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# Chapters 1-3 Book Notes Chem 141

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This 9 page Class Notes was uploaded by Cassidy Zirko on Friday September 4, 2015. The Class Notes belongs to Chem 141 at University of Montana taught by Mark Cracolice (P) in Fall 2015. Since its upload, it has received 321 views. For similar materials see College Chemistry 1 in Chemistry at University of Montana.

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Date Created: 09/04/15

Chem 141 Prof Cracolice Lesson 1 How Do Scientists Use Algebra to Reason and Calculate Book Notes 83115 11 How is Algebra used to Reason in the Sciences Algebra thought of as arithmetic in which letter are used to represent variables Variables quantities that may have different values can appear in equations Equation represents a mathematical relationship among the variables Direct proportionalities 0 Two variable quantities are related in such a way that when one is manipulated by a constant so is the other I I Traveling at a constant speed in car the distance traveled is directly proportional to the time it takes to get there D OCT where D is distance traveled and T is time it took to get there 0 CC is the symbol for proportionality 0 When solving for the proportionality constant PC the units become clear I D S X T and to solve for the PC of S we get that DTS I The units would then be D per T your amount of distance per your rate of time ex miles per hour 0 Not all PC have units pi does not have a unit but it is a PC I Pi is a PC used to show the proportionality of the diameter of a circle to its circumference that 0 Ratio a way of expressing the quotient of two numbers usually a fraction 0 Any graph that starts at 00 and is a straight line will be a direct proportionality O The equation for a line is ymxb m is the slope which also represents the PC Chem 141 Prof Cracolice 0 Always remember to write the proportionality in the same order as specified in a problem Then from here translate it to an equation in the same order that your proportionality is written 0 Stating that two variables are directly proportional means that the graph of the variables will create a straight line through the origin 0 When adding the constant to a direct proportionality not just simply that it creates a line I Inverse Proportionalities O Inversely proportional Two quantities that are related in such a way that when one is increased by a certain number the other decreases by the reciprocal of that value I EX One variable is doubled the other is halved I One is multiplied by 3 the other is cut into thirds O Inverse proportions are very similar to direct proportions 0 Just like direct proportionalities you can add a proportionality constant PC to make it an equality I I tK X Up or T Kp It is a curved line that approaches but never reaches both the y and the X axis 0 You can change an inverse proportionality to resemble a direct proportionality creating a straight line by graphing the yaXis variable verses the reciprocal of the XaXis variable lX 0 In an indirect proportionality where you are trying to find the PC k be sure to multiply your two variable values together and find the units of k as well I P 0c lh so Pkh I To find the constant divide both sides of your equality by h I Phk so 12X448 and People X hours people hours I The second unit is always plural while the first remains singular I Be sure that the constant is indeed constant by testing all of the data points given using this method 0 Multiple Proportionalities 0 Multiple Proportionality When one quantity is proportional to each of two of those variables or more variables then it is proportional to the I CochandCocPthusCochXP Chem 141 Prof Cracolice I Equality C k X P X h 0 The units would be found the same way as in a direct proportionality I CkXPXhfindk I CP X h k so in this example the units would be k cupcakespeople hours 12 How is Algebra Used to Calculate in the sciences I a way to use conversion factors to fine the final answer 0 Key point quantity is the product of a numerical value and a unit 0 OR Always start by figuring out what the problem gives you this is called the given quantity 0 This can always be counted or measured 0 Next figure out what the problem is asking you to find or the wanted quantity 0 This will usually contain both a numerical number as well as the accompanying units 0 The problem will usually give you the units for the answer 0 Definitions are useful for most problems 12 inches 1 foot 0 Some will only be useful for the specific condition of the problem 0 Conversion factor using a direct proportionality in quantity algebra in a problem solving procedure and is eXpressed in a fraction form 0 Most conversion factors are equal no matter how your write it 1 foot 12inches 12 inches or 1 foot 1 Identify the numerical and units of the give and the units of wanted 2 Then using the correct conversion factors set up an equation that will cancel out all of the unnecessary units and leave