1 Extensive properties of a pure substance depend on sample size whereas intensive properties are characteristic of substance. Which of these properties are intensive?I) ColorII) MassIII) Density that A) I and IIB) I and IIIC) II and IIID) I, II and III
2 Atomic Theory • Several key observations lead to the theory of atoms • Law of the conservation of Matter : Mass is neither created or destroyed in chemical process • It is just moved around • Limits possibilities of chemical reactions • Leads directly to . . . • Law of multiple proportions : When two elements form a series of compounds, the ratio of the masses of each elements can always be reduced to a whole number
Atomic Theory • Nature only allows certain combinations of masses • Combination of atoms • Oxygen and hydrogen mostly react with the ratio : 8 ? ?????? 1 ? ℎ ??????? • Can write Molecular formula of water as H 2 O: 2 mol hydrogen (mass 1g each) and one mol oxygen (16g) = 16 ? ?????? 8 ? ?????? 3 2 ? ℎ ??????? 1 ? ℎ ???????
What is an atom? and
5 The amu • Atoms so small special unit used to describe their mass • amu → atomic mass unit • 1 amu = 1.6606x10 -24 g • Value set so carbon-12 atom has mass of exactly 12.0 amu
e - p + n 0 Hydrogen 1.0078 amu Hydrogen 2.0140 amu Hydrogen Ion 1.0072 amu Carbon 6p + 6n 0 12 amu Carbon 6p + 7n 0 13.0034 amu Carbon ion 6p + 6n 0 11.9994 amu 6
e - p + n 0 Hydroge n Hydroge n Hydrogen Ion Carbon 6p + 6n 0 Carbon 6p + 7n 0 Carbon ion 6p + 6n 0 1.0078 amu 2.0140 amu 1.0072 amu 12 amu 13.0034 amu 11.9994 amu ? How many protons are in How many neutrons are in How many electrons are in , , and , , and , , and 6, 6, and 6 ? 6, 7, and 6 ? 6, 6, and 7 7
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- Spring '08