1. BASIC LAB MEASUREMENTS AND EQUIPMENT EXPERIMENT 1

5. For Ruler I, shown below, the smallest increment is 0.1 cm and all readings should be recorded to one-tenth of 0.1 cm, which is 0.01 cm (2 decimal places). For Ruler II, however, the smallest increment is 1 cm, and all readings should be recorded to one-tenth of 1 cm, which is 0.1 cm (1 decimal place). UNCERTAINITY DETERMINATION

6. EXAMPLE 1 What is the most accurate reading of the length of the object below measured using a ruler? Correct answer – 8.14, 8.15, or 8.16 (the uncertainty is 0.01- a tenth of 0.1 the smallest unit)

7. What is the most accurate reading of the length of the object below measured using a ruler? EXAMPLE 2 Correct answer – 8.1 or 8.2 (the uncertainty is 0.1- a tenth of 1 the smallest unit) We cannot estimate further into the second decimal place. Thus, it would be incorrect to record 8.10 cm or 8.20 cm.

8. (This should not be recorded as 5 cm or 5.0 cm, but as 5.00 cm.)

9. (This should be recorded as 5.0 cm, AND NOT 5.00 cm or even 5) Uncertainity is a tenth of 1 whole unit Because we have 10 whole number units in between markings

10. Actual volume of liquid dispensed is : 19.77 – 0.30 ml = 19.47 ml USING BURETTES

11. MEASURING MASSES LAB BALANCE ANALYTICAL BALANCE

12. LABORATORY BURNERS SETTING UP A TERRILL BURNER AND A HOT WATER BATH

14. Watch the reading if your thermometer is digital. If the reading fluctuates, the uncertainty is equal to the range of the fluctuation. For example, imagine that the temperature reading on a digital thermometer wanders back and forth from 20.12 to 20.18 degrees. Your uncertainty would be 0.06 degrees. Go to the last digit of the reading if the thermometer holds steady and constant. In this kind of situation, the last digit will be considered uncertain. If your thermometer reads 36.12 degrees, for example, the uncertainty would be 0.01 degrees, because the last digit (the 2 in 36.12) sets the limit of your precision. Watch the mercury or alcohol in the column if you are using a traditional thermometer. Read the temperature to the nearest 0.1 degree if possible MEASURING TEMPERATURE Digital thermometers Mercury thermometers

15. Counting significant figures in a correctly reported measurement 1.All nonzero digits are significant. e.g. 1,2,3 2.Interior zeros (zeros between two numbers) are significant. e.g 4.0304 3.Trailing zeros (zeros to the right of a nonzero number) that fall after a decimal point are significant. e.g. 6.50, 4.00 4. Trailing zeros that fall before a decimal point are significant. e.g. 70.00, 1000.34 5.Leading zeros (zeros to the left of the first nonzero number) are NOT significant. They only serve to locate the decimal point. e.g. 0.00007 (one significant digit only!!) 6.Trailing zeros at the end of a number, but before an implied decimal point, are ambiguous and should be avoided. e.g. 350 should be written as 3.5 x 10 2 (indicates two significant figures) Or 3.50 x 10 2 (indicates three significant figures)

16. How many significant figures are in each number? 0.0035 two significant figures 1.080 four significant figures 2371 four significant figures 1 dozen = 12unlimited significant figures 100.00 five significant figures 100,000 ambiguous

17. Significant Figures in Calculations (Addition and Subtraction Rule) We round the intermediate answer (in blue) to one decimal place because the quantity with the fewest decimal places (4.8) has one decimal place. In addition or subtraction calculations, the result carries the same number of decimal places as the quantity carrying the fewest decimal places.

18. Significant Figures in Calculations (Multiplication and Division Rule) The intermediate result (in blue) is rounded to two significant figures to reflect the least precisely known factor (0.10), which has ONLY two significant figures.