1 / 12

Why are sig figs important?

Why are sig figs important?. They communicate the precision of the measuring tools used by the chemist. They determine how precise the answers to calculations (using the measurements) can be. Significant Figure Rule 1. All non zero numbers are always significant. 1 2 3 4 5 6 7 8 9.

cwhitlock
Download Presentation

Why are sig figs important?

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Why are sig figs important? • They communicate the precision of the measuring tools used by the chemist. • They determine how precise the answers to calculations (using the measurements) can be.

  2. Significant Figure Rule 1 All non zero numbers are always significant. 1 2 3 4 5 6 7 8 9

  3. Significant Figure Rule 2 Zeros between non-zero numbers are always significant. (Sandwich zeros) 101

  4. Significant Figure Rule 3 Leading zeros are never significant. 0.000000000009 08 0.1

  5. Significant Figure Rule 4 Trailing zeros are sometimes significant. 900 900. 9.00 If you put a decimal at the end the zero ARE significant. You are saying I know it is exactly 900. Zeros at the end of a decimal number are significant. DON’T WRITE THEM IF YOU DON’T KNOW THEM!!!!! Zeros at the end of a whole number are NOT

  6. Circle the numbers that contain 3 sig figs: 900 807 234 67.1 0.87 28 1020 84 0000000765 0.0000341 900030 78 721 09

  7. Practice! • Determine how many significant figures each has • 25.2 cm = • 35.0 s = • 0.0044 kg = • 30200 m = • 2.5 x 1012 mL =

  8. Sig. Figs in Calculations Multiplying or dividing – the number of significant figures in the answer must be the same as the smallest number of significant figures for any one of the numbers in the calculation. Ex: What is the density of an object with a mass of 10.00 g and a volume of 3.3 ml? 3.0 g/mL

  9. Calculations • (400)(206)= • (4.236)/(2.10)= 80,000 2.02

  10. What about (+) and (-)? Adding or subtracting – the number of decimal places(precision) in the answer must be the same as the smallest number of decimal places (least precise) measurements used to make the calculation. Ex: 1.013 mm + 12.14 mm + 8.0 mm = 21.2 mm

  11. Whole Numbers Ending in 0?Best to use Scientific Not. A whole number ending in zeros (like 2000) only has one sig. fig. But often people mean for it to have more. To avoid confusion scientific notation should be used. 2.0 x 103 two sig. fig 2.00 x 103 three sig. fig 2.000 x 103 four sig. fig

  12. Calculations • (4x102)(2x103)= • (4.2x102)/(2.10x10-4)= 8 x 105 2.0 x 106

More Related