1. Micropipette Lab Comparing Precision and Accuracy!

2. Cornell Notes & INB’s S - Set up the paper T - Take Notes A - After class process the notes 3 summary statements 1 questions R - Reflect / review Q column: 1.Students write questions from notes 2.Everything in this column should be a question

3. Precision The precision of a measurement describes the “units” used to measure something The smaller the unit, the more precise!

4. Example of Precision “The pencil is a little over 9 cm” “The pencil is a little over 95 millimeters Ruler #1 can measure in centimeters Ruler #2 can measure in millimeters Which ruler is more precise??? Ruler #2

5. Which tool can measure volume more precisely? 10 ml, 50 ml, or 100 ml graduated cylinder? 20µL =.020 ml How about compared to this tool?

6. Accuracy The difference between your measurement and the “accepted” value The bigger the difference, the less accurate you were!

7. Examples of Accuracy = 3.7854118 liters = 1 gallon These are accepted values Bob measured this container of milk And determined that it is 5.5 gallons Bob wasn’t very accurate! Maria measured this container of milk And determined that it is 1.1 gallon Maria was very accurate! Mai measured this container of milk And determined that it is 3.7854118 Liters Mai was accurate and precise!

8. Rules when using a micropipette Gently remove the disposable tip by depressing the button (not the top) Never use a micropipette without a tip Never lay a loaded pipette down or tilt it sideways because this could allow liquid to run back into the instrument Never let the button snap back into place, always allow it to rise slowly back into position

9. Let’s practice! Gently add a tip by pushing it onto the end of the pipette Slowly turn the top knob to set the desired measurement 200 is 200, 20 is 020 (large volume pipette) 20 is 200, 2 is 020 (small volume pipette) Slowly depress top knob down until you reach the “first stop” Slowly put tip of pipette into water and slowly release knob Depress top knob until you reach to “second stop” to release liquid

10. Precisio n