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CHEMISTRY. Dr. Shyh-ching Yang. Chemistry, 6e. Steven S. Zumdahl 歐亞書局有限公司 楊 士 慶. Chapter 1(a). Chemical Foundations. Introduction: Chemistry is around you all the time. Prof. Luis W. Alvarez solved the problem of the disappearing dinosaurs. --- iridium 銥 77 Ir
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CHEMISTRY Dr. Shyh-ching Yang
Chemistry, 6e • Steven S. Zumdahl • 歐亞書局有限公司 楊 士 慶
Chapter 1(a) Chemical Foundations
Introduction: Chemistry is around you all the time • Prof. Luis W. Alvarez solved the problem of the disappearing dinosaurs. --- iridium 銥 77Ir --- niobium 鈮 41 Nb • Decline of Roman Empire --- A sweet syrup called “ Sapa” Boiling down grape juice in a lead-lined vessels, and cooled it down. It is the reason for Sapa’s sweetness. It was “lead acetate”. • Story of David & Susam --- Porphyria 一種稀有的血液疾病 • Low cobalt level 27Co, could be result in personality disorder and violent behavior. • Lithium salts have been shown to be very effective in controlling the effects of manic狂噪depressive憂鬱disease.
Chemistry: A Science for the 21st Century • Health and Medicine • Sanitation衛生 systems • Surgery with anesthesia麻醉 • Vaccines 疫苗and antibiotics抗生素 • Energy and the Environment • Fossil fuels • Solar energy • Nuclear energy 1.1
Chemistry: A Science for the 21st Century • Materials and Technology • Polymers, ceramics, liquid crystals • Room-temperature superconductors? • Molecular computing? • Food and Agriculture • Genetically modified crops • “Natural” pesticides殺蟲劑 • Specialized fertilizers肥料 1.1
（1.1). Chemistry: An Overview • What is matter made of ? – Atoms • Very recently for the first time we can “see” individual atoms—via STM (Scanning Tunneling Microscope) • One of the main challenges of chemistry is to understand the connection between the macroscopic world that we experience and the microscopic world of atoms and molecules.
Figure 1.01b: An oxygen atom on a gallium 31Ga鎵arsenide 33As砷 surface.
Figure 1.01c: Scanning tunneling microscope image showing rows of ring-shaped clusters(串) of benzene molecules on a rhodium 45Rh銠surface.
Figure 1.3: Sand on a beach looks uniform from a distance, but up close the irregular sand grains are visible.
(1.2) Steps in the Scientific Method(P.6) 1. Observations quantitative( involves both a number and a unit) qualitative（does not involve a number) 2. Formulating hypotheses possible explanation for the observation 3. Performing experiments gathering new information to decidewhether the hypothesis is valid
Outcomes(結果） Over the Long-Term Theory (Model) A set of tested hypotheses that give an overall explanation of some natural phenomenon. Natural Law The same observation applies to many different systems Example - Law of Conservation of mass
Law（定律） v. Theory • A law summarizes what happens; • A theory (model) is an attempt to explain why it happens.
Nature of Measurement • Measurement - quantitative observation consisting of 2 parts *Part 1 –number *Part 2 - scale (unit) • Examples: * 20 grams * 6.63 Joule seconds
(1.3) Unit of Measurement • International System Based on metric system and units derived （取得）from metric system.
Chemistry In Action On 9/23/99, $125,000,000 Mars Climate Orbiter entered Mar’s atmosphere 100 km lower than planned and was destroyed by heat. 1 lb = 1 N 1 lb = 4.45 N “This is going to be the cautionary tale that will be embedded （深留腦中）into introduction to the metric system in elementary school, high school, and college science courses till the end of time.” 1.7
Figure 1.7: Common types of laboratory equipment used to measure liquid volume.
Figure 1.9: Measurement of volume using a buret. The volume is read at the bottom of the liquid curve (called the meniscus(新月).
(1.4) Uncertainty in Measurement • A digit that must be estimated is called uncertain. A measurement always has some degree of uncertainty.
Figure 1.10: The results of several dart throws show the difference between precise（精確）and accurate（準確）.
