1. Volume determination and density
Lab 3

2. Reading a Meniscus
Meniscus and Parallax

3. Reading and Recording Volumes
We use significant figures to indicate the accuracy and precision of glassware.
Significant figures for graduated glassware are determined differently from those of non-graduated glassware.
You will need to correctly apply the following rules every time you read a volume from glassware, or use a volume in a calculation, in order to appropriately incorporate the precision of the volume into the calculation.

4. Significant Figures: Volumetric Glassware
Use the tolerance table on p. 94 to determine glassware tolerance, unless it is printed on the glassware.
For example:
The 50 mL volumetric flask has a tolerance of ± 0.05 mL. Whenever you use your 50 mL volumetric flask, you will always report two zeros after the decimal, i.e mL.

5. Volumetric Flask
When this volumetric flask is filled to the calibration mark, what volume should be reported?

6. Volumetric Pipet
When this pipet is used to dispense solution, what volume should be reported?

7. Volumetric Pipet
When this pipet is used to dispense solution, what volume should be reported? And to which line should the pipet be filled?

8. Significant Figures: Graduated Glassware
Look at the glassware in question.
Find the smallest graduation.
Report your volume to the closest 10% of the smallest graduation.

9. Reading Graduated Glassware

10. Reading Graduated Glassware

11. Reading Graduated Glassware

12. Reading Graduated Glassware

13. Reading Graduated Glassware

14. Reading Graduated Glassware

15. Smallest Graduation A. Calculate major graduation – major graduation
B. Determine the number of spaces between two major graduations
Smallest Graduation = A / B

16. Reading Graduated Cylinders
What volume should be reported?

17. Reading Graduated Cylinders
Smallest graduation: 0.2 mL
10% value: 0.02 mL
Volume to the closest 10% of the SG:
6.62 mL

18. Reading Graduated Cylinders
What volume should be reported?

19. Reading Graduated Cylinders
Smallest graduation: 5 mL
10% value: 0.5 mL
Volume to the closest 10% of the SG:
293.5 mL

20. Reading Graduated Cylinders
What volume should be reported?

21. Reading Graduated Cylinders
Smallest graduation: 0.5 mL
10% value: 0.05 mL
Volume to the closest 10% of the SG:
11.50 mL

22. Reading Burets
What volume should be reported?

23. Reading Burets Smallest graduation: 0.1 mL 10% value: 0.01 mL
Volume to the closest 10% of the SG:
41.15 mL

24. Reading Burets
What volume should be reported?

25. Reading Burets Smallest graduation: 0.1 mL 10% value: 0.01 mL
Volume to the closest 10% of the SG:
15.48 mL

26. Balances
All sample/solution preparation should be performed at your station. Balances (and related counter space) should be used for weighing only!

27. Density Mass of a substance per unit volume. Units for today is g/mL.
Density changes with changing temperature.
As a result, volume changes (but mass stays constant unless you spill).

28. Mathematical Treatment of Data
% Error = x 100%

29. Example of Volume Calculation
Dry mass of a 50 mL beaker: g
Exactly mL of water is transferred from a 10 mL graduated cylinder into a 50 mL beaker.
Mass of the 50 mL beaker with mL of water: g
Mass of 10 mL water:
9.9856g
Volume read:
10.00 mL (why 2 digits of precision?)

30. Example of Volume Calculation
Water temperature:
21.2 ºC
Density at this temperature (p. 96):
g/mL
Volume Calculation:

31. % Error Calculation

32. Safety Concerns Reagent: Health Considerations: Food coloring
Avoid contact with skin and eyes.
Do not inhale vapor or spray.
Do not ingest.

33. Lab 4 Reminder
Complete and submit your pre-lab questions by the deadline.
Study for the next quiz.
Submit your Lab 3 Report at the start of next week’s lab.

34. Use these rules for “Volume Read”
Graduated Glassware
Look at the glassware
Find the smallest division (graduation)
Report volume to 10% of the smallest division
Volumetric Glassware
Find the glassware tolerance on the glassware or in Table 3.1
Report as many zeros after the decimal point for your volume, as digits after the decimal in the tolerance