Chapter 1 7 1 14 9 3 13 Chemistry is quantitative Physical quantities both a number and a unit of defined size is required to describe physical quantity Scientific notation convenient way to write a small large number Almost all units will be metric Length meter Volume L Mass g Time seconds Temperature celcius kelvin Some could be SI M cubic meter kh second kelvin Volume is space occupied by a substance L 1 06 q Cubic meter is the Si system cubic centimeter Mass quantity of material in sample Grams all the way to kilograms Measurement is as important as instrument measuring it Last digit is obtained by estimating First estimated is also significant Significant figures Known estimated Depends on instrument Zeros Sandwiched zeros between two non zeros always significant o 2001 Two zeros sig Trailing zeros without decimal are NON SIG o 25000 has TWO sig figures unless explicitly stated Leading zeros precede non zero digits in decimal number are NOT SIG o 0 000262 has THREE sig figures Sig figures in Scientific Notation All digits including zeros in coefficient are significant Prefixes A prefix in front of a unit increases or decreases the size of that unit making units larger or smaller than the initial unit by one or more factors of ten o 1 Kilo meter 10 3 meters Memorize o K Deci centi milli micro and nano K 10 3 0 035 Deci 1 10 1 Centi 01 10 2 Milli 001 10 3 Micro 000001 10 6 Nano 000000001 10 9 2 75 350g Equalities Use two different units to describe the same measured amount Equalities can be written for relationships between units of the metric system between U S units or between metric and US Units o 1m 1000 mm o o 1lb 16 oz 2 20 lb 1kg Converting a quantity from one unit to another starting quantity X conversion factor Equal quantity A conversion factor 1 in 2 54 cm 1in 2 54 cm Know 2 5 hours Need to know minutes 1hr 60 min 60 1 2 5h X 60 min 1hr 150 minutes Most will use two or more factors Unit 1 Unit 2 Unit 3 Unit 1 X Unit 2 Unit 1 X Unit 3 Unit 2 Unit 3 Canceling units helps with checking 55mi 1 hr 1 min 5280ft 1 hr 60 min 60 sec 1 mile 81ft per second