Intro to Chem lab Equipment Weighing –Pan and analytical scales Liquid measure –Use of...
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Transcript of Intro to Chem lab Equipment Weighing –Pan and analytical scales Liquid measure –Use of...
Intro to Chem lab Equipment• Weighing
– Pan and analytical scales
• Liquid measure– Use of glassware, liquid meniscus
• Bunsen Burner– Construction, adjustments, lighting
• Safety hardware– Eyewash fountain, fire blanket & extinguisher
Utility Pan-Scale
• Resolution 0.010 gram• Maximum ≈ 1000 gram• For routine lab work• “good enough” for most
purposes• “Tare” feature useful• Simply switch on• NO chemicals on pan,
use dish or paper
Analytical Scale
• 0.0001 gm resolution• Maximum ≈ 200 gram• For critical measure• Sensitive to breezes• Sensitive to heat• “Tare” feature• Use tweezers • Fingerprints can matter• NO chemicals on pan
Individual vs. Cumulative weighing
• Weigh empty vessel• Tare Scale (m=0)• Weigh 1st item, record• Re-Tare (optional)• Remove 1st item• Weigh 2nd item, record• Repeat as required• Each is independent• Errors effect only one
• Weigh empty vessel• Tare Scale (m=0)• Weigh 1st item, record• Weigh 2nd item, record• Weigh 3rd item, record• Repeat as required• Differences = item mass• Saves time• Cumulative error issue
Reading Volume on Glassware
• Glassware calibrated to read at lowest part of surface “meniscus”
• Surface tension pulls liquid up side of glass
• Smaller diameters are more accurate, less volume per increment
• This example ≈ 6.7 ml
Burner Adjustments
• Wheel on bottom controls amount of gas– More gas when “unscrews” counterclockwise
• Upper collar controls air flow– Most air when slots are fully open
• Adjust 2 together for needed flow, best mix– 2-color light& dark blue flame is optimum
Lighting the Burner
• “Scratcher” is common welder’s ignition tool
• Press flint to abrader then squeeze handle
• Tilting burner helps• Use one burner to light
another, easiest way• Ask for help !
Counter-top utilities
• Electrical– 120 volt household with GFI
protection– Network outlet
• Natural Gas– Gas is “ON” with handle
parallel to hose
• Water– Tap water at desktops, for
cooling (not chem use)– Distilled water at back of
room, gray plastic tap
• Vacuum– Next to gas, for speedy
filtration
Fume Hoods
• Stinky stuff goes here !• Keeps experiment
smells out of classroom• Computer controlled,
more air with greater opening … noisier too
• Sliding door is also a splatter shield.
Ice Maker
• Near Weighing Room• Cooling baths for various
experiments• NO FOOD storage here.• NOT a good idea to eat
chemistry lab ice, could be contaminated !
Fire Extinguishers
• Red canisters on wall• Powder smothers fire
– “ABC” mix inside– Messy but effective
• Pull pin out, squeeze trigger to release pressurized contents
• Single-use, powder clogs release valve
• Pressure gauge should be in “green”
Fire Blanket
• Used to put out clothing fires.
• Designed to smother fire, excludes oxygen
• Don’t become the smoking filling of a fire-blanket burrito !
Safety Goggles Required!Goggles offer protection from gas, liquid, solid
Safety glasses only deflect flying objects
Eyewash Fountain & Shower
• Don’t experiment with it!• No drain, will flood lab
– May have a 15 min timer
• A conflict of regulations– Must have eye fountain– Spill might be hazardous– No drain avoids sewer
system contamination.
• NO fun here– Cold water, naked
students, wet floor!
• Emergency use only
Chem Lab Oven
• General drying – Experiment samples– Wet glassware
• Usually set at 110oC• Need to label which
sample is yours, they all look alike
Broken Glass Container
• Cardboard box in lab• Chipped, cracked, or
broke glass goes here• Do NOT use broken
or cracked glassware, could be dangerous
• Minor chips may be repairable, show your instructor if in doubt.
Hazardous Materials, NFPA-704 DiamondSymbol in white for specifics (radioactive, don’t use water, etc.)
Firemen might NOT enter area with danger value >2
Safety First!
• Have a GREAT semester in Chemistry!
• SAFETY FIRST is our #1 priority
• Bad examples follow – Possible candidates for “Darwin award”, for
elimination of the unfit.– “don’t do these at home”