| 1. Statement of hypothesis |
Not required for this task |
| - Effect linked to variable |
|
| - Directionality of effect |
|
| - Expected effect/change |
|
| - Independent variable |
|
| - Dependent variable |
|
| 2. Procedures for investigation |
|
| - Detailed procedure/experimentally feasible |
Method includes details which will clearly result
in accurate determination of concentration of unknown, including
steps below and repeated trials. |
| - Sequence to plan |
Suggests method to determine molarity of unknown
solution |
| - General strategy |
First identifies unknown solution as an acid
or base using appropriate indicator, then suggests titration
using neutralizing solution. |
| - Safety procedures |
Safety goggles should be worn; care in handling
acids and bases. |
| - Use of equipment/diagram |
Appropriate equipment and materials are suggested,
especially use of burette and indicator. |
| 3. Plan for recording and organizing
observations/data |
|
| - Space for manipulation of data or qualitative
description |
Could include space for averaging data; stipulation
of indicator used. |
| - Matched to plan |
Plan is comprehensive so that all observations
and data generated by plan may be recorded; e.g., space for
repeated trials is included. |
| - Organized sequentially |
Organized so that recording follows data as
generated. |
| - Labelled fully (units included) |
All columns and rows are identified; correct
units of measurement are used. |
| - Variables identified |
Solution used to titrate unknown is indicated
as acid or base. |
| 4. Quality of observations/data |
|
| - Consistent data |
At least two trials are consistent with expectations. |
| - Accurate measurements, observations |
Measurements are +/- 3.0 mL |
| - Completed data table |
All trials performed and data recorded. |
| - Correct units |
Volumes labelled as mL or L. |
| - Qualitative description |
Indicator is identified. |
| 5. Graph |
Not required for this task. |
| - Curve is appropriate to data trend |
|
| - Points plotted accurately |
|
| - Appropriate scale |
|
| - Axes labelled with variabls |
|
| - Variables placed on correct axes |
|
| 6. Calculations |
|
| - Calculated accruately |
Calculations are complete and mathematically
correct. |
| - Substituted correctly into relationship |
Moles of neutralizing solution are used to find
molarity unknown solution. |
| - Relationship stated or implied |
Volume of neutralizing solution is converted
to moles. |
| - Units used correctly |
mL correctly converted to L. |
| - Use all data available |
Calculations are performed on all generated
data; reason stated if data is excluded. |
| 7. Conclusion |
|
| - Consistent with scientific principle |
Conclusion based on student's data is consistent
with identity and concentration of unknown solution. |
| - Sources of error |
* |
| - Consistent with data |
Unknown solution is identified as an acid or
a base and concentration is determined, based on student's
data.(1) |
| - Relationship among variables stated |
Unknown solution is neutralized by acid or base
used as titrating solution. |
| - Variables stated in conclusion |
Unknown and acid or base (neutralizing solution)
are mentioned here. |
* These elements were not scored in this task; a
"holistic" scoring approach was utilized so that the
other four elements had a total value of 5 points.
(1) Conclusion may not accurately reflect identity
or concentration of unknown solution, but if conclusion is a reasonable
reflection of student's work, a point should be given.