you with only the unit for the wanted answer 3 Then plug it all into a calculator and you have your answer 0 If you are having trouble figuring out what units are left or that you still have cross out the units you know cancel 0 I how many pieces of chocolate are in a box if one bar has 8 pieces of chocolate and 12 bars fit in a box I Given 8 pieces of chocolate in a bar 12 bars in a box I Wanted the number of pieces of chocolate in one box 1 Z O 8 pieces of chocolateE a z 12 bars 1 box I Equation X6 Chem 141 Prof Cracolice I We can determine that the answer is 96 pieces of chocolate in a box because we can cancel out the units to get pieces per box Be sure when you are writing any type of quantity algebra problem you always include the units on everything Also most of your answers are going to round up because you rarely can have 232 of a variable Lesson 2 How do Scientists Express Ratios and Measure Quantities Book notes 9215 2 How do Scientists Reason and Calculate When Using Ratios Ratio the value of the partial quantity divide by the value of the whole quantity Ratios are expressed as the number of parts of a collection with characteristics divided among the whole Relation of two values Can be expressed as a decimal number dividing top by the bottom Percentage not associated with a specific number Percent references a specific number Ratio can be expressed as a percentage Can convert from a fraction ratio to percentage without going through the decimal form If percentage is given process can be reversed so you get a fraction directly from the percentage form 0 multiplying by 100 to get percent changes to dividing by 100 to get decimal 35 35 35 o gt400 35 the reverse 100 Z 100 65 1 0 100 65 00 65 When applying percentages to chem problems make sure to include all units because they are a part of the quantity too not just the numbers 170 g sugar 0 100 g solution 0 Numerator part quantity 0 Denominator number of total parts in the collection Always specify given and wanted in all problems Set up quantity algebra problem starting with your total grams of solution Each quantity should be treated as a product of a value and unit though the process of cancelation you end up with the correct units Chem 141 Prof Cracolice When working with very small numbers millionths or billionths the numbers break down to ppm or ppb 45 10645 0 I 1000000 ppm 0 In this example we multiply by 106 because it that shows one onemillionth so it cancels out the denominator to get ppm 0 45ppm is equivalent to 450 ppb Ppm is some number multiplied by 109 Ppm or ppb is used based on the nature of the mixture Only use the abbreviations if it makes sense to They are very small and not always necessary to be used Be sure to include the conversion factors especially those said in the problem Always specify given and wanted before beginning quantity algebra 22 What System of Measurements is Used by Scientists Standard units of measurements for scientists comes from the metric system Measurements of length width and powers of 10 are used to modify units Powers of 10 are all in prefixes see book for complete table Most important Notation Prefix Number Weight measure of the attractive force it experiences in a gravitation field Mass measure of resistance to change in a state of motion Both dependent on amount of matter Weight and mass can be interchangeable in the eld of chemistry Kilogram standard unit of mass in metric system Kilogram is almost equal to the weight of a one liter soda bottle Gram the base unit of a kilogram g Kilogram kg Unit of measure is a meter which is longer than a yard Meter distance that light travels in a vacuum When solving a problem state the given and wanted as abbreviations The abbreviations allow for use of scientific notation o I 2 6gtIlt103 Chem 141 Prof Cracolice Measuring volume determining the height width and length and then using the correct formula to find the space that an object takes up liter L ldm3 cubic decimeter lmLlcm3 Lesson 3 What is Science Book Notes 9415 3 Why do Substances Burn Always start anything to do with science with observations Terra pinguis combustible earth that was found in all ammable substances this is the first thought as to why substances burned This was a hypothesis Hypothesis proposed explanation for a pattern found in nature Terra pinguis was changed to be phlogiston Parts of the scientific method 0 l as a question about the natural world 0 2 take measurements qualitative testing or quantitative measurements 0 3 Look for a pattern in your data that expresses some sort of relationship 0 4 Propose a hypothesis based on an unobservable causal entity Unobservable refers to invisibility of an entity something that is not physical or too small to observe Casual entity is the underlying cause of something or some pattern in nature Entity something known or known or inferred to exist Hypothesis could be based on proposing the extreme of an unobservable causal entity Hypothesis should also be tested with further experimentation O I phlogiston hypothesis