Significant Figures Part 1: Counting Sig figs

Decimal--Left 0.004703 has 4 significant digits.  If a number has a decimal, count all digits starting with the first non-zero digit on the left. Examples: 0.004703 has 4 significant digits. 18.00 also has 4 significant digits.

No decimal--right If there is no decimal , count all digits starting with the first non-zero digit on the right. Examples: 140,000 has 2 significant digits. 20060 has 4 significant digits.

In both cases, start counting with the first non-zero digit. 00.015 15000

Another way of thinking… These number are always significant: All NON-ZERO numbers (1-9) Trapped zeros (6007) Trailing zeros when there is a decimal (26.00)

Complete Sig Fig Self Test Now Try it on your paper a) 3.57 m _________ b) 20.040 g _________ c) 0.004 m3 _________ d) 730 000 kg _________ e) 12 700. mL _________ f) 30 atoms _________ g) 0.6034 g/mL _________ h) 19.0 s _________ i) 810 oC _________ j) 0.0100 mol _________ k) 0.0040 km _________ l) 8100.0 cm3 _________ Complete Sig Fig Self Test

Significant Figures Part 2: math with Sig figs

This leads to 2 rules: add/subtract & multiply/divide Math with sig figs Calculations shouldn't have more precision than the least precise measurement. This leads to 2 rules: add/subtract & multiply/divide

Addition and Subtraction The answer should not have more decimal places than the number with the least decimal places. Example: 1.2 + 12.348 = 4.2 + 8.579 =

Addition Practice A) 345.6 + 456.78 = B) 4.42 + 8.576 = C) 23.456 + 0.04 = D) 78.2 - 40 = E) 87.9 – 20 = F) 478.84 – 119 =

Top half of practice sheet (Addition and Subtraction sets only) Assignment Top half of practice sheet (Addition and Subtraction sets only)

2. For Multiplication and Division The answer should not have more significant figures than the number with the least amount of significant figures. Example: 502 x 3.6 = 1807.2 1800

Multiplication Practice A) 238.1 x 402 = B) 500.1 x 75.2 = C) 23.02 / 45 = D) 5300 / 456 = E) 4590 / 1234 = F) 141 x 920.0 =