Ch 3 Section 1 Flashcards
Democritus called natures basic particle an
Atom based on Greek word meaning “indivisible”
Aristotle thought that all matter was
Continuous and his opinion was accepted for nearly 2000 years
Neither the view of Aristotle nor that of Democritus was supported by
Experimental evidence do each remained speculation until the 18th century
Virtually all c he jets in the late 1700s accepted the modern definition of an element as a
Substance that cannot be further broken down by ordinary chemical means
It was clear that elements combine to form
Compounds that have different physical and chemical properties than those of the elements that form them
Great controversy as to whether elements
Always combine in the same ratio when forming a compound
Chemical reaction
Transformation of a substance(s) into one or more new substance
Particle theory of matter was was supported as early as
400 BC by Greek thinkers such as Democritus
Study of matter was revolutionized by a new emphasis on the
Quantitative analysis of chemical reactions
Aided by improved balances investigators began to
Accurately measure the masses of elements and compounds
Measurement of masses of elements and compounds led to the discovery of
Several basic laws
Law of conservation of mass
Mass is neither created nor destroyed during ordinary chemical reactions or physical changes
Discovery followed by assertion that regardless of where or how a pure chemical compound is prepared it is
Composed of a fixed proportion of elements
Law of definite proportions
Fact that a chemical compound contains the same elements in exCtly the same proportions by mass regardless of size of sample or source of compound
Known that 2 elements sometimes combine to form
More than one compound
Law of multiple proportions state that if two or more different compounds are composed of the same 2 elements then the ratio of the
Masses of the second element combined with a certain mass of the first element is always a ratio of small whole numbers
Dalton in 1808 proposed an explanation for the
Law of conservation of mass
The law of definite proportions
The law of multiple proportions
Dalton stated that elements were composed of
Atoms and that only whole numbers of atoms can combine to form compounds
(Daltons theory) all matter composed of extremely
Small particles called atoms
(Daltons theory) atoms of a given element are
Identical in size mass and other properties
(Daltons theory) atoms of different elements differ in
Size mass and other properties
(Daltons theory) atoms cannot be
Subdivided created or destroyed
(Daltons theory) atoms of different elements combine in
Simple whole number ratios to form chemical compounds
(Daltons theory) in chemical reactions atoms are
Combined separated or rearranged
According to dalton a theory the law of conservation of mass is explained by the fact that chemical reactions merely involve the
Combination separation or rearrangement of atoms and that during these processes atoms are not subdivided created or destroyed
Law of definite proportions results from the fact that a given chemical compound is always composed of the
Same combination of atoms
In the case of carbon oxides for law of multiple proportions, 2 to 1 ratio of oxygen masses results because CO2 always contains
Twice as many oxygen atoms as does carbon monoxide
By relating atoms to measurable property of mass dalton turned Democritus idea into a
Scientific theory that could be tested by experiment
Today we know that atoms are
Divisible into even smaller particles
We also know that a given element can have
Atoms with different masses
Daltons ideas that remain unchanged:
All matter is composed of atoms
Atoms of any one element differ in properties from atoms of another element
