Chemistry 1210: Week 1 Notes: Ch.1-2
Chemistry 1210: Week 1 Notes: Ch.1-2 Chem 1210
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This 8 page Class Notes was uploaded by Emily Notetaker on Monday August 22, 2016. The Class Notes belongs to Chem 1210 at Ohio State University taught by Dr. Bartoszek-Loza in Summer 2016. Since its upload, it has received 166 views.
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Date Created: 08/22/16
Lecture 1 (Sections 1.1-1.5) Tuesday, August 23, 2016 10:51 PM Matter (1.2 - 1.3) • Matter - occupies space and has mass • Element: cannot be broken down (O, N, Na, Cl) ○ *molecule = 2 and atom = 1* ○ • Substance: definite chemical composition ○ Ionic (salt) ---> NaCl ○ Molecular ----> CH 3H 2H or C H2O6 O ,2and Cl 2 ○ • Phases: solid (s), liquid (l), gas (g), aqueous (aq) • Physical property: observe or measure without changing the identity, color, or boiling point • Chemical property: ability of a substance to change/ react (Fe in air) • Physical Change: Change of phase • Chemical Change: transform into a chemically different substance ○ • Law of constant composition:water mass is always 11% Hydrogen and 89% Oxygen Mixtures • Mixtures are a combination of two or more components in which each component retains its own identity ○ Homogeneous mixture - uniform (lemonade, air, chocolate milk) ○ Heterogeneous mixture - non-uniform (bacon, granite) • Separation: filter/evaporate, distill Measurement (1.4) • Intensive Properties ○ Properties that do not change when the amount changes ○ Melting point of ice, density • Extensive Properties ○ Properties that change when the amount of a substance changes ○ Energy produced burning gasoline • A measured quantity has both a number and a unit • Prefix ---> km - m - dm - cm - mm - um - nm Chapter 1 Page 1 • Prefix ---> km - m - dm - cm - mm - um - nm Measurement Uncertainty (1.5) • Exact numbers ○ 1 dozen = 12 eggs • Inexact numbers ○ Measured - 3.45 g, 25.77 mL Last digit is uncertain (2.5 +/- 0.1 cm) • Precision ○ How closely individual measurements agree with eachother You do not hit the bullseye, but you hit the same spot 3 times • Accuracy ○ How closely individual measurements agree with the "true" You hit the bullseye once, but the other two arrows are around the target • Data and Error Analysis ○ Determinate error: Read top vs. bottom of meniscus throughout experiment ○ Indeterminate error: Estimate the last digit • Significant Figures ○ Multiplying/dividing Always take the least number of significant figures ○ Adding/Subtracting Always take the least amount of decimal places Dimensional Analysis (1.6) Chapter 1 Page 2 Section 1.6 Overview Wednesday, August 24, 2016 10:12 AM Dimensional Analysis(Pg. 27 -31) • In dimensional analysis units are multiplied together or divided into each other along with the numerical values. Equivalent units cancel each other out. ○ Conversion factor - a fraction whose numeratorand denominator are the same quantity expressed in different units. " Given unit x • It is often necessary to use several conversionfactors to solve a problem ○ Number of inches = Quiz 1 Info Thursday, August 25, 2016 2:33 PM The quiz will be on chapter 1, the notes, and the homework. Sections 2.1 - 2.4 Overview Wednesday, August 24, 2016 10:35 AM Chapter 2 : Atoms, Molecules, and Ions 2.1 | The Atomic Theory of Matter • Early greek philosophers like Democritus believed that the material world was made up of tine indivisible particles called "atomos" • Later Plato and Aristotle stated that these particles were not possible • John Dalton eventually formulated the notion off atoms that he used to measure amounts of atoms when they reacted with other substances ○ Dalton's Atomic Theory 1. Each element is composed of extremely small particles called atoms. 2. All atoms of a given element are identical, but the atoms of one element are different from the atoms of all other elements. 3. Atoms of one element cannot be changed into atoms of a different element by chemical reactions; atoms are neither created nordestroyed in chemical reactions. 4. Compounds are formed when atoms of more than one element combine; a given compound always has the same relative number and kind of atoms. 