Accuracy – how close a measurement is to the true value Precision – how close a set of measurements are to each other accurate & precise precise but not accurate not accurate & not precise 1.8
The number of atoms in 12 g of carbon: 602,200,000,000,000,000,000,000 The mass of a single carbon atom in grams: 0.0000000000000000000000199 Scientific Notation 6.022 x 1023 1.99 x 10-23 N x 10n N is a number between 1 and 10 n is a positive or negative integer 1.8
move decimal left move decimal right Scientific Notation 568.762 0.00000772 n > 0 n < 0 568.762 = 5.68762 x 102 0.00000772 = 7.72 x 10-6 Addition or Subtraction • Write each quantity with the same exponent n • Combine N1 and N2 • The exponent, n, remains the same 4.31 x 104 + 3.9 x 103 = 4.31 x 104 + 0.39 x 104 = 4.70 x 104 1.8
Scientific Notation Multiplication • Multiply N1 and N2 • Add exponents n1and n2 (4.0 x 10-5) x (7.0 x 103) = (4.0 x 7.0) x (10-5+3) = 28 x 10-2 = 2.8 x 10-1 Division • Divide N1 and N2 • Subtract exponents n1and n2 8.5 x 104÷ 5.0 x 109 = (8.5 ÷ 5.0) x 104-9 = 1.7 x 10-5 1.8
Precision（精密度）and Accuracy（準確度） • Accuracy refers to the agreement of a particular value with thetruevalue. • Precisionrefers to the degree of agreement among several elements of the same quantity.
Types of Error • Random Error (Indeterminate不能確定的 Error) - measurement has an equal probability of being high or low. • Systematic Error (Determinate Error) - Occurs in the same directioneach time (high or low), often resulting from poor technique.
(1.5) Significant Figures and Caculations:Rules for Counting Significant Figures - Overview • 1. Nonzero integers • 2. Zeros • leading zeros( does not count as significant figures) ex. 0.0025 ( 2 sig.) • captive (中間）zeros (yes) ex. 1.008 ( 4sig.) • trailing(尾數）zeros ex. 100 (1 sig.); 100.(3 sig.) 1.00*10**2 (3 sig.) • 3. Exact numbers(精確數字）
Rules for Counting Significant Figures - Details • Nonzero integersalways count as significant figures. • 3456 has • 4 sig figs.
Rules for Counting Significant Figures - Details • Zeros • Leading zeros do not count as • significant figures. • 0.0486 has • 3 sig figs.
Rules for Counting Significant Figures - Details • Zeros • Captive zeros always count as • significant figures. • 16.07 has • 4 sig figs.
Rules for Counting Significant Figures - Details • Zeros • Trailing zeros are significant only • if the number contains a decimal point（小數點）. • 9.300 has • 4 sig figs.
Rules for Counting Significant Figures - Details • Exact numbershave an infinite number of significant figures. • 1 inch = 2.54 cm, exactly
Significant Figures • Zeros between nonzero digits are significant • Any digit that is not zero is significant • 1.234 kg 4 significant figures • 606 m 3 significant figures • Zeros to the left of the first nonzero digit are not significant • 0.08 L 1 significant figure • If a number is greater than 1, then all zeros to the right of the decimal point are significant • 2.0 mg 2 significant figures • If a number is less than 1, then only the zeros that are at the end and in the middle of the number are significant • 0.00420 g 3 significant figures 1.8
How many significant figures are in each of the following measurements? 4 significant figures 3001 g 0.0320 m3 3 significant figures 6.4 x 104 molecules 2 significant figures 560 kg 2 significant figures 2 significant figures 24 mL 1.8
Significant Figures 89.332 + 1.1 one significant figure after decimal point two significant figures after decimal point 90.432 round off to 90.4 round off to 0.79 3.70 -2.9133 0.7867 Addition or Subtraction The answer cannot have more digits to the right of the decimal point than any of the original numbers. 1.8
3 sig figs round to 3 sig figs 2 sig figs round to 2 sig figs Significant Figures Multiplication or Division The number of significant figures in the result is set by the original number that has the smallest number of significant figures 4.51 x 3.6666 = 16.536366 = 16.5 6.8 ÷ 112.04 = 0.0606926 = 0.061 1.8
6.64 + 6.68 + 6.70 = 6.67333 = 6.67 = 7 3 Significant Figures Exact Numbers(精確數字） Numbers from definitions or numbers of objects are considered to have an infinite number of significant figures The average of three measured lengths; 6.64, 6.68 and 6.70? Because 3 is an exact number 1.8
Rules for Significant Figures in Mathematical Operations • Multiplication and Division: # sig figs in the result equals the number in the least precise measurement used in the calculation. • 6.38 2.0 = • 12.76 13 (2 sig figs)
Rules for Significant Figures in Mathematical Operations • Addition and Subtraction: # sig figs in the result equals the number of decimal(小數點) places in the least precise measurement. • 6.8 + 11.934 = • 18.734 18.7 (3 sig figs)
(1.6)Dimensional Analysis Proper use of “unit factors” leads to proper units in your answer.