Significant Figures

Significant FiguresAgenda

•Review elements

•Notes on Significant Figures

•Practice

The Periodic Table of the Elements

IA IIA IIIB IVB VB VIB VIIB VIIIB IB IIB IIIA IVA VA VIA VIIA VIIIA

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

Significant Figures

December 17, 2007

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

Determine the type of #Discuss with table partner

• 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

SF in numbers

• Counting – infinite, ∞

• Defined – infinite, ∞

• Measured – where the fun begins!

– Digits 1 – 9 ALWAYS count

Determine the # of SFDiscuss with table partner

• 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

SF for measured #

• Zeros SOMETIMES count– LEADING zeros NEVER COUNT

• 0234• 0.034

– MIDDLE zeros ALWAYS COUNT• 101• 5.001

2 SF

3 SF

3 SF

4 SF

SF for measured # CONT

– TRAILING zeros count if a decimal is present• 100.0• 0.900• 100

4 SF3 SF

1 SF

Determine type of ZERO, then # SFDiscuss with table partner

• 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

SF in Calculations

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

•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

Significant Figures

Documents

Transcript of Significant Figures