changed because the candle experiment showed that a candle would burn out in a closed container before the wax would be gone Chem 141 Prof Cracolice 0 Phlogiston was thought to be released through the burning and the air could only hold so much of it before it stopped the candle from burning More tests discovered that some metals could burn O I magnesium the ash remained the same weight as the original piece of magnesium Because of the burning of magnesium the phlogiston hypothesis changed yet again 0 I suggested that the phlogiston had a negative weight causing overall net gain within substances burned Heating magnesium oxide until it was red hot caused bright sparks to be produced when hat charcoal dust passed through it He discovered that with this gas objects burned better mice lived longer and he felt light headed when he breathed a lot of it in It was produced by heating calcinated mercury Called it a dephlogisticated air Preformed an experiment where he discovered that calcinated mercury could go from a liquid stage to a solid stage and back again when heated He thought that the phlogiston hypothesis was the best explication but he decided that it had to be a substance with a positive weight that caused substances to burn Substances burn because they react with oxygen This whole experiment is an example of what science is Every time a hypothesis is formed it must be tested and then slightly changed to fit the new result Experiment purposeful manipulation of the natural world that wants to test a specific hypothesis 32 What is the Relationship Between the Volume and Pressure of a Gas Pressure comes from strength and area over which its spread which is Force Pressure depends on force Pressure depends on area as Well Because of the relationships between pressure force and area we can write a multiple proportionality o For Fand Poc 1Athen Volume of air is proportional to the inverse of pressure This is known as Boyle s Law Chem 141 Prof Cracolice 0 V or JP This is only true if the temperature remains constant 0 VkP I PV k this shows that the product of pressure and volume will always be a constant so we could compare a before and after pressures and volumes because they will have to equal the same constant Law Statement that summarized a pattern found in nature If one factor either pressure or volume increases by a factor then the other factor must decrease by lthat same factor If pressure or volume changes then the product will change as well but because they will equal the same constant no matter what you can use the equation P1 and V1 being the initial measurement of pressure and volume P2 and V2 are the measurement after the change Mercury Barometer measure the atmospheric pressure 0 Newton s Second Law Force is equal to mass times its acceleration O FMA 0 Mass measured in Kg and acceleration measure in ms2 meters per second per second then force is in Kgms2 0 Area is expressed in m2 then we have a Pascal Pa 33 What Hypothesis Explains Boyles Law 0 Bernoulli s hypothesis only slightly explains Boyles law 0 He thought that a gas might be made of millions of tiny particles that are undetectable by the human eye These undetectable particles were later called molecules Molecules are always moving Kinetic molecular hypothesis matter is composed of miniscule particles that are in constant motion Bernoulli said that heat was the e ect of the kinetic energy of the molecules The faster they move the more heat would be let off 0 When volume is decreased there is less surface area but the number of particles and the average speed remain the same the same force is exerted over a smaller area which increases the pressure 34 What is the Relationship between Volume and Temperature of Gas 0 Temperature is the measure of the hotness of an object or a substance 0 The faster the particles move around the hotter the substance is Chem 141 Prof Cracolice Extrapolate to extend beyond the range of the data Because of Bernoulli s model and experiment we know that absolute zero the temperature where there is no volume to a substance is 273 15 0C because that is where his data would have cross the x axis indicating there was no volume William Thomson suggested an absolute value scale Kelvin K Charles law show the relationship between volume and temperature Volume and temperature are directly proportional Charles law is explained by the Kinetic Molecular Hypothesis Theory a hypothesis that is found to explain broad group of related events Kinetic molecular theory is the same thing as the Kinetic molecular hypothesis V1 V2 TTTZ 35 How can Boyles Law and Charles Law be Combined into a Single Law If V oc 1P and V oc T then V oc TIP 0 V kTP o kPVT The Ratio of pressure and volume to temperature is a constant amount If ever changed then they can be set equal to each other because both the before and after sets of data will equal the same constant this is the combine gas law With the combined gas make sure to convert the temperature to Kelvin

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