To determine the density of a metal sample using a graduated cylinder, here is how the metal should be placed and two possible sources of error with suggestions for minimizing them:
Placement of Metal Sample in the Graduated Cylinder
- Fill the graduated cylinder with enough water to fully cover the metal sample.
- Carefully tilt the graduated cylinder and slowly slide the metal sample down the inside wall of the cylinder. Do not drop or toss the metal in as this can cause splashing or even break the cylinder.
- Ensure the metal is completely submerged in the water without touching the sides or bottom in a way that could affect the reading.
- Record the initial volume of the water and the new volume with the metal submerged. The difference gives the volume of the metal.
Two Possible Sources of Error and How to Minimize Them
- Inaccurate Volume Measurements (Parallax Error or Graduated Cylinder Precision)
- The graduated cylinder readings can be off if viewed at an angle or if the cylinder increments are not precise.
- Minimize by always reading the water level at eye level and noting the meniscus at the bottom of the water curve.
- Use a graduated cylinder with smaller increments for better precision.
- Air Bubbles on Metal Surface
- Air bubbles can cling to the metal surface, artificially increasing the measured volume.
- Minimize by gently tapping or swirling the cylinder to dislodge bubbles or using a wetting agent if appropriate.
- Ensure the sample is slowly lowered into the water to avoid trapping air.
Additional tips:
- Handle the metal sample gently to avoid splashing or breaking the cylinder.
- Repeat volume measurements and take an average for accuracy.
These techniques help minimize error due to improper sample placement or inaccurate volume readings in density determination labs using water displacement with a graduated cylinder.
