The Science Teacher

The Science Teacher
September 2005, p. 24-29
Habits of Mind for the Science Laboratory

Lisa Hayes, Margaret Smith, and Charles Eick

Laboratory experiences should be an integral part of any high school science program, especially laboratory activities designed so that students gather data, explore concepts, and answer questions through inquiry (NRC 1996, p. 23). While conducting inquiry investigations, every science teacher must properly instruct, supervise, and maintain equipment and materials to ensure student safety in the laboratory. A number of cases exist in which students were inadvertently harmed due to a teacher’s negligence in the laboratory (Figure 1).

Figure 1. Cases in the news.
“A Connecticut high school teacher substituted mercuric oxide for silver oxide in an experiment. Twenty-two students working in pairs heated 1.75 g over a Bunsen burner for 15 minutes. After massing the heated material the teacher realized that the mercury was being vaporized and the students were evacuated. Three days after the incident, testing of the students revealed eight of them had elevated mercury in their urine. Three months later one student still had elevated mercury levels” (CDC 1988).
“A student received minor facial injuries when she added concentrated sulfuric acid to a wet test tube provided by her lab partner. The contents boiled out of the tube and struck her in the face. Her lab partner had not dried the tube as instructed” (Young 2000).
“A 14-year-old boy put potassium dichromate in a bottle of soda two students were sharing in a physical science lab. The two students became seriously ill and were rushed to a hospital” (Kingsley 1999).
“A 17-year-old…was electrocuted during a 1997 classroom science experiment in the 3,600-student Franklin County, Ga., school district. The experiment involved stringing a wire around the classroom and cutting away insulation at several points so students could attach probes from a voltmeter to learn how to measure electricity” (Hoff 2003).

According to the Council of State Science Supervisors, negligence is defined as “conduct that falls below a standard of care established by a law or profession to protect others from an unreasonable risk of harm or the failure to exercise due care” (CSSS, p. 2). So, how can science teachers avoid negligence and minimize the risk of accidents when preparing for, instructing, and supervising students before, during, and after lab? Cultivating the following “habits of mind” at each stage of laboratory work is the first big step toward achieving safety in the laboratory setting.

Habits of mind before the lab

Lab safety begins with the teacher. Teachers must make learning how to be safe an integral and important part of their professional development and work. Teachers who are unfamiliar with laboratory instruction should take whatever steps necessary to prepare for the unique challenges associated with safety in conducting laboratory investigations and demonstrations. Attending workshops and conferences, along with researching safe laboratory practices, can provide a foundation for understanding and implementing safe laboratory guidelines and procedures.

Developing an atmosphere of “safety first” is perhaps the most important aspect of establishing the habit of mind for lab safety. The following suggestions will help lay down the foundation for a safe laboratory climate. The teacher should

·  instruct students using a clear set of laboratory safety rules, procedures, and penalties before ever going to lab (Figure 2);

·  document evidence of instruction on safety guidelines through lesson plans, safety posters in lab, student assessment, and parental/student signatures on easily read and understood safety contracts (Figure 3); and

·  document student attendance for safety instruction, providing instruction at a later time for any absent students.

Figure 2. Laboratory safety rules. (Adapted from the safety contract that Flinn Scientific publishes for public use online at www.flinnsci.com.)
Introduction and purpose
Science offers “hands-on” laboratory experiences. You will be doing many lab activities that require the use of chemicals and equipment that can potentially be hazardous. In this class, Safety is the #1 priority! To ensure a safe working environment for everyone, you must adhere to the following safety guidelines at all times.
I. General guidelines
A. Follow all instructions carefully.
B. Never work alone in the lab.
C. Never touch equipment, chemicals, or other materials without permission.
D. No food, drinks, gum, or candy in the lab.
E. Perform only authorized experiments.
F. Be on your best behavior in lab—no horseplay, practical jokes, or pranks!
G. Keep your work area clean and tidy at all times.
H. Know the location of and how to use lab safety equipment.
I. Always be alert to potential hazards and work cautiously in the lab.
J. Dispose of chemicals according to the teacher’s directions. No solids in the sink! Put nothing in the sink without consulting your teacher.
K. Read all labels carefully before using chemicals.
L. Keep your hands away from face, mouth, eyes, and body during experiments and wash them before you leave the lab.
M. Clean, rinse, and dry all equipment and return it to its proper place.
N. Never leave your lab station unattended!
II. Clothing
A. Chemical splash goggles and aprons must be worn during all laboratory experiments.
B. Inform the teacher if you wear contacts.
C. Dress appropriately for lab—wear closed-toe shoes, tie hair back, remove rings and watches, and do not wear loose clothing.
III. Accidents and injuries
A. Report ALL accidents to your teacher immediately—even the small ones!
B. Chemicals in the eye should be flushed with tepid water from the eyewash for 15—20 minutes.
C. Chemicals on the skin should be washed with soap and water, or in the case of a large-scale spill the safety shower should be used.
IV. Handling chemicals
A. Consider all chemicals dangerous—do not touch, taste, or smell without specific instructions. Use the wafting technique when testing for odor.
B. Check labels twice before using a chemical. Take only the amount you need.
C. Never return unused chemicals to their original container.
D. When using concentrated acids and bases, practice extreme caution. Add acid to water when diluting concentrated acids.
E. Do not use flammable materials near open flames.
F. Be very careful when carrying chemicals around the room.
V. Handling glassware and equipment
A. Never handle broken glass with bare hands. Notify the teacher if you break something.
B. Broken glass is only disposed of in the broken glass container—never in the regular trash.
C. Be careful using electrical equipment—make sure plugs and cords are in good condition and that your hands are dry.
D. Check glassware before use and report any chips or cracks.
E. Use the correct equipment for the task.
F. Use safety equipment when handling heated equipment and do not place hot glass directly on the lab table or under cold water.
VI. Heating substances
A. Follow all instructions and safety precautions when using a gas burner.
B. Never leave a lit burner unattended.
C. Direct substances being heated away from yourself or anyone else.
D. Use insulating materials or tongs when handling heated equipment.
E. Do not place hot equipment on the lab table—use an insulating pad or wire gauze.
F. Do not place hot equipment on a balance—let it cool first!
Figure 3. Laboratory safety contract.
I, ______, have read and agree to follow all of the safety rules set forth in this contract. I realize that I must obey these rules to insure my own safety, and that of my fellow students and instructors. I will cooperate to the fullest extent with my instructor and fellow students to maintain a safe lab environment. I will also closely follow the oral and written instructions provided by the instructor. I am aware that any violation of this safety contract that results in unsafe conduct in the laboratory or misbehavior on my part may result in being removed from the laboratory, detention, receiving a failing grade, referral to the office, and/or dismissal from future labs.
______
Student Signature
______
Date
Dear Parent/Guardian:
We feel that you should be informed regarding the school’s effort to create and maintain a safe science classroom/laboratory environment. With the cooperation of the instructors, parents, and students, a safety instruction program can eliminate, prevent, and correct possible hazards.
You should be aware of the safety instruction your son/daughter will receive before engaging in any laboratory work. Please read the list of safety rules your child received. No student will be permitted to perform laboratory activities unless this agreement is signed by both the parent/guardian and the student and is on file with the teacher.
Your signature on this contract indicates that you have read the Safety Rules and Contract and are aware of the measures taken to insure the safety of your son/daughter in the science laboratory, and will instruct your son/daughter to uphold his/her agreement to follow these rules and procedures in the laboratory.
______
Parent/Guardian Signature
______
Date

Science teachers must continually have safety on their minds before going to each and every lab. Instructing students in proper lab safety is not a “one-shot” deal. Teachers must again document and provide clear instructions regarding specific laboratory procedures and specific safety issues pertaining to each lab activity. Teachers may wish to model certain equipment setups or techniques for students if a portion of a lab activity is particularly difficult or requires observing a technique beforehand. Prelab quizzes are also an effective tool to determine if students are prepared for a particular lab and have read both the safety precautions and lab procedure (Figure 4).

Figure 4. Prelab quiz.
Chemistry prelab quiz Name ______
Hydrated crystals Block ______Date ______
Guiding question: What is the formula of hydrated magnesium sulfate (Epsom salts)?
Background: Hydrates are compounds that incorporate water molecules in their crystalline structures. The ratio of moles of water to one mole of the anhydrous compound is a small, whole number.
Answer the following questions—you may use examples to explain calculations.
1. What safety precautions must be observed when lighting and using a gas burner?
2. How will you experimentally obtain the mass of water and the mass of the anhydrous magnesium sulfate in the hydrate?
3. How will you convert your experimental masses to moles?
4. How will you determine the formula for the hydrated form of the magnesium sulfate?
5. If, when you are heating your hydrated magnesium sulfate, your crucible cracks or falls off the ring stand, what will you do?
Answer Key
1. What safety precautions must be observed when lighting and using a gas burner?
Long hair should be pulled back and loose clothing secured; do not wear dangling jewelry; make sure no flammable materials are in the area; cotton clothing is preferred; do not leave lit burner unattended; turn off gas as soon as you are through using the burner. Before lighting, be sure to know how to adjust the burner’s flame and how to turn it off quickly.
2. How will you experimentally obtain the mass of water and the mass of the anhydrous magnesium sulfate in the hydrate?
Determine the initial mass of the hydrated Epsom salts. After heating, determine the mass of the anhydrous compound. The difference between the two masses is the amount of water driven off of the hydrate.
3. How will you convert your experimental masses to moles?
Determine the molar mass of each compound. Use this to convert from mass (in grams) to moles.
4. How will you determine the formula for the hydrated form of the magnesium sulfate?
Divide the number of moles water by the number of moles of the anhydrous compound. This will give the experimental number of moles of water relative to the magnesium sulfate.
5. If, when you are heating your hydrated magnesium sulfate, your crucible cracks or falls off the ring stand, what will you do?
Immediately turn off the gas. Do not touch the crucible! Notify your teacher at once.

Habits of mind when considering a lab

Figure 5. A typical lab activity, then and now.
Guiding question: Can you experimentally identify the freezing point of a substance?
Traditional, less safe method: Graphing latent heat of fusion of naphthalene
Safety issues: Moderately toxic organic chemical and skin irritant; requires good ventilation in use; use of Bunsen burner flame
Put naphthalene crystals in a test tube. Place a thermometer in the naphthalene. Heat gently with a Bunsen burner until the naphthalene has melted. Stir the naphthalene gently with the thermometer while it is cooling and record the temperature every 15 seconds for about 7 minutes. Plot a graph of temperature versus time.
Alternative, safer method: Graphing latent heat of fusion of water
Safety issues: Safe chemicals (salt, water) and no Bunsen burner flame or heat
Place 5 mL of water into a test tube. Place a thermometer in the water. Place ice cubes, salt, and water into a 400 mL beaker. Lower the test tube into the ice-water bath. Stir the water in the tube gently with the thermometer while it is cooling and record the temperature every 15 seconds for about 15 minutes. Plot the graph of temperature versus time. Note that you must continue to stir and maintain the ice-water bath for the entire time.

Science teachers must have a strong understanding of the potential hazards of performing laboratory procedures and the use of equipment or chemicals before conducting a lab with students. Many concepts explored in lab can be done with considerably smaller amounts of chemicals (microscale), very dilute solutions, or inherently safer materials. Science teachers should always ask themselves, “Can we teach this concept another way in the lab?” or “Do the risks associated with this activity outweigh any potential learning outcomes?” Teachers should consider the following points before choosing a lab activity: