Micropipette Lab

Comparing Precision and Accuracy!

Cornell Notes & INB’s

S - Set up the paper

T - Take Notes

A - After class process the notes3 summary statements1 questions

R - Reflect / review

Q column:1. Students write

questions from notes

2. Everything in this column should be a question

Precision

The precision of a measurement describes the “units” used to measure something

The smaller the unit, the more precise!

Example of Precision

QuickTime™ and a decompressor

are needed to see this picture.

QuickTime™ and a decompressor

are needed to see this picture.

“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

Which tool can measure volume more precisely?

QuickTime™ and a decompressor

are needed to see this picture.

QuickTime™ and a decompressor

are needed to see this picture.

10 ml, 50 ml, or 100 ml graduated cylinder?

20µL =.020 ml

How aboutcompared tothis tool?

Accuracy

The difference between your measurement and the “accepted” value

The bigger the difference, the less accurate you were!

Examples of Accuracy

QuickTime™ and a decompressor

are needed to see this picture.

= 3.7854118 liters= 1 gallonThese are accepted values

Bob measured this container of milkAnd determined that it is 5.5 gallons

Bob wasn’t very accurate!

Maria measured this container of milkAnd determined that it is 1.1 gallon

Maria was very accurate!

Mai measured this container of milkAnd determined that it is 3.7854118Liters

Mai was accurate and precise!

Rules for using a micropipettor: o Gently remove the disposable t ips with your f ingers. o Never use the micropipettor without a t ip. This could cause damage to the instrument. o Never lay a loaded pipette down or til t it s ideways because this could allow liquid to run back into the instrument. o Never let the button snap back into place. Always allow it to ri se slowly back into posit ion.

Rules for using a micropipettor: o Gently remove the disposable t ips with your f ingers. o Never use the micropipettor without a t ip. This could cause damage to the instrument. o Never lay a loaded pipette down or til t it s ideways because this could allow liquid to run back into the instrument. o Never let the button snap back into place. Always allow it to ri se slowly back into posit ion.

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

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

QuickTime™ and a decompressor

are needed to see this picture.

Precision