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Flashcards in Ch 3 Section 1 Deck (31):

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