chapter1 chemistry 121

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Chemistry 121 Dr Patrick Woodward Office Office E-mail → 3109 Newman and Wolfrom Lab Hours → 2:30-3:30 M, T, W, R → woodward@chemistry.ohio-state.edu Phone → 688-8274 Web Site → www.chemistry.ohio-state.edu/~woodward/chem_121.htm Chemistry 121 Required Materials Text → “Chemistry, The Central Science” by Brown, Lemay and Bursten 9th Edition Lab Manual → “General Chemistry Laboratory Experiments, Volume 1” by Casey & Tatz Lab Notebook → “Student Laboratory Notebook” Calculator → TI-30, Sharp EL-509, Sharp EL-531, Casio FX-250 www.chemistry.ohio-state.edu/~woodward/chem_121.htm Grading Scheme Midterm (Tues, Feb 3rd) Midterm (Tues, Feb 24th) Final Exam (Tues, Mar 16th) Laboratory (10 labs) Quizzes (6 Quizzes, drop the lowest) Total 1000 175 175 300 200 150 pts pts pts pts pts pts Opportunities to problems  Take home quizzes  Recitation Exercises  Homework Problems (at the end of the chapter)  Web Material (Old exams, sample quizzes, CD exercises) Top Myths about Chem 121 This class is a weed out class For example consider the final grade distribution from Autumn 2002 (beginning with ~300 students): 21 Dropped 20 Failed 29 D/D+ 126 C-/C/C+ 59 B-/B/B+ 46 A-/A Top Myths about Chem 121 It’s OK to blow off lab, because it’s only 20% of your grade If you don’t get 50% in lab, you will be given a failing grade Extra time will not be given to make up missed labs Top Myths about Chem 121 The curve will save me If you get below 600 points (60%) the best grade you can hope for is C-, and your likely to get a D or D+ If you get below 500 points (50%) you’re almost certain to fail the class Top Myths about Chem 121 There are so many students that office hours will be very crowded, plus professors don’t want to be bothered Office hours are usually only crowded before the exams I set aside time to see you during office hours so it’s boring when no one comes I’m also happy to make appointments for other times if you have conflicts with my office hours Top Myths about Chem 121 Knowledge of chemistry will make you more attractive to the opposite sex and enhance your love life Unfortunately based on personal experience I see no evidence for this kind of cause and effect relationship Scientific Method Keep in mind though that generally hypotheses and even theories are based on an incomplete set of experiments, so that later experiments or advances may provide further information that shows the theory or hypothesis to be incorrect Classification & Properties of Matter Matter – Anything that has mass and occupies space Atom – The smallest stable building block of matter Made up of protons, neutrons & electrons Molecule – Groups of atoms held together with a specific connectivity and shape Composition tells us the types of atoms that are present in a compound and the ratio of these atoms (for example H2O, C2H6O, etc.) Structure tells us which atoms are connected (bonded) to each other, how far apart they are, and the shape of the molecule Elements, Compounds & Mixtures Pure Substance → Matter that has a fixed composition and distinct properties All substances are either elements or compounds Elements → All atoms are the same, i.e Oxygen (O2), Gold (Au), Silicon (Si) and Diamond (C) You should memorize the elemental symbols in Table 1.2 Compounds → Contains more than one type of atom, but all molecules (or repeat units) are the same, i.e Water (H2O), Ethanol (C2H6O), Quartz (SiO2), Sodium Chloride (NaCl) All compounds follow the law of constant composition Mixture → Have variable composition and can be separated into component parts by physical methods Mixtures contain more than one kind of molecule, and their properties depend on the relative amount of each component present in the mixture Periodic Table Ne SO3 N2 Homogeneous Mixture Homogeneous & Heterogeneous Mixtures Homogeneous Mixture → Composition and properties are uniform Sometimes called a solution Air – principle components include O2, N2 & CO2 Vodka – principle components are ethanol and water Brass – solid solution of Cu and Zn Ruby – solid solution of Al2O3 and Cr2O3 Heterogeneous Mixture → Composition and properties are non-uniform Chocolate Chip Cookie – Chocolate, Dough, etc Concrete – Cement, Rocks, etc Vomit – Depends upon previous intake of food and drink Chemical and Physical Properties Physical Properties → The identifying characteristics of matter Some properties can be readily measured with our senses, such as odor and color, instruments are needed to measure other properties, such as electrical resistivity, compressibility, hardness, melting point, etc Chemical Properties → Describe the reactivity of a substance toward other substances Examples include: Ethanol burns in air (reacts with oxygen in the air) Sodium reacts vigorously with water, Corrosion of metal parts (rust), Trinitrotoluene (TNT) is explosive, Lysergic acid diethylamide (LSD) is a hallucinogenic drug Ethanol Stoichiometry = C2H6O Melting Point = -115 ºC Boiling Point = 78 ºC Density = 0.79 g/cm3 Chemical Prop = Intoxicating Dimethyl Ether Stoichiometry = C2H6O Melting Point = -140 ºC Boiling Point = -24 ºC Density = Gas Chemical Prop = Intermediate Ethylene Glycol Stoichiometry = C2H6O2 Melting Point = -16 ºC Boiling Point = 197 ºC Density = 1.11 g/cm3 Chemical Prop = Toxic SI (Metric) Units Metric Prefixes You will be expected to know these prefixes from memory Significant Figures Non-zero numbers are always significant Zeros between non-zero numbers are always significant Zeros before the first non-zero digit are not significant (Example: 0.0003 has one significant figure.) Zeros at the end of the number after a decimal place are significant Zeros at the end of a number before a decimal place are ambiguous (e.g 10,300 g) Significant Figures & Calculations Addition and Subtraction Line up the numbers at the decimal point and the answer cannot have more decimal places than the measurement with the fewest number of decimal places Multiplication and Division The answer cannot have more significant figures than the measurement with the fewest number of significant figures Precision and Accuracy Units of Volume m3 × (1003 cm3)/(1 m3) = 1,000,000 cm3 1,000,000 cm3 = × 106 cm3 Periodic Table Chemical Reactivity 2H2(g) + O2(g) → 2H2O(g)
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