Common Chemical Procedures
Chemistry/Science 9
Mr. Remenap
IT IS UNDERSTOOD THAT YOU HAVE SAFETY GOGGLES ON FOR ALL OF THE FOLLOWING PROCEDURES!!
1. Lighting a Bunsen or Tirrill Burner:
a. Obtain a burner from the appropriate cupboard.
b. Inspect the hose for cracks, breaks, leaks, or other possible flaws; replace as needed.
c. Attach the loose end of the hose to the gas outlet. Twist twice while pushing; more will get the burner stuck, less will allow gas to leak out.
d. Light a match safely.
e. Turn on the gas at the valve—on is parallel to the gas nozzle; off is perpendicular.
f. Gently touch the lit match to the top of the burner nozzle—this will ensure that the flame is lit at the base, and will not blow out.
g. Blow out the match; rinse with water; dispose in a trash can. DO NOT PLACE BURNT MATCHES IN THE SINK DRAINS.
2. Massing a Chemical, No vessel: Triple Beam Balance.
a. Set all of the balance’s sliders to zero. Check that the balance is at the balance point, or zeroed.
b. Add weigh paper, weigh boat, or other material on the balance pan.
c. Reset the balance using the adjustment screw until it reads zero.
d. Adjust the slider to the needed amount of chemical; for instance, if you 15 g of salt, move the 1’s slider to “5” and the 10’s slider to “10.”
e. Add chemical slowly until the balance again reads zero.
f. Do not put spilled chemicals back into the bottles; wipe up any spills. Reset the balance for the next group.
g. Wipe up any spills (as directed by your teacher) immediately.
3. Massing a Chemical, With Vessel: Triple Beam Balance.
a. Set all of the balance’s sliders to zero. Check that the balance is at the balance point, or zeroed.
b. Place the vessel to be massed on the pan.
c. Adjust the sliders until the balance again reads zero.
d. Note the correct mass of the vessel; you should be able to measure with some accuracy to the 1/100ths place.
e. Move the sliders further, to account for the needed mass of chemical, for instance: Vessel: 44.15 g; Need 5 g Salt: move 1’s slider 5 g.
f. Add chemical until the balance reads zero.
g. Wipe up any spills (as directed by your teacher) immediately.
4. Measuring Accurate Amounts of Liquid.
a. Use appropriate glassware: Graduated Cylinders are high accuracy; assume high accuracy needed here.
b. Place Graduated Cylinder on lab bench.
c. Fill a larger vessel with needed liquid—just slightly more than you will need.
d. Align your eyes with the line marking the correct amount of liquid on the Graduated Cylinder.
e. Pour the contents of the larger vessel into the Graduated Cylinder slowly.
f. Stop before the meniscus* reaches the appropriate line on the Graduated Cylinder.
g. Add drop by drop, using a glass rod, spatula, or dropper bottle as needed, until the appropriate amount is reached.
h. Wipe up any spills (as directed by your teacher) immediately.
5. Pouring Chemicals from one Vessel to Another.
a. Place empty vessel on lab bench, about 15-20 cm away from the edge of the bench (that’s roughly 5 inches). Avoid keeping your hand on this vessel for safety reasons.
b. GENTLY touch the lip of the full vessel to the lip of the empty vessel. This prevents filling to quickly, spilling, or “pouring down the side” of the full vessel.
c. Gently tip the full vessel to empty its contents, keeping the two vessels in constant contact.
d. Stop when the appropriate amount of liquid is measured.
e. Wipe up any spills (as directed by your teacher) immediately.
6. Chemical Disposal Techniques:
1. If your teacher directs that your chemical wastes be thrown in the trash, the following precautions should be followed:
a. Use Paper towel to transport any loose chemicals to the trash. Do not use your hands for safety’s sake.
b. Any chemicals in vessels may be transported directly to the trash and dumped. Obviously, do not throw away the vessel itself.
c. No liquids should be thrown in the trash, regardless of safety issues—it prevents unwanted messes for our custodial staff.
2. If your teacher directs that your chemical wastes be thrown down the drain, the following precautions should be followed:
a. If the material is liquid, pour slowly and carefully to avoid splashing. Pour directly over the drain area, so that when water is added as a rinse, there is no splashing of chemicals.
b. If the material is a solid, mix it with water (or another solvent, as directed by your teacher) to dissolve it, to prevent drains from backing up. Then follow the procedures for disposing a liquid.
3. If your teacher gives you specific instructions for disposing a particular danger, toxic, or noxious chemical, follow those instructions to the letter. There may be many reasons to dispose of chemicals in this way: risks to you, the environment, the school, or the other students.