Laboratory Hardware Part III Bioscience, Equipment Unit Hot/ Stir Plate and Balances 10/1/2015 1

Bellwork 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? 10/1/2015Property of CTE Joint Venture 2

Objectives 1. Use hot plates/stirrers 2. Understand how to identify, select, and use laboratory balances 10/1/2015Property of CTE Joint Venture 3

Terminology Hot plate Stir Plate Zero/ Tare 10/1/2015Property of CTE Joint Venture 4

Heating Heating 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? 10/1/2015Property of CTE Joint Venture 5

Lab bench heating in the Lab There are two common ways to heat a reaction or a piece of glassware in the lab: 10/1/2015Property of CTE Joint Venture 6 With an Electric Hot Plate With a gas Bunsen Burner

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. 10/1/2015Property of CTE Joint Venture 7 k

The Hot Plate The standard for lab top heating. Safer than a Bunsen Burner when using flammable solvent No need for gas line Many have built in digital temp gauges Controlled with a dial. Many are dual Hot and Stir plates. 10/1/2015Property of CTE Joint Venture 8

Using The Hot Plate 1. 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. 10/1/2015Property of CTE Joint Venture 9

Stir Plate Used to automatically stir a solution by way of a magnetic stir bar. 10/1/2015Property of CTE Joint Venture 10 The magnetic stir bar is placed in the beaker with the solution to be stirred.

Using a Stir Plate 10/1/2015Property of CTE Joint Venture 11 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 Flash When 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 10/1/2015 Property of CTE Joint Venture 12

Balances and Scales Manual Balances: 10/1/2015Property of CTE Joint Venture 13 Electronic Balance/ Scale

Electronic Balance Similar 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 ? 10/1/2015Property of CTE Joint Venture 14

Our Electronic Balance Most common balance in a lab: Gram scales “tens place”: 0.0g to g Milligram scales “thousands place”: 0.000g to g 10/1/2015Property of CTE Joint Venture 15 We have _________ balance in our lab

Which Electronic Balance 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 10/1/2015Property of CTE Joint Venture 16

Using a Digital Balance We will fill out an SOP then you will practice in the lab. Safety: Never push down on the scale weigh platform Do not weigh liquid unless told to do so. 10/1/2015Property of CTE Joint Venture 17

Digital Balance SOP 1. 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 10/1/2015Property of CTE Joint Venture 18

Digital Balance SOP Cont. I 3. Dispensing a particular mass : determining the mass of something. 10/1/2015Property of CTE Joint Venture 19 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 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. 10/1/2015Property of CTE Joint Venture 20

Lab Practice: Using a Digital Balance 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. 10/1/2015Property of CTE Joint Venture 21

Closure Letter to a Friend On a ½ sheet of scratch paper write a short letter 2-3 sentences explaining how to use a digital balance 10/1/2015Property of CTE Joint Venture 22