Download Early Ideas About Matter

Section 4?t
Objectives
Compare and contrast the
atomic models of Democritus,
Aristotle, and Dalton.
Understand how Dalton’s theory
s.
explains the conservation of mas
Review Vocabulary
theory: an explanation supported
ject
by many experiments; is still sub
be
can
,
data
l
enta
to new experim
sful
modified, and Is considered succes
s
ion
dict
pre
e
mak
to
if it can be used
that are true
New Vocabulary
Dalton’s atomic theory
• Figure 4.1 Many Greek philosophers
thought that matter was composed of four
elements; earth, air, water, and fire. They
also associated properties with each ele
s,
ment. The pairing of opposite propertie mir
dr
and
wet
and
,
cold
and
hot
such as
re.
rored the symmetry they observed in natu
and
rrect
inco
e
These early ideas wer
non-scientific.
102
Chapter 4
•
The Structure of the Atom
Early Ideas About Matt,ebutrthe
eeks tried to explain matter
l’V1Ij The ancient Gr
early
began with John Dalton in the
scientific study of the atom
1800s.
eriment
tball team might practice and exp
Real-World Reading Link A foo
they
.
As
plan
e
develop the best-possible gam
with different plays in order to
the
team’s
ne
ches can make adjustments to refi
see the results of their plans, coa
with different
last 200 years have experimented
play. Similarly, scientists over the
.
models as they collected new data
models of the atom, refining their
Greek Philosophers
exist several thousand years ago.
Science as we know it today did not
few
experiment was, and there were
No one knew what a controlled
nd
mi
the
of
er
In this setting, the pow
tools for scientific exploration.
the
to
s
sidered the primary avenue
and intellectual thought were con
as
erest of scholarly thinkers known
truth. Curiosity sparked the int
cu
y
spe
the
As
.
life
of
s
many mysterie
philosophers who considered the
d
late
mu
for
ers
, many of the philosoph
lated about the nature of matter
life experiences.
explanations based on their own
matter was composed of things such
Many of them concluded that
wn in Figure 4.1. It was also com
as earth, water, air, and fire, as sho
r
ld be endlessly divided into smalle
monly accepted that matter cou
no
early ideas were creative, there was
and smaller pieces. While these
dity.
method available to test their vali
The Greek philosopher Democritus (460—370 Bc)
infinitely
:tpersonto propose the idea that matter was not
particles
individual
tiny
of
made
up
was
believed matter
derived.
Democritus
is
atom
English
word
:s from which the
be created, destroyed, or further divided.
“t atoms could not
his ideas are shown in Table 4.1.
of
summarY
ritus and a
1
ve1
s ideas do not agree with modern
DemocrituS’
a number of
his belief in the existence of atoms was amazingly ahead
a’Ic theorY,
met with criticism from other
time. However, his ideas were
the atoms together?” Democritus
holds
“What
asked,
iii1osoph who
question.
gould not answer the
Aristotle (384—322 B.C.), one
Aristotle Other criticisms came from
. He rejected the notion of
philosophers
Greek
of the most influential
with his own ideas about nature. One of
atoms because it did not agree
Aristotle’s major criticisms concerned the idea that atoms moved
through empty space. He did not believe that empty space could exist.
of
His ideas are also presented in Table 4.1. Because Aristotle was one
the most influential philosophers of his time, Democritus’s atomic
theory was eventually rejected.
In fairness to Democritus, it wa impossible for him or anyone else
of his time to determine what held the atoms together. More than two
thousand years would pass before scientists would know the answer.
However, it is important to realize that Dernocritus’s ideas were just
that—ideas, not science. Without the ability to conduct controlled
experiments, Democritus could not test the validity of his ideas.
Unfortunately for the advancement of science, Aristotle was able to
gain wide acceptance for his ideas on nature—ideas that denied the
existence of atoms. Incredibly, the influence of Aristotle was so great
and the development of science so primitive that his denial of the
existence of atoms went largely unchallenged for two thousand years!
tL5
VOCABULARY
WORD ORIGIN
Atom
comes from the Greek word atomos,
meaning indivisible
Reading Check Infer why it was hard for Democritus to defend
his ideas.
Table 4.1
Ancient Greek Ideas About Matter
Ideas
opher
1
i
Matter is composed of atoms, which move through empty space.
Atoms are solid, homogeneous, indestructible, and indivisible.
Different kinds of atoms have different sizes and shapes.
Size, shape, and movement of atoms determine the properties
of matter.
Democritus
(460—370 B.C.)
