Laboratory Laboratory Hardware Part Hardware Part IIIIII

Bioscience, Equipment UnitHot/ Stir Plate and Balances

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BellworkBellwork

When you go to the doctor for a physical, what type of scale is used to get your weight? Do you know how they use the scale and if so please describe?

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ObjectivesObjectives1. Use hot plates/stirrers2. Understand how to identify,

select, and use laboratory balances

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TerminologyTerminology

Hot plateStir PlateZero/ Tare

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HeatingHeating   What type of stove do you have at

home? Is your stove type similar to any lab equipment you have used? If so describe if not then describe your stove burner and how you control it?

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Lab bench heating in the Lab bench heating in the LabLab

There are two common ways to heat a reaction or a piece of glassware in the lab:

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With an Electric Hot Plate

With a gas Bunsen Burner

Think-Pair-Share Think-Pair-Share Considering the Bunsen Burner and the Hot Plate which would be preferable for use in a Biosciences lab? Give at least two reasons for your choice.

If you are stuck try to consider safety and convenience when formulating your answer.

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The Hot PlateThe Hot PlateThe standard for lab top heating.Safer than a Bunsen Burner when using flammable solventNo need for gas lineMany have built in digital temp gaugesControlled with a dial.Many are dual Hot and Stir plates.

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Using The Hot PlateUsing The Hot Plate1. Plug in and pre-heat to desired

temperature (if digitally controlled)2. Place solution to be heated on hot plate

with a thermometer in it (even if there is a digital temperature readout on hot plate).

3. Heat for desired period of time.*It may be necessary to cover solution with para-film to help keep volume constant

4. Turn plate off but do not unplug until “Surface Hot” light goes out.

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Stir PlateStir PlateUsed to automatically stir a solution by way of a magnetic stir bar.

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The magnetic stir bar is placed in the beaker with the solution to be stirred.

Using a Stir PlateUsing a Stir Plate

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Once the glassware to be stirred is on the stir plate, plug it in.

Slowly increase the speed of the stirrer until desired speed is reach, a controlled whirlpool.

If splashing occurs lower speed dial

Finger FlashFinger FlashWhen finished using a hot plate:I.Unplug immediately and so as not to leave on accidently

II.Unplug only after “Surface hot” light turns off

III.Unplug only if the plate is cool to the touch

Show the correct number of fingers for the appropriate response

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Balances and ScalesBalances and Scales

Manual Balances:

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Electronic Balance/ Scale

Electronic BalanceElectronic BalanceSimilar to the balance used to get your weight in the doctor office.Digital balance generally will report weights in metric (mg, g, and kg) and in imperial (oz, and lbs.)

Which unit will we be using in the lab and why ?

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Our Electronic BalanceOur Electronic BalanceMost common balance in a lab:Gram scales “tens place”:

0.0g to +500.0g Milligram scales “thousands place”:

0.000g to +100.000g

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We have _________ balance in our lab

Which Electronic BalanceWhich Electronic Balance Should Be Used Should Be Used

On a slate indicate which balance should be used and in less than 12 words why?

Lisa needs to weigh out 2.225g of substance A

John needs to weight out 100.0g of substance B

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Using a Digital BalanceUsing a Digital BalanceWe will fill out an SOP then you will practice in the lab. Safety:Never push down on the scale weigh platformDo not weigh liquid unless told to do so.

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Digital Balance SOPDigital Balance SOP1. Insure balance is plugged in and set to

metric units. If you need to change this touch the “Units” button.

2. Direct weighing: determining the mass of something.

a. Touch the “Zero” or “Tare” button and wait until the balance read only zeros. Now carefully place the object on the balance and wait for numbers to stop changing before recording mass and units

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Digital Balance SOP Cont. Digital Balance SOP Cont. II

3. Dispensing a particular mass : determining the mass of something.

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a) Use weight paper/ boat or glassware directly on weigh platform.

b) Touch the “Zero” or “Tare” button and wait until the balance read only zeros.

c) Weigh out desired amount into weight paper/ boat or glassware using a scoopula or spatula.

Digital Balance SOP Cont. Digital Balance SOP Cont. 11114. Clean balance and box with brush to remove

any spills.Trouble shooting:If scale gives error message or flashes try

turning power off to balance and then back on.

If error message is present when weighing heavy glassware or large quantities of substance insure you are not over the balances limit.

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Lab Practice: Using a Digital Lab Practice: Using a Digital BalanceBalance

You will be using your Digital Balance SOP to complete the mini lab at your lab station.Work as a group to complete parts A, B, and C.

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ClosureClosureLetter to a Friend

On a ½ sheet of scratch paper write a short letter 2-3 sentences explaining how to use a digital balance

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