Chemisty Chapter 1 Notes I Scientific method Steps of The Method 1 2 3 4 Observation Formulation of Hypothesis Prediction Testing Law vs Theory o Law Summarizes many observations o Theory Provides an explaination for laws cannot be proven Molecular Perspective o Chemists are interested in the dtructure of matter at the particulate level o Matter is the physical materials found in our environment consists of atoms and molecules II Birth of Modern Chemistry Lavoisier Debunks Phlogistron Theory o Phlogiston Theory Originally it was believed materials that burn contain phlogiston and burning it left a residue o Lavoisier realized this was false when he discovered the Law of Conservation Mass o Lavoisier is considered Father of Modern Chemistry Founder of Law of Conservation First to classify elements and compounds Element vs Compound o Element Pure substance unbreakable o Compound Pure substance that can be broken into small subunits Law of Conservation of Mass o Mass is never created or destroyed Law of Definite Proportions o Elements in a compound are always in a constant porportion Law of Multiple Proportions o When two elements can combine and make multiple compounds the ratios are represented by two whole numbers III Atomic Theory John Dalton 1804 o Discovered that elements are composed of atoms Found that they are unchangeable and never dissappear o Molecules refer to either elements of compounds Atoms can combine to form compounds Mass is very important it s the cornerstone of modern chemistry IV Atoms Molecules Joespeh Gay Lussac 1808 o Discovered the Law of Combining Values Volumes of reaction gases are in simple whole number ratios Law of Combining Volumes o H2O experiment He found that 2H 1O H2O Amadeo Avagadro 1811 o Avagadro s Law Equal columes of gas at controlled pressure and temp contain an equal number of molecules Figured out that even though oxygen is an element it is mostly availible as O2 because it is diatomic The Diatomic Elements o Atoms that are primarily availible diatomically H2 N2 O2 F2 Cl2 Br2 I2 Class Discussion o Atoms consist of protons neutrons and electrons Electrons orbit around the nucleus If the number of protons is equal to the number of electrons the element is a normal atom If it loses or gains electrons it is an ion o Atoms are measured 1A 1 10 10 m Roughly 1 5 Angstroms o Atomic Composition Each unit has different weights V Mole Molar Mass Mass o Masses on periodic table are based around carbon Each one was assigned it s number based on C Isotopes have varying mass numbers but always have the same atomic number Moles o Number of atoms or molecules present in a sample when the mass is equal to it s molecular mass o Mole Number of atoms is the relative mass of it s molecules Calculating Nucleons o Subrtact atomic number from the mass number to find nuetron number Molar Mass o AMU Atomic mass units o Avagadro s Number NA 6 022 1023 Mass to Mole Coversions o Conversion Factors The appropriate factor that you need to multiply the given quantity by Stoichiomentric Factor o Also known as the conversion factor o Limiting Reactant the reactant of which we have the least VI Energy Kinetic Energy o The energy of a substance is the the sum of its kinetic energy and its potential energy o Kinetic Energy Energy of motion More On Energy o Potential Energy Energy due to position Potential energy in dynamite is a result of the relative positions of the atoms in the molecules o Energy equation KE 1 2mv2 o E final energy initial energy Ef Ei Systems in Nature seek position of lowest energy VII Electromaagnetism Coloumb s Law Electromagnetic Force o Force of interaction between cahrged particled when they re brought close to one another Coloumb s Law o Two particles of charge q1 and q2 separated by distance r experience a force F o Coulomb s Constant k 8 9875 109 F kq1q2 r2 Equation of Force is the dielectric constant q1 and q2 are the charges in Coulomb s 1 in a vaccum but 79 in water When F is negative the force is attractive When F is positive the force is repulsive o Opposite charges attract Like forces repel Class Discussion o As ion charge increases the attractive force increases o As the distance increases attractive force decreases o Electrostatic Forces Divalent anions with divalent cations has 4x the energy and 2 monovalent ions Charge on the ions themselves depends on physical properties Energy Equations o Energy is defined as a force exerted through a distance E F r o Change in potential energy can be found by multiplying equation of force by r to get the Energy of interaction E kq1q2 r VIII Atomic Structure JJ Thompson 1897 o Cathode Ray Rays were deflected by electric and magnetic rays Found the charge to mass ratios Cathode rays are particles He discovered there were negatively charged particles First to discover electrons Robert Millikan 1909 o Electron Charge Used an oil drum and found the terminal speed of oil droplets adjusted voltage until it was suspended mid air Using the electrostatic and gravitational forces he was able to determine the charge The charges all corresponded to 1 6 10 19 Rutherford 1911 o Gold Foil Experiment Observed 1 in 20 000 particles were deflected and determined the existence of the nucleus Found it to be 1 20 000 the size of the atom IX Subatomic Particles Atomic Number o The number of protons in the nucleus Z Mass Number o The sum of the number of protons and the number of neutrons A o Molecular Weight sum of atomic weights of all atoms in a molecule X Isotopes Ions Isotopes o Different form of the same element Same atomic number different mass The behave differently as shown o Isotopes in existance are averaged to give us the mass number on the periodic table Charge o It s not continuous it comes in bundles of 1 6 10 19 C Charge of particle of protons of electrons o Atoms have no charge if they lose or gain electrons they become ions Ions o Cations Produced when electrons are lost o Anions Produced when electrons are gained Metals tend to lose electrons Non metals tend to gain electrons Noble gases don t form ions at all XI Mendeleev Periodic Law Mendeleev o The Periodic Table He arrange elements in order of their atomic masses Columns form families or groups Rows form periods Left holes in his chart so that elements with corresponding atomic numbers could be discovered Metals o Lustrous solids malleable ductile heat eletricity conductors Nonmetals o Gases or dull brittle solids poor conductors Metalloids o Have