Matter, Scientific Method, and Atoms
Matter, Scientific Method, and Atoms CHEM 111 (Section 64)
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This 5 page Class Notes was uploaded by Jaymi Notetaker on Sunday September 6, 2015. The Class Notes belongs to CHEM 111 (Section 64) at Ball State University taught by Christofield, Zubkov in Summer 2015. Since its upload, it has received 63 views. For similar materials see General Chemistry 1 in Chemistry at Ball State University.
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Date Created: 09/06/15
CHEM 111 week 2 August 31 2015 The States of Matter Solid rigid incompressible has a definite shape and volume Liquid uid incompressible no definite shape but volume remains the same Gas uid compressible no definite shape or volume Conversion Factors 1kg1000g 1000 mm1m 1000mg1g 100cm1m 1000mL1L 1mL1cm3 Metric to American Conversions Quantity Metric Unit American Unit Mass 454 gram 1 pound 16 ounces Length 1 meter 394 inches 328 feet 254 centimeters 1 inch 1 kilometer 0621 miles Volume 1 liter 106 quarts 379 liters 1 gallon The States of Matter continued Water H20 0 H H as a gas water vapor steam compressible molecules are far apart moving randomly as a solid ice not separate positioned in rows vibrating but not randomly moving Physical Change a change in the form of matter but not in its identity Ex Ice melting alcohol evaporating Chemical Change a change in the identity of matter Ex hydrogen burning in the air to make water digestion of food Physical Properties can be observed and measured without changing the composition and identity of matter Ex melting point magnetism Chemical Properties can be observed only when changing the composition and identity of matter Ex ammability erosion Classifications of Matter Pure Substance a form of matter that has a definite composition and distinct properties Element a pure substance that cannot be separated into simpler substances by chemical means also only one type of atom Compound substance composed of atoms of two or more elements chemically united in a fixed state Mixture a combination of 2 or more substances each retaining its own identity every one is unique depends on substances Homogeneous Mixture uniform in its properties throughout the sample Heterogeneous Mixture consists of distinct parts each with different properties The Scientific Method A systematic approach to research Experiment ultimate judgment of ideas careful observation of natural phenomena carried out in a controlled manner so that the results can be duplicated and rational conclusions obtained Result end product of an experiment that can be concisely stated in the form of a natural Law can be qualitative not a number or quantitative numbers Hypothesis tentative explanation of the results needs to be tested further upon Theory Thoroughly tested explanation of the phenomena it is a hypothesis that has survived multiple experiments Law a concise statement or mathematical equation about a fundamental relationship Laws amp Theories amp Experiments Law of the Conservation of Mass Lavoisier The total mass remains the same during a chemical reaction Matter can neither be created nor destroyed Dalton s Atomic Theory Elements are made up of tiny indivisible particles called atoms All atoms of the same element are identical to each other but other atoms of different elements are not identical to a different element s atom Compounds are composed of o Atoms of two or more elements 0 Chemically combined 0 In fixed proportions A chemical reaction changes only the attachments between atoms in molecules No atoms are destroyed Based upon Law of Definite Proportions Ioseph Proust 1799 Any compound is always made up of elements tin the same proportion by mass Law of Multiple Proportions Two elements can combine to form different compounds The masses of one element that combined with a fixed mass of the other element are in ratios of small whole numbers Thomson s Cathode Rays Experiments 1897 Showed that electrons are constituents of all matter What was Thomson able to calculate about the electron o MasstoCharge Ratio Millikan s Experiment Oil droplets and positive and negative plates experiment Found smallest charge of atom was the electron Enabled the calculation of the mass of the electron Thomson 1904 Plumpuddingquot model of the atom Rutherford 1910 In experiment gold foil was bombarded by positively charged Aparticles Randomly scattered atoms Planetary Model of Atom around for 20 years then replaced by new model Figure 29 page 48 referred to during lecture Atoms are mostly empty space Inside the Atom Particle Mass g Mass amu Charge Location Proton P 167262gtlt103921 1 1 Nucleus Neutron N0 167493x103924 1 O Nucleus Electron 910939x 10 3928 L 1 Outside of 1837 nucleus Atomic Number Z Number of protons in an atom Examples Hydrogen 1 proton Carbon 6 protons Sodium 11 protons Mass Number A The total number of protons and neutrons within any atom Example 5 protons 5 neutrons 5 electrons 11 is Mass number don t count the electrons A2 9 Mass number on top atomic number on bottom Neutrons Mass Number protons Electrons Protons if atom is neutral Isotopes amp Nuclide Symbols Isotopes atoms that have the same atomic number but different mass numbers same element 126C 9 6 protons 6 neutrons 136C 9 6 protons 7 neutrons SAME ELEMENT 13C is just a little heavier than 12C Note these are 2 Carbon Isotopes Periodic Table a chart in which elements having similar chemical and physical properties are grouped together 7 Atomic Number N Element Symbol 140067 Mass Atomic Mass mass of atom in atomic mass units amu 1 amu 112th of the mass of a carbon12 atom 166054 gtlt 103924g The mass of one Carbon12 atom is exactly 12 amu The only mass whose mass is whole numbers Average Atomic Mass weighted average of the masses of the naturally occurring isotopes of an element sometimes called atomic weight Average Atomic Mass 2 atomic mass gtlt fractional abundance note above equation must add numbers from all isotopes Will see next page Example 2 Example 1 A class full of 100 students and 1 professor where ages are in between 18 and 44 Average age Closer to 18 because the main population students pulls it towards 18 Example 2 Chlorine Two naturally occurring isotopes Find Average Atomic Mass 35CI 9 34969 amu 9 7553 abundance 37C1 9 36966 amu 9 2447 abundance Average Atomic Mass 2 atomic mass x fractional abundance Chlorine s Average Atomic Mass 35CI mass x 35CI fractional abundance 37CI mass x37CI fractional abundance 7553 2447 34969 amu x TOO0 36966 amu x TOO0 34969 amu x 7553 36966 amu x 2447 3546 9 this is the number that is listed on the periodic table Molecules Molecule a group of atoms in a definite arrangement tightly held together by attractive forces Diatomic Molecule H2 N2 O2 Polyatomic Molecule HOH H2O Molecular Formulas Molecular Formula H2 Structural Formula HH Molecular Formula shows the exact number of different atoms in a molecule Empirical Formula shows the smallest whole number ratio of atoms present in molecule Example Glucose Molecular C6H1206 Empirical CH2O 9 all are divisible by 6
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