Week 2 Book Notes
Week 2 Book Notes Chem 141
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This 5 page Class Notes was uploaded by Cassidy Zirko on Saturday September 12, 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 40 views. For similar materials see College Chemistry 1 in Chemistry at University of Montana.
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Date Created: 09/12/15
Chem 141 Week 2 Prof Cracolice Chapter 4 How do Scientists Make Report and Work with Quantitative Measurements 9915 Vocab words Things to keep in mind 41 How is Uncertainty in Measured Expressed Experiments are run many times in order to minimize the errors that could be introduced Most scientists repeat measurements three to five times Precision reproducibility of the results Perfectly precise measurements Will have all the same values Accuracy a measured closeness to the correct value All measurements Will vary near the actual value at the quantity being measured if in a series Just because data is precise it doesn t mean that its accurate No absolutely guaranteed method Will get both precise and accurate results in a chemistry experiment There is always some degree of judgement in interoperating the data What is the Convention for Expressing Uncertainty in Measurement Significant gure Convention universally agreed upon custom about expressing the accuracy of measured quantities Uncertain number last digit in a number Measure is to the recorded With all digits known and one uncertain digit 0 I 124 cm 3 sig figs 2 known 12 one uncertain 4 0 00000543 I still 3 sig figs zeros are place holders Zeros between the decimal point and first non zero are place holders not significant Can use scientific notation to eliminate the extra zeros f o I 425000000 425 x 108 You never know what the uncertain digits could be so writing it in sig fig and scientific notation reduced the option of being wrong Exponential notation must be used to express a measured quantity that ends in ain a zero before the decimal Chem 141 Week 2 Prof Cracolice A number is also ambiguous if it has many zeros because you don t know if the uncertain number is in the millions place or the ones place Calculated result cannot be more precise than the measurements that it s based on Rounded off a ways to correctly represent the uncertainty of the measurements that they are based on 0 If the first digit is below 4 then the number remains unchanged 0 If the first digit is a 5 or more then round the number up one 0 Round off a sum or difference to the highest valued column that has the uncertain digit OR 0 Round to the least amount of decimal places in adding and subtracting 0 In multiplication or division round to the total smallest amount of sig figs in any number including those after the decimal O I 2433l 75 two sig figs because the lowest number of sig figs in the equation is 2 0 When addingsubtracting and multiplyingdividing then apply each rule separately depending on what operation you are doing in the problem 42 How is the Relative Heaviness of a Substance Expressed 0 Absolute terms the amount one thing weights is exactly the same as the same amount of another thing 0 I 1 lbs rocks 1 lbs feathers 0 Volume differs even if mass is the same 0 Relative heaviness of a substances Density 43 What is the Relationship between the Metric System and the US system of Measurement 0 The US uses the United States Customary system USCS USCS is defined in terms of metric 0 Conversions between the two systems occur through quantity algebra MGtTiC39 USCS COHVGY 51011 Table USCS USCS Conversion Factors Length Mass Volume Length 1 mCh 23954 cm 1ft212in 1 lb 1602 1 qt 2 pt Mass 1 1b 45359237 g 1 yd 3 ft 1 qt 32 fl oz 1 ml 5280 ft 1 gal 4 qrt Volume 1 gal 3785411784 L only measured quantities establish number of sig figs needed in answer Chem 141 Week 2 Prof Cracolice Use at least one digit ore than the measure quantity in the conversion 0 convert 32 lbs to grams use at least 4530 if not more digits in your conversion Pressure is either in atm or mmHg 0 146959488 psi USCU 1 atm metric 44 What Quantitative Problem Solving Strategies are used by Scientists Key in chem is to be a good problem solver Try and look at problems you are stuck on in different ways Quantitative problems those problems involving quantities calculators are usually used when solving these types of problems Always include units and cancel units in setups Algorithm step by step procedure to solve a problem Being able to recognize the necessary steps but having to use calculations to solve the problem Not all problems can be solved by algorithms True problem no algorithm can be applied Cant quickly recognize how the problems needs to be done Harder and more challenging All about learning how to solve not just getting the right answer Chapter 5 How do Scientists Classify Matter 91115 Water always affects you no matter what Life depends on water Plastics are made from petroleum 51 How do Scientists Classify Matter Petrochemical substance that is made from petroleum or other close related substances crude oil or natural gas Very many things are made from petrochemicals Petroleum one source which forms petrochemicals O 3 major natural substances extracted from the earth Matter describes physical materials in general Matter can be classified according to a scale Liquid form takes shape to the container fairly constant volume over temperature ranges Indefinite shape definite volume Properties something matter has which helps categorize it Petroleum is in liquid state Chem 141 Week 2 Prof Cracolice Solid water is ice and snow Solid definite shape and volume and doesn t not change state with temperature Gasvapor variable shape and volume molecules have more space to move around because the speed at which they are moving overcomes their desire to be together Condensation of water happens when the water vapor is cooled by the water in the glass Could be called humidity quantity of gas molecules of water in the air Solid phase water molecules are stuck together to so you get a solid shape 0 I ice cube Liquid phase molecules would be able to move around but would still be stuck together 0 I liquid water Gas phase water molecules would be free to move around themselves independent of one another Pure substance a substances with no dissolved substances a kind of matter 0 All pure substances have distinct composition Pure water I leads to production of hydrogen and oxygen molecules 0 Compound a substance that can be decomposed into simpler substances 0 Element pure substances that cant be decomposed into another pure substances by ordinary chemical means Crude oil petroleum right after it is pumped out of the ground complex mixture of many substances Mixture combo of two or more substances that doesn t have a fixed composition 0 I chocolate chip cookie dough Solution homogenous mixture or heterogeneous mixtures O I ice in a glass of water 0 Oil and water 0 Distillation process of separating the components of a mixture based on boiling points and collecting the gas components that end up separated 0 Cracking fraction of a substance is transformed or cracked into another 0 Ex lubricating oil I gasoline Chem 141 Week 2 Prof Cracolice 0 We depend on chemical changes for almost all energy
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