1. Errors in Measurements Class measurements for the density of gold (in g/mL) Group 117.8Group 418.1 Group 218.0Group 517.8 Group 317.9Group 618.0

2. Errors in Measurements Precision – Measurements close to one another. Group 117.8Group 418.1 Group 218.0Group 517.8 Group 317.9Group 618.0 Class measurements are precise….

3. Errors in Measurements Accuracy – Measurements close to correct value. Group 117.8Group 418.1 Group 218.0Group 517.8 Group 317.9Group 618.0 The actual value for the density of gold is 19.3 g/mL. So the class is not accurate…

4. [http://cwx.prenhall.com/bookbind/pubbooks/hillchem3/medialib/media_portfolio/text_images/CH01/FG01_08abcd.JPG]

5. Errors in Measurements Check your accuracy by calculating your Percent Error

6. Errors in Measurements Accepted – What the “true” value is Measured – What you found in the experiment.

7. Errors in Measurements What is the percent error for the class data then? Percent Error = 7.25% Class Avg.

8. Significant Digits What is the reading for these two volumes? 33.5 mL 30 mL 30.0 mL

9. [http://wps.prenhall.com/wps/media/objects/476/488316/Instructor_Resources/Chapter_02/FG02_07-30q.JPG] Most Accurate Cylinder? 65 mL vs. 5.50 mL

10. Significant Digits Gas Station Analogy – Gas $2.50 17.585 gal = $43.96 17.59 gal = $43.98 17.6 gal = $44.00 18 gal = $45.00

11. Significant Digits Numbers that are “given” to you must be checked for their accuracy as well. 1.0400 vs. 10400 vs. 0.00104 Atlantic-Pacific Rule – Pg. 26

12. All non-zero digits are significant Zeros depend on the decimal point 1.0400 5 significant digits

13. 10400 3 significant digits

14. 0.00104 3 significant digits

15. 6.02 x 10 23 3 significant digits

16. Significant Digits Multiply / Divide Use the smaller number of significant digits for the answer. [http://wps.prenhall.com/wps/media/objects/602/616516/Media_Assets/Chapter01/Text_Images/FG01_07-05UN.JPG]

17. Significant Digits Add / Subtract Line up the decimal places then round answer. [http://wps.prenhall.com/wps/media/objects/476/488316/Instructor_Resources/Chapter_02/FG02_04-06un.JPG]