We took advantage of the gap in AP testing to work through Lesson 82. The Lesson 82 Worksheet called for students to work in groups to prepare salt solutions and then we measured the specific gravity of each solution using a hydrometer. Our class results are provided below:
Period 2 Results:
| Want 500 mL total volume (water = solvent) | |||||
| Group | grams of salt | Specific Gravity | Volume (L) | moles of salt | M |
| 0 | 0 | 1.000 | 0.5 | 0.00 | 0.00 |
| 7 | 2.9 | 1.004 | 0.5 | 0.05 | 0.10 |
| 1 | 8.75 | 1.012 | 0.5 | 0.15 | 0.30 |
| 2 | 11.7 | 1.014 | 0.5 | 0.20 | 0.40 |
| 5 | 17.5 | 1.026 | 0.5 | 0.30 | 0.60 |
| 6 | 23.4 | 1.034 | 0.5 | 0.40 | 0.80 |
| 3 | 29.25 | 1.042 | 0.5 | 0.50 | 1.00 |
| 4 | 35.05 | 1.048 | 0.5 | 0.60 | 1.20 |
| 8 | 43.85 | 1.052 | 0.5 | 0.75 | 1.50 |
Period 3 Results:
| Want 500 mL total volume (water = solvent) | |||||
| Group | grams of salt | Specific Gravity | Volume (L) | moles of salt | M |
| 0 | 0 | 1.000 | 0.5 | 0.00 | 0.00 |
| 7 | 2.9 | 1.002 | 0.5 | 0.05 | 0.10 |
| 1 | 8.75 | 1.010 | 0.5 | 0.15 | 0.30 |
| 2 | 11.7 | 1.014 | 0.5 | 0.20 | 0.40 |
| 5 | 17.5 | 1.024 | 0.5 | 0.30 | 0.60 |
| 6 | 23.4 | 1.030 | 0.5 | 0.40 | 0.80 |
| 3 | 29.25 | 1.042 | 0.5 | 0.50 | 1.00 |
| 4 | 35.05 | 1.050 | 0.5 | 0.60 | 1.20 |
| 8 | 43.85 | 1.062 | 0.5 | 0.75 | 1.50 |
For reference, the Lesson 82 PowerPoint is available for download.
Additionally, students are encouraged to practice observing the relationship between moles, volume, and molarity using the University of Colorado Molarity PhET simulation below:
https://phet.colorado.edu/sims/html/molarity/latest/molarity_en.html
The Art of Science 