•
•
•
•
Aristotle
• Empty space cannot exist.
• Matter is made of earth, fire, ai and water.
(384-322
B.C.)
Section 4.1
•
Early Ideas About Matter 103
Dalton’s Atomic Theory
Table 4.2
Ideas
Scientist
—
atoms.
Matter is composed of extremely small particles called
.
Atoms are indivisible and indestructible
and chemical properties.
Atoms of a given element are identical in size, mass,
e of another element.
Atoms of a specific element are different from thos
to form compounds.
r
ratios
Different atoms combine in simple whole-numbe
bined or rearranged.
In a chemical reaction, atoms are separated, com
•
•
•
•
•
•
Dalton
(1766-1844)
-
ed in the
was reviv
John Dalton Although the concept of the atom
re significant
befo
s
year
red
eighteenth century, it took another hund
ry by John
centu
h
teent
progress was made. The work done in the nine
the
beginning
s
and, mark
Dalton (1766—1844), a schoolteacher in Engl
on revived and
of the development of modern atomic theory. Dalt
tific research he
scien
of
ts
resul
revised Democritus’s ideas based on the
are similar.
ideas
on’s
conducted. In many ways, Democritus’s and Dalt
Dalton
day,
ocritus’s
Thanks to advancements in science since Dem
to refine and support
was able to perform experiments that allowed him
ions, malcing care
react
ical
his hypotheses. He studied numerous chem
was able to deter
He
way.
ful observations and measurements along the
in those reactions. The
mine the mass ratios of the elements involved
atomic theory, which he
results of his research are known as Dalton’s
ry are summarized in
proposed in 1803. The main points of his theo
book, an extract of which is
Table 4.2. Dalton published his ideas in a
shown in Figure 4.2.
us’ and Dalton’s
Reading Check Compare arid contrast Democrit
ideas.
F%.e, 4
• Figure 4.2 In his book A New System
of Chemical Philosophy, John Dalton presented
his symbols for the elements known at that
time and their possible combinations.
J
00 0000
thé6éé
óàôàà th
I
000
0
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17
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JO
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/D0.
.
••
..
•. :•
•.
Atoms of Element A
Total mass = 4(Mass A)
‘I
-.
Atoms of Element B
Total mass = 8(Mass B)
p
Compound composed
of Elements A and B
Total mass = 4(Mass A) + 8(Mass B)
atoms of two or more elements combine to form a compound,
• Figure 4.3 When
element is conserved. Thus, the mass is conserved as well.
each
of
atoms
of
the number
Con5e1Iatb0I of mass Recall from Chapter 3 that the law of con
servation of mass states that mass is conserved in any process, such as
a chemical reaction. Dalton’s atomic theory easily explains that the con
servation of mass in chemical reactions is the result of the separation,
combination, or rearrangement of atoms—atoms that are not created,
destroyed or divided in the process. The formation of a compound
from the combining of elements and the conservation of mass during
the process are shown in Figure 4.3. The number of atoms of each
type is the same before and after the reaction. Dalton’s convincing
experimental evidence and clear explanation of the composition of
compounds, and conservation of mass led to the general acceptance
of his atomic theory.
Dalton’s atomic theory was a huge step toward the current atomic
model of matter. However, not all of Dalton’s theory was accurate. As is
often the case in science, Dalton’s theory had to be revised as additional
information was learned that could not be explained by the theory. As
you will learn in this chapter, Dalton was wrong about atoms being
indivisible. Atoms are divisible into several subatomic particles. Dalton
was also wrong about all atoms of a given element having identical
properties. Atoms of the same element can have slightly different masses.
Section 4I
Asses
Section Summary
I Democritus was the first person to
propose the existence of atoms.
I According to Democritus, atoms are
solid, homogeneous, and indivisible.
I Aristotle did not believe in the
existence of atoms.
I John Dalton’s atomic theory is based
Ofl numerous scientific
experiments.
Ch enst
line
1. iriic Contrast the methods used by the Greek philosophers and Dalton
to study the atom.
2. Define atom using your own words.
3. Summarize Dalton’s atomic theory.
4. Explain how Dalton’s theory of the atom and the conservation of mass are
related.
5. Apply Six atoms of Element A combine with eight atoms of Element B to pro
duce six compound particles. How many atoms of Elements A and B does each
particle contain? Are all of the atoms used to form compounds?
6. Design a concept map that compares and contrasts the atomic ideas proposed
by Democritus and John Dalton.
Self-Check Quiz lencoe.corn
Section 4.1
•
Early Ideas About Matter 105