Lab Techniques 101: Introducing Your Students to the Chemistry Lab
Product Manager, Chemistry & Inquiries in Science®
As you welcome your new crop of fresh-faced and eager chemistry students, you may find yourself haunted by the ghosts of chemistry labs past. Banish those memories of broken glassware, burner mishaps, buret accidents, and student bafflement upon hearing “Erlenmeyer flask.” Start your year off right with an overview of basic chemistry lab techniques.
Begin with a discussion of safety. Lab safety can be categorized into 3 areas: How Students Look, How Students Act, and How You Prepare. Stress to your students the importance of using personal protective equipment: eye protection, gloves, and aprons or lab coats. Emphasize the need to wear appropriate footwear and long pants and to tie back their long hair.
Make sure students understand that their actions in the lab have serious safety consequences. No eating or drinking and no horseplay are ever allowed.
Finally, your early preparation will ensure a safe year in the lab. Before students arrive, make sure that eyewashes and safety showers are in good working order and that chemicals are in good shape, labeled, and stored properly. Know ahead of time the hazards associated with all the activities you have planned for the year. A more exhaustive list of safety guidelines can be found at Lab Safety Do's and Don'ts.
Introduce your students early to the different types of laboratory glassware, how and when to use them, and how to care for them. Chemistry glassware is of 2 types: graduated and volumetric. A piece of graduated glassware is used to measure and dispense several different volumes, while a piece of volumetric glassware is used to measure and contain 1 specific volume.
Point out the differences in precision between different types of graduated glassware. For instance, beakers are marked with approximate volumes, while burets are marked more precisely. Describe or demonstrate glassware basics such as the use of 2 hands when transporting glassware (1 hand around the side and 1 hand underneath), the proper disposal of broken glass, and the careful tightening of clamps around glassware.
Finally, make sure students understand the importance of leaving clean glassware in great shape for the next class. Proper cleaning includes a warm water rinse, followed by a thorough wash with a glassware cleaning solution. Then students should rinse to remove all traces of detergent, finish with a final rinse using distilled water, and place the glassware on a drying rack. Stock your lab with an assortment of brushes to clean the different sizes of glassware.
Introduce students to the laboratory equipment before starting any experiments to prevent injury and streamline future activities. Many chemistry experiments require the addition of heat, and that often means using a burner. Proper lighting of a Bunsen burner includes these simple steps:
- After verifying that the tubing is in good condition, attach it to the gas supply and the burner.
- Make sure the air vents on the burner are closed, and turn on the gas.
- Hold a striker close to the top of the burner, and squeeze the striker to create a spark.
- Once the gas ignites, adjust the air vents to create a flame. The most efficient flame has a light blue outer cone and a bright blue inner cone. If there is any yellow in the flame, open the air vents to admit more oxygen.
Familiarize students with the basics of the electronic balance:
- Never place a chemical directly on the balance pan.
- Learn to zero the balance with a container before measuring the mass of a chemical.
- Remove any spilled solids on or around the balance with a soft brush.
A hot plate with a magnetic stirrer is a handy piece of equipment. Caution students against dropping the stir bar into a glass container. Demonstrate how to begin stirring at the lowest speed setting before increasing the speed to create a vortex in the liquid.
Teaching proper methodology not only yields more accurate results, but, by instilling confidence in your students, it makes working in the lab safer and more efficient. Here are a few basics to stress:
- Read the liquid level in glassware at the bottom of the meniscus.
- Test the odor of a chemical by wafting it toward the face; never directly smell a chemical.
- Learn to run liquids down a glass stirring rod when transferring them from 1 container to another.
- Never pipet directly from a reagent bottle; transfer a small amount to a beaker and then pipet from the beaker.
- It is not necessary to completely fill a buret to the 0-mL mark to begin a titration. Start at a comfortable eye level, note the starting volume, and then begin dispensing.
Have a safe and successful year in the lab!