lecture%201 - One must know and understand, at least in...

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Unformatted text preview: One must know and understand, at least in part, scientific language and the scientific approach to problem solving. One of the most confusing things is the special way scientists use ordinary words and, to complicate matters, they even invent new words The scientist's approach must be clearly understood. It is different, neither strange or esoteric. From a scientist's point of view there actions are quite logical and they question why everyone doesn't see things that way. Science and Common Sense Whitehead in 1911 points out that common sense is a poor master "Its sole criterion for judgment is that the new ideas will look like the old ones." How are common sense and science alike and how are they different? Alike: Science is a systematic and controlled extension of common sense. James Bryant Conant in 1951 states that common sense is a series of concepts and conceptual schemes satisfactory for the practical use of humanity. There is however a key flaw in this approach In 1800, is was common sense to use punishment as a basic tool of learning. By mid 1900s, reward appears to be more effective than punishment Science is different from common sense Science uses conceptual schemes and theoretical structures Science systematically and empirically tests theories and hypothesis Science attempts to control extraneous causes Science pursues relations consciously and systematically Science rules out metaphysical (untestable) explanations Peirce's Four Methods of Knowing Method of tenacity influenced by established past beliefs Method of Authority influenced by the weight of tradition or public sanction A priori method (Intuition) natural inclination toward the truth Method of Science selfcorrecting, notions are testable and objective What is Science? Static view science is an activity that contributes to systematized information to the world Heuristic view Serves as abase for further scientific theory and research Heuristic serving to discover or reveal What is the function of Science? A discipline or activity aimed at improving things To establish general laws covering the behaviors of empirical events or objects with which the science in question is concerned and thereby enables us to connect together our knowledge of the separately known events, and to make reliable predictions of events as yet unknown Aims of science develop theory and explain natural phenomena Promote understanding and develop prediction A theory is a set of interrelated constructs (concepts) definitions, and propositions that present a systematic view of phenomena by specifying relations among variables, with the purpose of explaining and predicting phenomena Theory A set of propositions consisting of defined and interrelated constructs Sets out the interrelations among a set of variables (constructs) and in doing so, presents a systematic view of the phenomena described by the variables Explains phenomena and allows predictions Good theories cannot fit all observations Blondlot claims all matters emits Nrays Almost 100 papers are published on Nrays Specialized equipment is developed If you didn't see them you eyes aren't sensitive enough or you didn't set the equipment up right Schwartz claims ulcers are due to stomach acid All research becomes dedicated to reducing or neutralizing stomach acid In 1985 Warren and Marshall discovered that the helioc bacter pylori cause ulcers. Now antibiotics clear up ulcers effectively and inexpensively. It took 75 years!!! Scientific Research Systematic Controlled Empirical Amoral Critical Investigation of Natural Phenomena The Scientific Approach Problem Obstacle Idea Hypothesis Reasoning Deduction Observation Test Experiment Problem Obstacle Idea Formulate the research problem or questions to be solved Hypothesis Formulate a conjectural statement about the relationship between phenomena and variables Reasoning Deduction Scientist deduces the consequences of the hypothesis. This can lead to a more significant problem and provide ideas on how the hypothesis can be tested in observable terms Observation Test Experiment This is the data collection and analysis phase. The results of the research conducted are then related back to the problem Is it Science? Different Forms of Matter: Solid (s) Liquid (l) Gas (g) Properties of Matter Physical: something you can observe without changing the identity Intensive: Does NOT depend on the size of the sample (temperature, density) Extensive: Does depend on the size of the sample (mass, volume) Chemical: the ability of a substance (or mixture) to change Base Units (SI) length = meter (m) mass = kilogram (kg) time = second (s) electric current = ampere (A) temperature = Kelvin (K) chemical amount = mole (mol) luminous intensity = candela (cd) *Prefixes for these are found Appendix 1, know Mega, kilo, centi, milli, micro, nano and pico KNOW THESE base units and prefixes! Derived Units When fundamental Units are combined together to express and more complicated property than the fundamental units. For example: density = mass/volume kg/m3 , both mass and volume or extensive properties but their ratio, the density is an intensive property. Force SI unit = Newton (N) = (kg)(m)/s2 A force applied to an object changes its state of motion. e.g. A force is necessary to cause acceleration of an initially stationary object. F = (m)(a) = (mass)(acceleration) gravitational force = (mass)(9.8 m/s2) electrostatic (Coulombic) force = kq1q2 /r2 Force Energy SI unit = joule (J) = (Newton)(m) = (kg)(m2)/s2 Three possible forms: Kinetic: EK = mv2 Potential: Due to gravitational field: EP = mgh g = acceleration of gravity (9.8 m/s2 on Earth) h = height to which object has been raised Due to attraction/repulsion of electrical charges: EP = q1q2 /4 0 r q1 and q2 = charge on each object in C (Coulombs). (For an electron, q = 1.6 x 10-19 C.) r = distance between objects 0 = vacuum permittivity = 8.854 x 10-12 (J-1)(C2)(m-1) (See next section regarding force. In this case F = kq1q2 /r2) Coulomb Potential Energy The potential energy of two oppositely charged particles decreases as they get closer together. Electromagnetic (EM) energy: The energy of EM radiation. The electric and magnetic waves are perpendicular to one another and to the direction of wave propagation. All EM radiation travels at the speed of light (c). E = h = frequency in s1 (Hertz) h = Planck's constant = 6.6 x 1034(J)(s) Total Energy of a Particle and Conservation of Energy Total energy: E = EK + EP Kinetic energy can be converted to potential energy and vice versa. In chemical reactions energy is not created or destroyed. Nuclear Reactions In fission or fusion, mass is converted to energy: E = mc2 Energy Physical Properties are those that do not involve changing the identity of a substance. Chemical Properties are those involving changing the identity of a substance. Extensive properties are those that depend on the mass of the sample; intensive properties are those that are independent of the mass of the sample. The precision of a measurement is determined by the reproducibility, whereas the accuracy is how close a measurement is to the true or accepted value. Atomic Theory Greek Philosopher Democretus first discussed the concept of the atom indivisible Dalton's Atomic Hypothesis All atoms of a given element are identical The atoms of different elements have different masses A compound is a specific combination of atoms of more than one element In a chemical reaction, atoms are neither created nor destroyed, they exchange partners to create new substances. B. Elements & Atoms The Nuclear Model Thomson: Canal Rays Used cathode rays to show that some subatomic particles (electrons) have negative charge (-e). Determined the charge/mass ratio: e/me. Millikan: Oil Drop Experiment Used electrical force on charged oil drops to measure e. Calculated me from Thomson's ratio. e = 1.6 x 10-19 C me = 9.1 x 10-31 kg Discovery of the electron: J.J. Thomson J.J. Thomson "Could anything at first sight seem more impractical than a body which is so small that its mass is an insignificant fraction of the mass of an atom of hydrogen? which itself is so small that a crowd of these atoms equal in number to the population of the whole world would be too small to have been detected by any means then known to science. "http://www.aip.org/history/electron/jjsound.htm Recording made in 1934. From the soundtrack of the film, Atomic Physics copyright J. Arthur Rank Organization, Ltd., 1948. Rutherford Demonstrated that atoms are not of uniform density. Most of the mass is in the center (nucleus). The remainder is a much lower density "electron cloud". The majority of the particles (He nuclei) projected at a piece of platinum foil passed through but some were deflected. He concluded that particles were only deflected if they collided with the platinum nuclei but were not affected by the electrons that have a much lower mass. symbol charge mass (kg) electron e-1 9.1 x 10-31 proton p +1 1.7 x 10-27 neutron n 0 1.7 x 10-27 Rutherford's Experiment Nuclear Model of the Atom Atomic View of Matter All matter is made up of various combinations of simple forms of matter called the chemical elements. An element is a substance that consists of one kind of atom. Atomic Number In a neutral atom: # protons = # electrons. Atomic # (Z) = # protons Neutrons & Isotopes Mass spectrometry has shown that not all atoms of a particular element have the same mass. Since the # of protons does not vary for atoms of an element and the mass of