nature of
the molecule determines the nature of the substance of
which it is a part.
13. Can a molecule be divided ?
Yes, but. only by a chemical process. A molecule is the
physical unit of matter.
14. Give an illustration of a molecule,
A particle of sugar so small that, if it is divided, none of
Its parts will be sugar.
15. What are the parts of a molecule called?
16. How many atoms are there in a molecule ?
Chemistry teaches that in the case of a very few of th«
elements, the molecule consists of a single atom, but
in almost every case, the molecule contains two or
more atoms. The common sugar molecule has 45
atoms ; the oxygen molecule has two atoms.
17. What is a mass?
A body of matter consisting of two or more molecules;
it is not necessarily very massive.
18. Give an illustration of a** mass " of matter,
A minute dust speck, a mountain or a planet
19. What is an element or an elementary substance ?
A substance, all of the atoms of which are alike, /. e,, one
composed of a single kind of atoms. Silver is an ele-
ment because all of its atoms are silver atoms ; it can-
not by any known or conceivable process be " analysed "
20. What is a compound substance ?
One that contains more than one kind of atoms. One of
its molecules is like its other molecules, but each mole-
cule contains more than one kind of atoms. Thus, a
dew-drop is composed of many similar water molecules.
but each of the molecules is composed of one oxygen and
two hydrogen atoms. Hence, water in any quantity is
a compound substance. Compound substances are in-
21. What is a physical change ?
One that does not change the structure of the molecule
of which the changed body is composed.
22. Illustrate the meaning of " physical change. "
A black iron nail may be made red-hot. The iron mole-
cules jostle one another more vigorously than before,
and the energy of their mutual thrusts we call heat. A
certain kind of motion produced by such increased
activity of the molecules we call light, but the mole-
cules themselves are simply iron molecules, just as
they were at first. The molecule is one thing; the
motion of the molecule is a wholly different thing.
By increasing the molecular motions^ we may even
melt the iron, but that will not change the mole-
cules ; it will simply be melted iron. Two such nails
may be united by welding. The identical molecules
are preserved, and with unchanged identity. With a
file, some of these may be torn away from others, but
each of the filings will be /V^w-filings, composed of un-
changed iron molecules. Hence all of these are physi-
23. With this idea of heat as a mode of motion give another
definition of molecule,
A molecule is an aggregation of material particles that
do not part company during the journey of a heat vi-
24. State and illustrate some change of matter that is not a
If the iron is treated with sulphuric acid, the iron atoms
in each iron molecule will be torn asunder. Each iron
atom will be joined to an atom of sulphur, and four
atoms of oxygen, to make a molecule of iron-sulphate
(green vitriol). We no longer have an iron molecule,
and hence, no iron. Iron and iron-sulphate are essen-
tially diflFerent. Changes that thus alter the constitu-
tion of the molecule, and hence, the nature of the sub-
stance, are chemical changes.
25. What objection is there to the term " Natural Philosophy ? "
There is a philosophy of mind as well as a philosophy of
matter, and one pertains as mostli to Nature as the
other. But the term "Natural Philosophy," with its
restricted significance, is so completely worked into
our language and literature that it would be difficult to
change the usage. The term ** Physics " is preferable.