Date
________________________
Objectives:
1.
Demonstrate ability to follow lab
procedures accurately.
2.
Develop skills for measuring liquid
volumes with graduated cylinders.
3.
Follow safety procedures.
Safety:
-
Wear safety goggles at all times.
-
The liquids used in this lab can stain
clothing. Clean all spills
immediately. Do not drink or taste the liquid.
-
DO
NOT CROSS-CONTAMINATE any chemicals as this could cause a
dangerous reaction.
Procedures:
Preparation
1.
Fill a flask halfway with water.
a.
This will be used to rinse your graduated
cylinder, pipettes, and test tubes.
b.
All used rinse water should be disposed of
in the “Waste Bucket” located at each table.
2.
Place 6 CLEAN test tubes in a test tube rack and label them in order
A,B,C,D,E, and F.
3.
Locate three pipettes at your
station. They should be labeled
“Y” (yellow), “R” (red), and “B” (blue).
These pipettes should ONLY be
used to transfer the appropriate colored liquid.
4.
Rinse the graduated cylinder with water,
swirl, and pour wastewater into the waste bucket. Make sure to repeat this cleaning process between each measurement to
avoid contamination.
Part
A:
1.
Measure 25 mL of RED liquid and pour it
into test tube A.
2.
Measure 17mL of YELLOW liquid and pour it
into test tube C.
3.
Measure 21mL of BLUE liquid and pour it
into test tube E.
Part
B:
1.
From test tube C, measure 4 mL and pour
into test tube D.
2.
From test tube E, measure 7 mL and pour
into test tube D. Swirl gently.
3.
From test tube E, measure 4 mL and pour
into test tube F.
4.
From test tube A, measure 7 mL and pour
into test tube F. Swirl gently.
5.
From test tube A, measure 8 mL and pour
into test tube B.
6.
From test tube C, measure 3 mL and pour
into test tube B. Swirl gently.
7.
Obtain a score from your teacher before
continuing to Part C.
Part
C:
1.
Complete the data table below BEFORE
cleaning up.
2.
Measure the actual amount of liquid in
each tube before disposing in the waste container.
3.
Rinse all test tubes thoroughly and store
each one upside down in the test tube rack to dry.
Data:
Test
Tube
|
Description
of Liquid Color
|
Expected
Volume (mL)
|
Actual
Volume (mL)
|
A
|
|||
B
|
|||
C
|
|||
D
|
|||
E
|
|||
F
|
|||
TOTAL
Volume in Test Tubes A-F (mL)
|
|||
Conclusion Questions
1.
How
did your starting materials differ from your final product? Give
specific examples from the
lab.
2. What is cross-contamination and how can you prevent it from occurring?
3. Was any liquid spilled during the
lab? What could you do to prevent chemical spills in the future?
4. Describe and draw how to accurately read the volume of a liquid
in a graduated cylinder.
5. Scientists repeat experiments often and
find the average of many data points because there is ALWAYS some amount of experimental error in any experiment. Your goal in class is to minimize that
error as much as possible.
a. Calculate your percent error using the
following equation:
Total Expected - Total Actual
Percent
Error =
Total Expected
x 100
b. What can you do in the future to minimize experimental error?
