Notes from first 3 units of Gen Chem
Notes from first 3 units of Gen Chem Chem 1315-001
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Popular in Chemistry
This 9 page Bundle was uploaded by Mohannad Notetaker on Sunday October 4, 2015. The Bundle belongs to Chem 1315-001 at University of Oklahoma taught by Paul A. Sims in Summer 2015. Since its upload, it has received 22 views. For similar materials see General Chemistry in Chemistry at University of Oklahoma.
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Date Created: 10/04/15
8262015 Chemistry Unit 1 Notes Observamns 1 Observations are also known as data They are the descriptions about the characteristics or behavior of nature 2 Observations often lead to formulating a hypothesis Hypothesis 1 A hypothesis is a tentative interpretation or explanation of the observations 2 A good hypothesis is falsi able Experiments support hypotheses or prove wrong but never correct further experimentation is performed A Scienti c Law 1 A brief statement that summarizes past observations and predicts future ones 2 Allows you to predict future observations Theory 1 Formed by one or more wellestablished hypotheses 2 A scienti c theory is a model for the way nature is and tries to explain not merely what nature does but why 3 Validated by experiments 4 Theories can never be conclusively proven because some new observation or experiment always has the potential to reveal a aw 5 Can be used to predict future observations and it serves as a model for nature Matter 6 Anything that occupies space and has mass 7 Can be classi ed based on state or composition 8 Solid liquid or gas 9 Changes from solid to liquid to gas with increasing temperature 10 Atom and molecule structures lead to different properties Solid matter 1 Atoms packed close together in xed locations 2 Atoms and molecules vibrate but don t move around each other 3 Has xed volume and rigid shape 4 Solid matter may be crystalline in which case its atoms or molecules are in patterns with longrange repeating order 5 Others may be amorphous in which case its atoms or molecules do not have any longrange order 8262015 Liquid matter 1 Atoms and molecules packed closely together but are free to move 2 Have xed volume but not shape Gaseous matter 1 Atoms and molecules have a lot of space in between 2 Free to move 3 Makes them compressible Separating mixtures Homogeneous mixture can be separated by distillation a process in which the mixture is heated to boil off the more volatile easily vaporizable liquid The volatile liquid is then recondensed in a condenser and collected in a separate ask Mixtures are separable because of different physical or chemical properties Decanting carefully pouring off the water into another container sand and water Filtration mixture is poured through lter paper in funnel insoluble solid and liquid Physical changg 1 Changes that only alter state or appearance 2 Atoms and molecules don t change water vaporizing Chemical changg 1 Alter composition of matter 2 Atoms rearrange into different substances rusting iron Different substance 1 Elements combine to form compounds 2 When elements combine an entirely new substance forms De nite production Hydrogen and oxygen mixture can have any ratio of hydrogen to oxygen however a compound formed by the two elements eg Water would have speci c xed ratio of hydrogen to oxygen 8262015 Chemical bonds 1 Compounds are made up of atoms and are held by chemical bonds 2 Atoms rarely exist alone they bond with others to form compounds 3 Two types ionic and covalent Ionic bonds 1 Occurs between metals and nonmetals by transferring electrons 2 When metals interacts with nonmetals electrons are transferred and the metal atom becomes a cation while the nonmetal becomes an anion 3 Electrostatic forces attract the oppositely charged ions to form the ionic bond 4 Creates ionic compounds composed of a lattice or alternating cations and anions Covalent bonds 1 Typically between two or more nonmetals 2 Electrons are SHARED not transferred 3 Atoms bound covalently form a molecule so all covalently bonded compounds are called molecular compounds Representing compounds 1 Use of chemical formulas 2 It represents the elements composing the compound as well as the number of atoms or ions of each of the elements Molecular models 1 More accurate in specifying compounds 2 Ball and stick model to represent atoms and chemical bonds and the arrangement to represent the shape of the molecule 3 Balls are colorcoded to recognize what element is in the compound Units of measurement 1 Standard quantities to specify measurements 2 Very important 3 Most common systems are the metric and English system 4 The SI standard international system is based on the metric system Meter length 1 About 3997 inches 2 100 cm 8262015 Kilogram mass 1 SI unit of mass 2 Mass is a measure of the quantity of the matter within 3 Weight is a measure of the gravitational pull Seconds time 1 Measuring the duration of an event 2 SI unit of time Kelvin temp 1 SI unit of temp 2 Temperature is a measure of the avg kinetic energy of the atoms and molecules that make up the matter 3 Determines the direction of energy transfer heat 4 Thermal energy transfers from hot to cold 5 Kelvin and Celsius degrees are the same size Dimensional analysis 1 Unit equations are statements of two equivalent quantities 2 Need a conversion factor fractional quantity unit converting FROM is on the bottom and the unit converting T0 is on the top 3 Info given conversion factor desired unit Volume 1 How much space occupied by something 2 SI unit is mquot3 3 Lengthwidthheight 4 1mL1cmquot3 Density 1 Dmv 2 Amount of mass per unit volume Sig g 1 Re ect precision 2 Precision depends on the instrument used to make the measurement 3 Greater number of sig g greater precision and certainty of measurement 4 Exact numbers have unlimited precision Rules for rounding 8262015 1 Round down is last digit is 4 or less 2 Round up