MEASUREMENT

1. MEASUREMENT Units of Measurement

2. Types of Data Data refers to information Qualitative Data Describes something Texture, Color, etc Quantitative Data Measures Something Length, Mass, Time, etc

3. Determine if each of the following is a qualitative or quantitative measurement. • The sandwich has ham in it. • There are four eggs in the carton. • I used 230 grams of NaOH. • I added water to the solution.

4. Measurement A quantity with both a NUMBER and a UNIT Provides a reference point NO NAKED NUMBERS!

5. Number vs. Quantity • Quantity = number + unit

6. Measurements Accuracy How close a measurement comes to the accepted answer Precision How close a series of measurements are to each other. How specific an measurement is 10 vs. 10.01 vs. 10.007

7. Let’s use a golf analogy

8. Accurate? No Precise? Yes

9. Accurate? Yes Precise? Yes

10. Precise? No Accurate? No

11. Accurate? Yes Precise? We can’t say!

12. Accurate? Precise?

13. Accurate? Precise?

14. Accurate? Precise?

15. Error • Accepted value – The right answer • Based on reliable references • Also called Theoretical Yield • Experimental Value- what you get in lab • Also called Actual Yield

16. Measurements Determining Error How far your measurement is from the accepted value.

17. Percent Error

18. International System of Measurements

19. Prefix Symbol Factor kilo- mega- k M 103 106 BASE UNIT deci- d --- 100 10-1 centi- c 10-2 milli- m 10-3 micro-  10-6 nano- n 10-9 pico- p 10-12

23. Significant Figures or Digits • Significant Figures (sig figs) are all digits which show where an actual measurement is made; the more sig figs, the better the measurement: • 0.5 m (1 sig fig) • 0.50 m (2 sig figs) • 0.500 m (3 sig figs) • 0.500 m was measured with a more accurate ruler

24. Counting Sig Figs • Which digits are significant? • All non-zeroes are significant • A final zero after a decimal point is significant • All zeroes between sig figs are significant • Zeroes that are place holders are not significant and do not go into scientific notation

25. 770 mL 0.0700 mL 7070 mL 0.007 mL 7.00 x 103 mL 7000 mL 70.070 mL 77.0 mL 2 3 3 1 3 1 5 3 How many sig figs in the following measurements?

26. Math with Sig Figs • Addition & Subtraction • The answer must be rounded to the same number of decimal places as the measurement with the fewest decimal places (worst measurement). • 527.38 m • + 21.2 m • 548.58 m  548.6 m

27. Math with Sig Figs • Multiplication & Division • The answer must be rounded to the same number of sig figs as the measurement with the fewest sig figs (worst measurement). • 527.38 m (5) • x 21.2 m (3) • 11180.456 m2 11200 m2 (3)

28. Scientific Rounding Rules • 1. If the digit to be rounded is followed by 0,1,2,3, or 4 – do not round the digit / leave digit alone • 2. If the digit to be rounded is followed by 6,7,8, or 9 – round up the digit • 3. If the digit to be rounded is followed by a 5 with any digits of value anywhere behind the 5 – round up the digit • 4. If the digit to be rounded is followed by only a 5 or a 5 with no numbers of value behind the 5 – odd digits round up and even digits are left alone

29. 32980 g 0.07810 m 355 mL 345 mL 798 oC 5.92 x 1024 atoms 1450.01 km 33000 g 0.078 m 360 mL 340 mL 8.0 x 102oC 5.9 x 1024 atoms 1500 km Round the following measurements to 2 sig figs: