In science, observations are made to discover, learn, and understand what’s going on in nature. In a science course, hands-on activities (experiments!) are the best way to make observations and learn science.
The Next Generation Science Standards (NGSS) describes 8 science and engineering practices that are essential for students to learn:
Ask questions.
Develop and use models.
Plan and carry out investigations.
Use math and computational thinking.
Construct explanations and engage in arguments from evidence.
Evaluate information.
Define problems and design solutions.
Communicate information.
Performing experiments in a science lab provides the experimenter (the student) the opportunity to learn, develop, and engage in many of these science and engineering practices, like a scientist.
So, the laboratory is a very important part of each course. Lectures and labs will be coordinated so you will be able to relate what you do in lab to what you do in lecture and vice versa. Experiments will demonstrate and elucidate concepts discussed in lecture. You will learn and apply chemistry lab techniques and develop skills to make observations and collect data, analyze data using the appropriate theory to obtain results, and interpret results to draw conclusions.
In the general chemistry lab, you will learn basic chemistry lab techniques and be introduced to chemistry equipment, instruments, and chemicals to make quantitative measurements, heat and cool substances, separate mixtures, and identify pure substances.
In the organic chemistry lab, you will learn basic organic chemistry macroscale and microscale lab techniques to separate, purify, and isolate organic substances, and characterization techniques to identify these substances. You will also gain an awareness of the nature of substances and their proper use and handling to make a safe lab environment.
Safety in the Chemistry Lab, Lab Procedures, and Lab Safety Agreement
“Why You Need to Wear Safety Glasses” (from Periodic Videos)
Runaway Hot Plates – it really happens!
A Visual Guide to Chemistry Glassware (from Compound Interest)
Some General Chemistry Lab Equipment (pictures)
“PPE Lab Experiences Worth Sharing” from Flinn Scientific
PPE Lab Experiences Worth Sharing
Use Real-Life Stories to Help Students Stay Safe
It can be difficult to convince students to use proper personal protective equipment (PPE) in the laboratory. Even with rules, safety contracts, reminders, and warnings, getting students to wear PPE is a challenge. As a chemistry instructor, one approach that I found helpful was to share true stories of incidents that could have been worse without the use of PPE.
Goggles: The Projectile Pencil Story
In most labs at my university, mine included, it’s a rule that goggles stay on—not just until your experiment is finished—but until you leave the lab. Because my students followed that rule, a freak accident that did not involve chemicals or glassware was prevented.
This story sounds unbelievable, but it actually happened. Two of my undergraduate students had finished their lab work and were cleaning up, goggles still on. One of the students accidentally dropped a pencil that landed eraser first on the floor and bounced up, rocketing directly toward her lab mate’s eyes. Fortunately, the “on target” pencil point hit the goggle lens, preventing injury. Without hesitation, my TA announced, “And that, people, is why we wear goggles!” After that, the TA never had to remind that class to wear their goggles again—it was 100% goggles on! Retelling the story of this unrepeatable, random event has helped me convey the importance of wearing goggles until you leave the lab because you have to be prepared for unexpected events. One lab group may be finished, but as long as students are still working, goggles must remain on for protection from splashed chemicals, shattered glass, and other “unexpected” projectiles.
Lab Coats: The Flaming Ethanol Story
Keeping your clothing clean is not the main reason for wearing a lab coat, as this story makes clear.
Requiring gloves and lab coats depends on the experiment and the regulations of each specific lab environment. If there is ever a spill or a fire, gloves and lab coats are a protective barrier between your students and injury. When I was in graduate school one of my lab mates spilled some ethanol near a Bunsen burner. Some splashed up and hit his lab coat which immediately started on fire. He quickly removed his coat and stomped out the flames without injury. Had he not been wearing a coat the outcome surely would have been worse.
Closed-toed Shoes: The Falling Scalpel Story
Considering the popularity of flip-flop sandals, this is an important safety message. One of my colleagues at Flinn shared this story to illustrate why shoes don’t have to be steel-toed to be PPE.
Students commonly forget to wear the proper shoes to lab because they often don’t see why shoes should matter. When it comes to using sharp instruments or glassware in the lab, closed-toed shoes are essential. Once in a biology class during a dissection, a student knocked a scalpel off the lab bench. The scalpel cut through the shoe and lodged there, point first. Because the student was wearing closed-toed shoes the scalpel caused no injury.
Use Personal, Positive Experiences to Support Safety Rules
In my teaching, sharing personal experiences of minor incidents that could have been worse without the use of PPE has helped students attend to their own safety and that of their lab mates. What stories do you and your colleagues have about accidents that were avoided thanks to PPE? Sharing those stories with students may help change their perspective regarding the value of protective equipment and makes it easier to enforce your lab safety rules.
Best Regards,
Megan Leifker
Senior Staff Scientist
Microwave Assisted Organic Reactions
“The microwave oven is the Bunsen burner of the 21st century.”
- Ajay Bose, microwave chemistry researcher (http://cen.acs.org/articles/90/i39/Chemists-Crank-Heat-Microwaves.html)
General Use of a Microwave Oven:
Don’t operate an empty microwave oven.
Keep the microwave oven clean. Clean up any spills in the oven.
Do not use metals in the microwave oven.
No sealed containers in the microwave oven. Sealed containers may explode.
Microwave ovens provide intense heating and can replace a long reflux.
Microwaves work by dielectric polarization. This means substances with a non-zero dielectric constant absorb microwave
radiation.
Questions:
1. What is dielectric constant?
2. Name two solvents with a non-zero dielectric constant. Give the dielectric constant of each solvent.
3. Does glass heat up in a microwave oven?
Use polar solvents only, e.g., water, acids, alcohols, and amides.
Polar solvents usually have –OH bonds, which absorb microwave radiation.
Good solvents: methanol, ethanol, isopropanol, 1-butanol, ethylene glycol
Medium solvents: water, acetonitrile, acetone, ethyl acetate, tetrahydrofuran (THF), dimethyl formamide (DMF)
Poor solvents: chloroform, dichloromethane, CCl4, hexane, toluene, xylene
Questions:
1. How is dielectric constant related to polarity?
2. What makes a solvent a “good” solvent for a microwave reaction? Identify at least two properties of a good solvent.
3. “Be careful using volatile solvents.” Why?
A commercial microwave oven has a frequency of 2.45 GHz.
This gives a microwave penetration depth of approximately 2 cm.
Question:
1. Based on the microwave penetration depth, what lab container size should you use for a microwave reaction?
To perform organic reactions in a microwave oven, remember glass does not heat up in microwave and will condense vapor (like a reflux condenser). For your reaction vessel,
a. use a test tube.
b. Attach a condenser to your test tube.
c. If you can’t use a test tube, use a beaker.
d. Important: Place a beaker or flask with water in the microwave with your reaction container.
Questions:
1. Should you seal your reaction vessel? Give reasons.
2. What Power Level or Setting on the microwave oven should you use for a “good” microwave solvent? Give reasons.
3. What Power Level or Setting on the microwave oven should you use for a volatile solvent? Give reasons.
4. How long should you run your reaction in a microwave oven?
Scientific Measurement and Significant Figures
Critical and Analytical Thinking in Science: Data Analysis
Science is a collaborative endeavor. Employers value employees who know how to work as a team. In lab, you will work in a group of 2 or 3. When you work in a larger group, assign a team leader, communicator, record keeper, and counselor for each lab and rotate roles for each lab. Each role is described in "Group and Collaborative Work". Make sure each team member contributes equally to each lab activity.
Group and Collaborative Work
The ability to work with people is an important skill that many employers value. A good group or team is able to share their diverse experiences, knowledge, abilities, and opinions to work effectively and efficiently to accomplish goals that one person may not be able to do as well or as quickly. Group or teamwork means members work together in a non-competitive, collaborative atmosphere. Skills include listening to others, being assertive with your input but not dominating the whole group, and taking responsibility for your role on the team and making sure other members are doing their role. It helps to focus on the “big picture”, i.e., the overall goal of the group, rather than getting caught up in individual issues.
For most of the labs, you will work in a group of four. Working in a larger group requires teamwork and communication. Each group member will be assigned one of the following roles so that duties are shared equally:
Group Leader: responsible for supervising the group and makes sure each member contributes equally to the team.
Communicator: responsible for communicating with the instructor and for completing all materials to be submitted by the team that reflects the thinking of all team members.
Record Keeper: responsible for keeping records of all materials discussed and is for informing absent team members of work missed and progress made.
Counselor: responsible for making sure all members of the team agree on planning, execution, and presentation of work.
Roles should be rotated with each different lab so each member of the group has the opportunity to
perform a different function.