Lab 3

1
Lab 3

• Determination of Density
• of Liquids and Solids

2
Uncertainties in Scientific Measurement

• Systematic Errors (Determinate Errors)
• Bias an experimentally determined value in one
  direction
• Have a definite value and an assignable cause
• Influence experimental accuracy
• May be avoided altogether OR
  measured and
  corrected (correction factor)

3
Uncertainties in Scientific Measurement

• Random Errors (Indeterminate Errors)
• Errors may be high or low
• Arise from uncertainties in measurement that are
  either unknown or uncontrollable by the
  experimenter
• Effect experimental precision

4
Reducing Your Error (Mass measurements)

• Do not touch the object to be weighed with bare
  hands
• Clean the outside of object to be weighed (wipe
  wash dry), prior to weighing
• Tare the balance to avoid recording an irrelevant
  mass (e.g., the container)

5
Reducing Your Error(Volume Measurements)

• Carefully read volumes Avoid parallax error!
• Carefully transfer fluids (or an object into
  fluid) to avoid splashing tilt container
  containing the fluid for easier transfer
• Gently tap side of fluid container to dislodge
  air bubbles

6

• Parallax Error occurs when you read the
• volume anywhere BUT at the bottom of the
• meniscus (for most liquids) or top of the
• meniscus (for mercury).
• CORRECT (true)
• reading is at the
• meniscus (curve) in the
• center of the cylinder.

7
Actual Densities

• Rubbing alcohol and Rubber stopper correct
  densities will not be given
• Metal correct densities of all unknowns will be
  posted

8

• Remember significant figures!!!!
• Do problem and adjust (round) final answer.