CHM 1020 Chp 2 and Week 2 Notes
CHM 1020 Chp 2 and Week 2 Notes CHM 1020
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This 3 page Class Notes was uploaded by Rachel Belson on Thursday January 21, 2016. The Class Notes belongs to CHM 1020 at Wayne State University taught by Maryfrances Barber in Fall 2015. Since its upload, it has received 15 views. For similar materials see Survey of General Chemistry in Chemistry at Wayne State University.
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Date Created: 01/21/16
Chapter 2 Tuesday, January 19, 2016 5:05 PM Notes from Chapter 2, as well as points from lecture. 2.1 Measurement systems A. Measurement: determination of the dimensions, capacity, quantity, or extent of something. B. English System (commerce): a. Inch, foot, pound, quart, and gallon C. Metric System a. Grams, meter, liters 2.2 Metric System Units A. Base units i. Meter, gram, liter ii. Multiples of the unit are made up by adding prefixes Multiples/powers of 10 giga G 10 9 mega M 10 6 kilo k 10 3 deci d 10 -1 -2 centi c 10 -3 milli m 10 micro µ 10 -6 nano n 10 -9 pico p 10 -12 Reminder: Mass: Measure of total quantity of matter in an object Weight: measure of the force exerted on an object by gravitational force 1 microgram= 10^(-6) gram 1 kilometer= 10^(3) meters 1 Gs= 10^(9) seconds 1 pm= 10^(-12) meters 1 cm= 10^(-2) meters From Lecture: EQUIVALENCE STATEMENTS Conversion factor=unity rates=1 A. Come from equivalence statements B. 1 kilometer=10^(3) C. Decide so the units cancel out Exam 1 Page 1 2.3 Exact and Inexact Numbers Exact numbers- A number that has no uncertainty Inexact/measured numbers- A part that is exact and a part is estimated. The number has a degree of uncertainty 2.4 Uncertainty in Measurement and Significant Figures It is important to remember when taking measurements that only one estimated digit is ever to be recorded. The level of uncertainty in a measurementis indicated by the number of significant figures recorded. Significant figures: Digits in a measurement that are known with certainty, plus one estimated digit. Number of Sig Figs= all certain digits + one estimated digit Rules of Sig Figs A. In any measurement all nonzero digits are significant. B. Zeros a. Leading Zeros, those at the beginning of the measurement, are NEVER significant i. 0.0141 ii. 0.0000000065 b. Confined zeros, those between two nonzeroes, are ALWAYS significant i. 3.076 ii. 0.001003 c. Trailing Zeros, those at the end of the number, are significant if there is a decimal point, and are not significant if the measurementlacks an explicit decimal i. 56.00 ii. 0.05050 iii. 59,000,000 iv. 6010 2.5 Significant Figures and Mathematical Operations Rounding off is the process of deleting unwanted (insignificant) digits from calculated numbers. 4 or less, drop the digit and those below it. 5 or more, that digit and all that follows are dropped, and the last sig fig is increased by one. Rounding to two sigfigs: a. 25.7 becomes 26 b. .4327 becomes .43 c. 432,117becomes 4.3 x 10 or 430,000 d. 13,500 becomes 14,000 Operational Rules Exam 1 Page 2 Operational Rules 1. Multiplicationand Division a. The number of sig figs in the answer is the same as the number of sig figs in the measurement that contains the FEWEST sig figs b. 6.038 x 2.57 = 15.5177=15.5 2. Addition and Subtraction a. The answer has no more digits to the right of the decimal point than are found in the measurement with the fewest digits to the right of the decimal point. 9.33 + 1.4 = 10.733 10.7 2.6 Scientific Notation Scientific Notation: a numerical system in which numbers are expressed in the form A x 10 , where A is a number with a single nonzero digit to the left of the decimal place, and n is a whole number. A is the coefficient, and n is the exponential term. Scientific Notation and Sig Figs:Only significant figures are in the coefficient To multiply exponential terms, add the exponents. To divide exponential terms, subtract the exponents. (2.33 x 10 ) x (1.55 x 10 ) First multiply the coefficients, and get 3.6115, becoming 3.61. 7 Add the exponential terms and get 3.61 x 10 2.7 Conversion Factors Conversion Factor: a ratio that specifies how one unite is related to another, for example 1 min = 60 sec. 2.8 Dimensional Analysis Dimensional Analysis:a general problem solving method in which the units associated with numbers are used as a guide in setting up calculations. SEE HANDWRITTEN CONVERSIONS ABOVE FROM LECTURE 2.9 Density Density: the ratio of the mass of an object to the volume occupied by the object. D= M/V 2.10 Temperature Temperature: the indicator of the tendency of heat energy to be transferred from one object to another Celsius Scale- most commonly used. Boiling water=100, Freezing water=0 Kelvin Scale- units of kelvins instead of degrees. Boiling water=373 K, Freezing water=273 K Fahrenheit scale- smaller degree size than other two. Boiling water= 212, Freezing water= 32 Conversions: a. K = C + 273 b. C = K -273 c. F = (9/5)( C ) + 32 d. C = (5/9) ( F - 32) Exam 1 Page 3
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