Measurements, Significant Figures, and Unit Conversion
Measurements, Significant Figures, and Unit Conversion CHEM 111 (Section 64)
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This 4 page Class Notes was uploaded by Jaymi Notetaker on Saturday August 29, 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 73 views. For similar materials see General Chemistry 1 in Chemistry at Ball State University.
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Date Created: 08/29/15
August 24 2015 Chemistry Science that deals with the structure properties and transformation of matter Matter Anything that has volume takes up space Measurements in Chemistry Precision the closeness of the results to each other Accuracy the closeness of a single measurement to the true value EXAMPLE Poor accuracy Poor accuracy Good accuracy Good precision Poor precision Good precision August 262015 Measurements in Chemistry continued Units standard of measurements Length meter m Time second s Mass gram g Amount of substance mole mol Measurement the comparison of a unit s quantity Significant Figures Significant Figures includes all certain digits plus a final digit that has some uncertainty TWO EXAMPLES ON NEXT PAGE Oin 1in 2in 3in 4in Sin 6in Yellow Circles Certain digits 4 amp 5 Red dotted line Uncertain digit approximately 48 Why Just 53943 Why Qt 54303333333 You only need 3 5424 I numbers after the 542 5 F1nd the average of the Report as decimal for this 5442 numbers 543 problem Since 0 is the last number and it s usually not significant 1 f F 1 nterpret1ngS1gn11cant 1gures 1n Spec1a Cases SO we didn ncludeit Very Small Numbers 000000 Leading zeros are placeholders for the decimal point Not significant unless it is from a measurement Very Big Numbers 00000 Trailing zeros are usually placeholders for a decimal point Can be shown to be significant if written in scientific notation which is used to clarify Significant Numbers are highlighted In multiplication and division the smaller number determines how many significant figures left In addition and subtraction line up by decimal points and then leave off depending on the number that ends first Exact errorless number a counted or defined number Example number of students in a row Common Metric Prefixes on blue handout need to know Mass an object s quantity of matter Volume space occupied by a substance Density mass per unit volume MClSS Density volume All solids liquids and gases have a density that is a constant at a given temperature August 28 2015 Temperature The hotness or coldness of a substance K Kelvin C Celsius F Fahrenheit 37315K Bo ig point ovaater 100 C 212 F 27315 K Freezing point of water 0 C 32 F Temperature in Kelvin cannot equal 0 all motion is stopped at that point Converting Temperature 9 C to F F E gtlt C 32 5 F to C C 6 x F 32 C to K K C 27315 Kto C C K 27315 Example Convert 40 C to F note 2 significant figures 9 F C 32 5 9 F E 40 32 40 F Unit Conversion amp FactorLabel Method desired unit G1ven Un1t X de51red un1t given unit Explanation given unit cancels out leaving you with the desired unit desired unit is the conversion factor within the problem given unit Making Conversion Factors 1 km 103m or Number always goes with its unit 103m 1 km 1 km 103m so FactorLabel Method 1 Make a roadmap aka figure out where you want to go 2 Set up conversion factors 3 Check units 4 Calculate Example prefix unit to a nonprefix unit Gold Au atom has a diameter of 25 X 10 10 m Convert to nm Roadmap m to nm 1 25x 10 10 25 x 1010 m x quot1 quotm 25 x 101 025 nm 1x 10 9m 1x 10 9 note m meters cancels out and you are left with nm your desired unit Example MultiStep Conversion Grams to Tr 02 to Dollars 163 g x 311 Tag x 1276f gum 66894 dollars 669 note g grams and Tr 02 are both canceled out leaving your desired unit dollars