if last digit is 5 or more 3 Round the nal answer to avoid rounding errors within the problem 4 Last digit determines how to round but it would dropped depending on how many sig gs asked Precision and accuracy 1 Accuracy is how close the measured value is to actual value 2 Precision is how close a number of measurements are to each other how reproducible they are 3 Precise results are consistent with one another 4 Accurate results are close to the actual value Error 1 Random error could be equally high or low 2 Systematic error could either be too high or too low Uncertainty 1 Always include all certain digits plus an uncertain digit when recording measurements to improve precision or accuracy Atoms 1 Comes from atomos Greek for indivisible 2 Example carbon atoms cannot be divided into smaller piece and stay carbon 3 Atoms make up all ordinary matter so you would need to understand how atoms work to understand matter 4 Smallest identi able unit of an element Modern atomic theory 1 Law of conservation of mass matter is neither created or destroyed in a chemical reaction so the total mass of the substance wouldn t change a Law is supports the idea that matter is composed of small indestructible particles 2 Law of de nite proportions all samples of a given compound have the same proportions of their constituent elements despite their source or method of preparation a Also called law of constant composition 8262015 3 Law of multiple proportions when two elements form two different compounds the masses of element B that combine with lg of element A can be expressed as a ratio of small whole numbers a Ratio of the two masses of element B is a whole number Discovery of the electron 1 JJThompson constructed a partially evacuated cathode ray tube a The beam of particles from the negatively charged electrode cathode to the positively charged one anode b Travel in straight lines c Negatively electrically charged d Unaffected by the materials they originated in 2 He measured the chargetomass ratio of the cathode ray particles by de ecting them using electric and magnetic elds 176 x 108 coulombs C per gram 3 Oil drop experiment resulted in the discovery of the charge of an electron whole number multiple of 196 x 10 19 Structure of the atom 1 JJ Thompson proposed the plum pudding model because he believed electrons were small negative particles held in a positively charged sphere 2 Ernest Rutherford conducted the gold foil experiment where alpha particles were directed on to a thin sheet of gold foil a Most particles went through the foil b Some particles were de ected at extreme angles 1 in 20000 c He proposed a new model and concluded that matter contains large areas of empty space but has small regions where the matter is very dense Ernest s nuclear theory 1 Most of the atoms mass and positive charge is contained in the nucleus core 2 Atoms are mostly empty space where negatively charged electrons are dispersed 8262015 3 The amount of electrons is equal to the amount of protons so the atoms have a neutral charge Neutrons 1 Chadwick proposed that some of the atoms mass is from the neutrons neutrally charged particles 2 The mass of it is similar to that of a proton Subatomic particles 1 All atoms contain electrons protons and neutrons 2 Protons and neutrons have similar masses a The mass of the proton is 167262 x 10 27 kg b The mass of the neutron is 167493 x 10 27 kg c The mass of the electron is 91 x 10 31 kg 3 Protons and electrons have identical charges but their signs are different 4 Elements are de ned by the number of protons in the nucleus atomic number Periodic table 1 Each element has a unique symbol and atomic number 2 Arranged in order of increasing atomic number 3 Certain groups of elements had similar properties 4 Divided into two groups a Main group elements elements with predictable properties based on periodic table position b Transition elements elements with lower predictability of properties based on positon on periodic table 5 Periodic law a When elements are listed in increasing mass the similar properties recurred in a pattern 6 Elements are classi ed a Metals b Nonmetals c Metalloids lsotopes 8262015 1 All atoms of a particular element have the same number of protons but not all have the same number of neutrons a Such atoms are known as isotopes 2 The natural abundance is the relative amount of isotopes in a naturally occurring sample of a given element 3 Mass number A atomic number Z number of neutrons lons 1 Charged particles 2 Neutral atoms have an equal amount of electrons and protons 3 Chemical changes cause atoms to lose or gain electrons so they become ions a Cations positively charged b Anions negatively charged Metals 1 Good conductors of heat and electricity 2 Malleable 3 Ductile 4 Shiny often 5 Lose electrons when undergoing chemical changes Nonmetals 1 17 of them 2 Some are solid and others are gases at room temp and bromine Br is liquid at room temp 3 Poor conductors of heat and electricity 4 Not ductile 5 Not maeabe 6 Gain electrons from chemical changes Metalloids 1 Mixed properties 2 Intermediate electrical conductors not all of them Noble gas 1 Alkali Unreactive 8262015 1 Reactive metals Alkali earth metals 1 Fairly reactive Hydrated ionic compounds 1 Ionic compounds containing a speci c number of water molecules associated with each formula unit Molecular compounds 1 Can vary because the elements involved don39t necessarily determine the combination 2 Composed of two or more nonmetals 3 Write the name of the element with the smallest group number rst 4 If in the same group write the one with the greatest row number rst 1 Molecular compounds that release hydrogen ions in water 2 Composed of hydrogen written rst usually Binary acids 1 Hydro pre x 2 Follow with the nonmetal name and change ending to ic Oxyacids 1 Polyatomic ions ending in 39ate change to ic 2 Polyatomic ions ending in 39ite change to ous
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