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Significant Figures. Agenda Review elements Notes on Significant Figures Practice. Alkali metals. Alkaline Earth Metals. Boron Family. Carbon Family. Nitrogen Family. Oxygen Family. Halogens. Quiz. Flip PT. New Elements. Accuracy? Precision?. Formula for % composition?. ?. ?.
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Significant Figures Agenda Review elements Notes on Significant Figures Practice
Quiz Flip PT
Accuracy? • Precision?
Significant Figures Date:
Types of Numbers • Counting • Numbers without units (whole numbers) • Ex: there are 6 chairs in the front row • Measured • Numbers WITH units (actually measured) • Ex: 58.35 g • Defined • Fractions or conversion factors • Ex: 12 inches = 1 foot, 2.54 cm = 1 inch
12 people 5.34 g 16 Tbsp in a cup 6 cans 16 oz in a pound 2.54 cm in an inch 40.75 in 2.25 cm Determine the type of #Discuss with table partner
SF in numbers • Counting – infinite, ∞ • Defined – infinite, ∞ • Measured – where the fun begins! • Digits 1 – 9 ALWAYS count
12 people 5.34 g 16 Tbsp in a cup 6 cans 16 oz in a pound 2.54 cm in an inch 40.75 in 2.25 cm Determine the # of SFDiscuss with table partner
SF for measured # • Zeros SOMETIMES count • LEADING zeros NEVER COUNT • 0234 • 0.034 • MIDDLE zeros ALWAYS COUNT • 101 • 5.001 3 SF 2 SF 3 SF 4 SF
SF for measured # CONT • TRAILING zeros count if a decimal is present • 100.0 • 0.900 • 100 4 SF 3 SF 1 SF
0.031 or 3.1*10-2cm 6.00 cm 107.05 cm 2.35*10-3g 12.05 mL 0.14 cm 3.01 cm 5.790 g Determine type of ZERO, then # SFDiscuss with table partner
12.0 cm +2.45 cm 14.45 cm Round to tenth 14.5 cm 5.79 g -3.2 g 2.59 g Round to tenth 2.6 g SF in Calculations • Addition and subtraction • -Round to least number of decimal places
SF in Calculations CONT • Multiplication and division • Round to least number of SF 6 cm *6 cm 36 cm2 Round to 1 SF 40 cm2 122.5 g/mL 2.0 mL = 61.25 g Round to 2 SF 61 g
Homework • Complete SF worksheet • Work on elements • Quiz next Friday before Test • Lab Report • Rough Draft due Monday • Final Draft due Wednesday • Test next Friday