Warm –up #2 What is chemistry? Write what you recall about the definition and name 2 areas of study of chemistry.

Significant figures

Significant figures What about when you receive data from another scientist? “The carbon nanotube was 27 cm long” “The carbon nanotube was 27.3 cm long” “The carbon nanotube was 27.31 cm long” “The carbon nanotube was 27.312 cm long”

Significant figures Significant Figures (Sig Figs): include all the numbers that are known precisely plus one last digit that is estimated

Rules for Determining the Significant Figures .RuLE•1. All non-zero digit are significant. •Example (Ex): 3.45 has 3 sig figs

Rules continues.... 2. Zeros between non-zero digits are significant Ex: 5.091 has 4 sig figs (the zero is between non zero digits) 3. Zeros appearing in front of all non-zero digits are NOT significant Ex: 0.45 has only 2 sig figs

Rules continues ….......... 4. Zeros at the end of a number and to the right of a decimal point are significant •Example: 3.40 has 3 sig figs •*The zero after a decimal point is significant only if a non-zero digit precedes it

Rules continues..... 5. Zeros at the end of a measurement and to the left of the decimal point are not significant unless the zero was measured Example: 300 has only 1 sig fig 300.0 has 4 sig figs

Determine the number of sig fig: a. 10.5 g b. 112 mL c. 0.065 kg d. 2 527 cm e. 0.000 480 59 mg f. 12.000 m g. 1000 g

Review Determine the number of sig figs in: a. 456 b. 4.00 c. 6.090

Practice •Place the following numbers into 3 sig figs • 1) 45.2367 • 1) 45.2367 2) 1.238 3) 7454560000 4) 0.054287 5) .00003456000

Practice How many sig figs are in following: 1)0.001256 g 2)200.3 kg 3)1.520 4)100 230 082 000

Practice •Write the following into three sig figs: a)134243.05 b)1.245 x 10-3 c)9.9003 d)0.0002345

Rules for Sig Figs in Calculations •An answer cannot be more precise than the least precise measurement from which it was calculated •Basically, if you have to do a calculation with sig figs, your answer cannot be more precise than your least precise measurement

Multiplication and Division Multiplication and Division: The number of significant figures in the answer (result) is the same as the number of significant figures in your least precise measurement

Example Problem Report 6.3 * 6.45 * 8.589 with the correct amount of sig figs

Solution

Additional Practice a. 2.7 / 5.27 b. 4.5 * 9.56 c. 2 * 5.6 d. 2.33 x 6.085 x 2.10 e. [(9.714 x 105) (2.1482 x 10-9 )] [(4.1212) (3.7792 x 10-5)]

Rules for Addition and Subtraction Addition and Subtraction: The answer (result) has the same number of decimal places as the least precise measurement

Example Problem •12.11 + 118.0 + 1.013 •1. Determine which measurement is least precise •2. Calculate •3. Place in correct number of sig figs

Practice Report the following answers with the correct amount of sig figs: 1. 45.69 - 23.156 2. 12.35 + 47.360 + 12 3. 105.36 - 65.890 4. 3.461728 + 14.91+ 0.980001+ 5.2631 5. 23.1 + 4.77+ 125.39 + 3.581 6. 22.101 – 0.9307

Practice Place the following equations in proper significant figures 1)13.004 + 3.09 + 112.947 2) 1.23 m * 0.89 m = 3) 7.987 m – 0.54 m 4) (2.95 x 107) / ( 6.28 x 1015)

Practice Place in the proper sig figs 1)23.27 -12.058 2)3.15 x 2.5 x 4.00 3)36 / 0.62 4)13.25 + 10.00 + 9.6 5)25.37 + 6.850 + 15.07 + 8.056