2.2 | The Discoveryof Atomic Structure • The atoms is composed of subatomic particles : electrons, neutrons, and protons. ○ Cathode Rays and Electrons: Electrical discharge through a glass tube, pumped empty air . When a high voltage was applied to electrodes in tube, radiation was produced between electrodes. This radiation is called cathode rays - where they originated at the negative electrode and traveled to the positive electrode More experiments under J. J. Thomson showed that the cathode rays were deflected by magnetic or electric fields in a way that was consistent with a negative electrical charge. □ Described the cathode rays as streams of negatively charged particles. □ Led to the discovery of the electron. And then the charge - to - mass ratio 1.76 C/g □ ○ Oil Drop Experiment: Robert Milikan was able to measure the charge of an electron by allowing drops of oil to fall between electrically charged plates. Milikan changed the voltage between the plates, and measured how that affected the rate of the fall. He found the value of the charge to be 1.602 x C This allowed for the electron mass to be found from the value of the charge and Thomson's ratio □ * g ○ Radioactivity: Henri Becquerel discovered that uranium spontaneously emits high - energy radiation or is radioactive. Ernest Rutherford then found there were three types of radiation: □ Beta - attracted to positively positively charged plate - fast moving particles □ Gamma - high energy radiation and does not carry a charge (x-rays) □ Alpha - positive charge that are attracted to negative plate - fast moving particles Chapter 2 Page 5 ○ The Nuclear Model of the Atom: Plum pudding model □ Thomson said the atom consists of a uniform positive sphere of matter where the mass is evenly distributed and the electrons are embedded like seeds. Nuclear Model: □ Rutherford observed in an experiment at which angles alpha particles were being deflected as they passed through gold foil. Almost all of the particles passed through, but went on to observe scattering at large angles which disproved the plum pudding model. The alpha particles were being deflected by a positive center (the nucleus). □ The model explained most of the mass of each atom and its positive charge reside in a small, dense region called the nucleus. And that most of the atom was empty space with electrons. □ Protons were discovered by Rutherford and neutrons were discovered by James Chadwick. 2.3 | The Modern View of the Atomic Structure • In modern times, the charge of the electron is expressed as -1 and a proton is expressed by +1. Neutrons are electrically neutral. • *Every atoms has an equal number of electrons and protons* • Protons and neutrons are in the nucleus of the atom. • Electrons are attracted to the protons in the nucleus by an electrostatic force. • Atomic Numbers: ○ The number of protons in an atom. ○ *The atoms of each element have a characteristic # of protons* • Mass number: ○ The amount of neutrons plus the protons. ○ Atoms can differ in the amount of neutrons and consequently in mass too. • Isotopes: ○ Atoms with identical atomic # but different mass #, because of different # of neutrons in nucleus. 2.4 | Atomic Weights • Measured in atomic mass units (amu) • Elements mostly occur as mixtures of isotopes so we can determine the average atomic mass or atomic weight of each element. Chapter 2 Page 6 Lecture #2 Thursday, August 25, 2016 2:22 PM Atomic Theory of Matter (2.1) • 400 BC: Matter consisted of very small indivisible particles, atomos. • 1800s(Dalton's hypothesis) - 2000 year gap ○ Law of multiple proportions: CO, CO 2 Mass of A that combines with the mass of B is a ratio of small whole numbers. AB, A B, AB 2 2 ○ Law of constant composition:H O 2 Proust (1799) - took different samples of the same substance contain the same proportion of atoms □ Water is always 11% H, and 88% O ○ Law of conservationof mass: Lavosier(1785) - During a chemical reaction, the total mass before the reaction is equal to the total mass after the reaction Discoveryof Atomic Structure (2.2) 1850s:atoms composedof charged particles • Thompson:charge to mass ratio (C/g) • Milikin: charge of an electron e mass = 9.10 *10 -28g • Rutherford : alpha, beta, and gamma rays • The Nuclear Model of the Atom ○ Thompson:plum pudding ○ Rutherford: electron scattering ○ Chadwick: neutron Atomic Structure - Modern View (2.3) • Can see spider web thread: 0.0001cm • Atom: 10 -10m Nucleus: 10 -14m
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