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Significant Figures General or Intro to Chemistry I Rules for One Value • 1) numbers 1-9 are significant • Zeros: – Before – not significant – Between – Significant – End – when there is a decimal any where – significant – When there is no Decimal anywhere they are not significant Can you Follow? • Determine the number of significant figures: – A) 0.003204500 Rule 1) 0.003204500 four sig figs Zeros: Beginning 0.003204500 3 but not sig figs Between 0.003204500 one sig figs end 0.003204500 two sig figs because of decimal 0.003204500 has seven significant numbers Lets Practice! • Determine the number of significant figures in each of the following measurements. a) 48077 mi 5sig. figs. b) 56 ml 2sig. figs. How did you do? Are you c) 0.0000030g 2 sig. figs. ready to move on? If not please go over the rules and d) 29000. ton 5 sig. figs. practice till you drop. e) 15000g/cm3 2 sig. figs. f) 4.0100x10-4 5sig. figs. Rules for More than One Value • When adding or subtracting the answer reflects the value with the least number after the decimal. • When Multiplying of dividing the answer reflects the value with the least significant number. • When there is a combination always follow the order PEMDAS (Parenthesis, Exponents, Multiplication or Division, Addition or Subtraction). Can You Follow? • Addition/Subtraction Multiplication/Division 89.332 2.8 X 4.5039= + 20.0## 12.61092 109.332 Answer: 13. answer: 109.3 Please be aware that both answers always consider the least number of value but only Multiplication/Division followed significant figures. Did you also notice that addition /subtraction reported more values that the numbers given? Lets Practice! Carry out the following mathematical Operations and express answers in correct significant figures. a) (4.20x10−4) + -4 (3.564x10−11) =4.20000x10 = 4.20x10-4 b) (0.00950) x (8.501x107) ÷ 3.1425x10−11 = 2.56991x1016 c) (2.420𝑔 + 15.6𝑔) ÷ 4.8𝑔 = 3.7541667 = 3.8 Warning: When rounding some professors follow the following rule It the digit remove is 5, the preceding number is increased by 1 if is add and unchanged if it is even = 2.57x1016 Hope that Help! • Practice the rules when ever you have a chance and you will do great! Practicing over and over and over…. is the way to remember! If you still have questions please stop by the Science Tutoring Lab. LOH 230