the electron is insignificant relative to the proton mass, another type of nuclear particle is implied. Mass Number (A) = (# protons) + (# neutrons) (Whole #, no fractions. Does not have units.) Atomic Mass (matom) is the mass of a single atom (in grams). Atomic Weight (M) is the mass of one mole of atoms (in grams). Periodic table: atomic weight is located in the bottom of each square. Isotopes: Atoms with the same # of protons but varying # of neutrons. Not much variation in chemical properties of isotopes of a particular element because these properties are determined by the # of protons and electrons. Chemical symbols for isotopes: Atomic mass indicated as a superscript 1H 3H 12 C 13 C Applications: 3 H: radioactive. Used for tracking biological molecules in vivo. 13 C: Slight variations in abundance used to determine if samples obtained from minerals are of biological origin, i.e. fossils. B.5 Organization of the Elements Periodic Table - three levels of organization: Periods: rows defined by the highest energy level containing electrons; i.e. principal quantum #s1-7. Groups: columns defined by # of valence electrons and reactive properties; i.e. tendency to lose or gain electrons when forming bonds. Two labeling systems: IA IIA IIIB IVB VB VIB VIIB VIIIB IB IIB IIIA IVA VA VIA VIIA VIIIA 1 2 3 4 5 6 7 8-10 11 12 13 14 15 16 17 18 Blocks: sections defined by the type of orbitals containing the highest energy electrons; i.e. s, p, d or f. Other Subsections of the Periodic Table Main Group Elements: groups IA, IIA, IIIA-VIIIA 1 2 13 - 18 Metals: groups IA, IIA (s block) and some of IIIA-VA. Transition Metals: groups IIIB-VIIIB, IB-IIB (d block). Inner Transition Metals: f block Metalloids: some of groups IIIA-VIA. Nonmetals: all of groups VIIA-VIIIA, some of IVA-VIA. Hydrogen: often placed in group IA but not a metal. Correlation of Element Physical and Chemical Properties with Position in Periodic Table Metals Physical: Malleable, ductile, conduct electricty, have luster. Chemical: Form ionic bonds with non-metals by donating electrons Non-metals: Physical: Brittle, do not conduct electricity, no luster. Chemical: Form ionic bonds with metals by accepting electrons. Form covalent bonds with other nonmetals by sharing electrons Metalloids: Physical: Similar to metals. Chemical: Similar to non-metals. Examples of Element Physical and Chemical Properties Metal aluminum (Al): ionic compound with non-metal: AlCl3 Non-metal carbon (C): graphite, coal. Covalent compound with other non-metal: CH4 (methane). chlorine (Cl): Ionic compound with metal shown above. Metalloid silicon (Si): Conducts elec. Forms covalent bonds with the non-metal O, e.g. SiO2 found in minerals Transition Metals (d block) e.g. Fe, Ni, Cu, Ag (silver), Au (gold) More reactive than metals in the p block but less reactive than metals in the s block (group IA and IIA). (Do not release electrons as easily as do s block metals.) Inner Transition Metals (f block) Lanthanides Actinides: most isotopes are radioactive [e.g. uranium (238U), plutonium (244Pu)] Subclassification of Nonmetals Noble gases (group VIIIA): Much less reactive than any of the other elements. Elemental form is monatomic. All are gases at room temp. Halogens (group VIIA): Elemental form is diatomic. e.g. F2 and Cl2 (gas at room temp) Br2 (liquid at room temp) I2 (solid at room temp) Periodic Table The periodic table is an arrangement of the elements that reflects their family relationships; members of the same group typically show a smooth trend in properties Know the major subdivisions of the periodic table and the names of important groups. What numbers are significant? All nonzero numbers are significant 2. Zeros to the left of the number are NOT significant called place holders 3. Imbedded zeros in the number are significant 4. If a zero is to the right of a decimal point and after a number it is significant 5. If the number does NOT contain a decimal point then the zero to the right is NOT significant See Appendix 1C for scientific notation and Sig Figs 1. Homework Memorize the first 38 elements names and symbols. Memorize the SI units and prefixes discussed today Memorize tables D1 D4, we will use these later! Section A Section B Counting Atoms Chemistry is a quantitative science--we need a "counting unit." MOLE 1 mole is the amount of substance that contains as many particles (atoms, molecules) as there are in 12.0 g of 12C. Particles in a Mole Avogadro's Number Amadeo Avogadro 1776-1856 NA = 6.0221 x 1023/mol *There is Avogadro's number of particles in a mole of any substance. ...
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This note was uploaded on 10/06/2008 for the course CHEM 234234234 taught by Professor Johnson during the Fall '08 term at UCSD.

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