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Chapter 2 Notes

Chapter 2 Notes - Chapter 2 The Components of Matter...

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Slide No. 1 Chapter 2: The Components of Matter ± Elements ² Atoms (Discovery and Properties) ² Nuclear Symbols, Isotopes, Atomic Masses, and Ions ² Introduction to the Periodic Table ± Compounds ² Chemical formulas ² Types of compounds ² Chemical Nomenclature ² Molecular Masses ± Mixtures ± Reading Assignment: Entirety of Chapter 2. ± Homework Problems: 18(19), 22(23), 37(38), 39(40), 41(42), 45(46), 47(48), 54(55a-c), 56(57), 68(69), 84(85), 90(91), 94(95), 96(97), 106(107b,c),141 Lecture Outline Slide No. 2 2.1 Elements, compounds and mixtures ± Element: (Macroscopic concept) ² The simplest kind of substance – consists of only one type of atom ² e.g. "sodium" is a soft, lustrous metal that is easily oxidized ± Compound (Macroscopic concept) ² Substance made by chemical combination of 2 or more elements in a fixed ratio • Properties differ from those of the component elements • Converted to component elements by a _______ _______ • Macroscopic – methane is a colorless, combustible gas ± Atom (microscopic object) ² Smallest particle of an element that retains its chemical nature and uniqueness ² Symbol: 1-2 letters, 1st CAPS, 2nd lowercase ² e.g. "sodium" is an atom that is easily oxidized ± Molecule (microscopic object) ² methane has one C and four H atoms. ² An element can appear as a bunch of molecules (e.g. O 2 ) ± Mixture (macroscopic object) ² Physical combination of elements and/or compounds ² The composition is not ____, so unlike elements and compounds they do not constitute a substance
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Slide No. 3 2.2 Observations Leading to the Atomic Theory ± 400 BC ² Democritus proposes existence of the atomos (Gr. "indivisible"). ² Aristotle disputes theory – and thus the theory is ignored for 2000 y. ± 18th Century: Early Laws ² Conservation of Mass : The total ____ of all substances involved in a chemical reaction does not change during the chemical reaction. ² Definite Composition : No matter what its source, a given compound is composed of the same elements in the same ratios by mass. (More mass ratios on next slide) ² Multiple Proportions (Dalton's Law) : If elements A and B react to form two different compounds , the different masses of B that combine with a fixed mass of A can be expressed as a ratio of small whole numbers. 12 g of C combine with 16 g of oxygen (giving CO) 12 g of C combine with 32 g of oxygen to give a different substance (CO 2 ) 32/16 = 2 (a small whole number) 28 g of N 2 combine with 16 g of O 2 (giving N 2 O) 28 g of N 2 combine with 64 g of O 2 (giving NO 2 ). 64/16 = 4 (a small whole number) Slide No. 4 Mass Fraction ± Example: ² A 25.0 g sample of potassium sulfate is found to have 11.2 g K, 4.6 g S, and 9.2 g O. Calculate the mass fraction and percent by mass of each element. mass fraction (A) = mass of A total mass of compound percent (A) = fraction (A) x 100 element mass (g) mass fraction % by mass K 11.2 0.448 44.8 O9 . 2 0.368 36.8 S4 . 6 0.184 18.4 total 25.0 1.000 100.0 Example in text on p. 42. Also Sample Problem 2.1 on p. 43 2.2 Observations Leading to the Atomic Theory
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Slide No. 5 2.3 Dalton's Atomic Theory 1. All matter is composed of atoms.
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Chapter 2 Notes - Chapter 2 The Components of Matter...

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