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A Year Without
PROCEDURES Lisa Backus
Most high school chemistry labs contain detailed procedures on how to perform
experiments, collect data, and analyze findings. These step-by-step instructions
often eliminate opportunities for inquiry, higher levels of thinking, and the sense of
accomplishment students find through independent discovery.
For these reasons, two years ago I elected to remove
Removing procedures specifically outlined procedures from many chemistry labs
from chemistry labs in my classroom. By doing so, I promoted collaboration
between students as they designed their own steps and
creates opportunities illustrated that more than one way exists to solve a prob-
for student inquiry lem. I challenged students and let them experience the sci-
entific process and the reward of discovering answers on
their own. This article describes a chemistry-based experimental year without
procedures, but the concept can be applied to any scientific discipline.
54 The Science Teacher
Implementing inquiry
The opening lab
For Lab 1 (Figure 1), I gave students 16 substances—liquids,
solutions, and solids—and asked that they describe the
substances as thoroughly as possible, including differences
and similarities. I intentionally provided a variety of chemicals
that had different densities, colors, and odors, and that would
change colors, produce precipitates, bubble, or solidify when
mixed. This opening lab acted as a springboard for our unit
on how chemists identify unknowns.
In addition to visually observing the substances, students
chose to examine solubility in water, melting points, odor,
reactions in flames, and reactions with combining samples.
Students were required to check with me before doing any-
thing beyond visual observations and prior to disposal (I re-
quired a disposal check for each lab). If students needed sup-
plies or chemicals to examine substances, they had to ask for
these materials. I did not want to influence student choices
by setting out particular supplies, such as Bunsen burners.
After obtaining my safety approval, students who chose
to put materials in the flame were surprised when one
material turned red (strontium chloride) and others were
perplexed when they added water to a white powder and
it solidified (sodium polyacrylate). Several times during the
lab, students excitedly showed me their findings.
Over the next several labs, students proceeded to iden-
tify several of these 16 substances. To identify the first two,
aluminum and zinc, density was used. I decided that deter-
mining density (Lab 2, Figure 1) was a formal lab proce-
dure students could design on their own (Figure 2, p. 58).
Reviewing the procedures
Before introducing inquiry-based labs, I began by examining Designing density procedures
many of the current labs scheduled for our sophomore/junior Because most students already had some familiarity with
chemistry class. Could students be successful doing the lab density, removing the procedure created a need for them to
without the procedures? Did they have enough background make connections with prior knowledge (Figure 2). Discussions
information? Would it be safe? I found that many labs could centered on student recollection of the density formula: Was the
be done successfully without detailed procedures; summary formula mass divided by volume or volume divided by mass?
descriptions of these labs are provided in Figure 1 (p. 56). How should the volume of the metal pellets be measured?
To address safety, students were instructed at the begin- As students approached the problem, some groups tried
ning of the year on general chemical safety procedures and putting just the pellets in a graduated cylinder, but quickly
given a safety contract to read and sign. Prior to each lab, decided that the air between the particles was taking up
special reminders were given regarding specific chemicals; some of the volume. In the end, to determine the volume
however, because these chemicals and their uses could most students had success using water displacement in a
change based on students’ ideas, I required that all proce- range of containers and various amounts of material. The
dures be cleared with me before implementation. This pro- range of values obtained led to an informative post-lab dis-
cedure review gave me a chance to check for possible safety cussion on accuracy and precision in measurements.
issues and question student lab design, although I did not After finding the density, students were asked to identify
usually correct student procedures unless they were unsafe. their metal from a list of possibilities. I did not show them
Reviewing lab designs also kept me busy during lab peri- where to find this information; some students searched the
ods. Instead of providing and correcting procedures, I posed internet, while others looked in reference books.
questions or problems to solve, and left it up to students to
figure out the experimental steps. To develop procedures Determining heat of reaction
and conduct experiments, students typically brainstormed As the year progressed and topics became more novel, I
and worked in groups of four, although occasionally they had to make sure students received the proper background
worked in pairs and a couple of times as a whole class. information necessary for successful labs. Occasionally, prior
October 2005 55
FIGURE 1
Labs without procedures. Always wear safety goggles and
follow proper safety guidelines.
Lab Question/problem posed Chemicals* Background Student responses
information prior to lab
1 Describe as thoroughly as Al shot, vinegar, 1 M HCl, corn General science Characterized samples by
possible your unknown syrup, Zn shot, 1 M NaOH, experiences. Under- appearance, solubility in water,
chemicals. CaCO3(s), 0.1 M Na2SO4, 0.1 standing of laboratory odor, color, viscosity, density,
M BaCl2, CuSO4•5H2O (s), safety rules. reaction with each other, etc.
universal indicator, sodium
polyacrylate(s), citric acid(s),
SrCl2 (s), sand and distilled H2O
2 Identify your metal using Al shot and Zn shot from Most had some Most found volume by water
density (a list of possible above lab experience with density. displacement and mass on
choices are given). A a balance. Used handbook
detailed example of this lab of chemistry and physics or
is given in Figure 2 (p. 58). chemical dictionary to identify
metals using the density.
3 Which materials are soluble (NH4)2SO4, Ca(C2H3O2)2, CaCl2, General knowledge of Class discussed how much of
in water and are there any CoSO4, Cu(C2H3O2)2, MgSO4, KBr, solubility. each sample (same mass or
patterns? NaC2H3O2, Na2SO4, NaCl, SrCl2, volume), how much water, and
Ca(NO3)2, KNO3, LiNO3, CaCO3, how long to stir.
BaCO3, MnO2, CuCO3, CuO, ZnO
4 Identify the unknown solution Unknowns from first lab, 0.1 M Previous lab examined Students used precipitation
from a list of possibilities Na2SO4 or 0.1 M BaCl2 marked what chemicals formed reactions and results from
(NaCl, Na2SO4, Co(NO3)2, as letters precipitates when mixed.previous lab as a process of
Pb(NO3)2, K2CrO4, Na3PO4, [0.1 M of AgNO3, K2SO4, elimination. (Using spot plates
BaCl2, CuCl2, AgNO3). Ba(NO3)2, FeCl3, Na3PO4, NaCl] and microscale amounts makes
this more manageable.)
5 What products are formed NaHCO3 Students given a brief Students heated small amounts
when baking soda is heated? background on baking of baking soda and weighed
soda and three possible material afterwards. Discussions
equations. revolved around how much
Students had already baking soda to use, how long to
learned how to heat it, how it could be heated
solve mole-related safely, and how to perform
stoichiometry problems. calculations.
6 Determine how temperature KNO3 Previous labs involving Students debated how to keep
affects the solubility of solubility. uniform temperature and how
KNO3. to measure the amount of solid
that dissolved.
to conducting labs, I would assign related homework to give when I told them that such an instrument was not available.
students exposure to the knowledge needed. Often, though, For homework the night before the candle-wax lab, students
I used the lab to introduce new concepts that were then had been asked to find the definition of a calorie (students
further developed in class discussions following the lab. were already familiar with joules). The first successful group
For example, one lab involved having students determine decided to place water over the candle and measure the temp-
the amount of heat given off per gram of burning candle wax erature rise in order to calculate heat. This group was the first
(Lab 8, Figure 1). At first, students wanted to use some type to make the connection between their homework and the lab.
of meter that would measure heat directly and were puzzled Other lab groups developed similar procedures with
56 The Science Teacher
Lab Question/problem posed Chemicals* Background Student responses
information prior to lab
7 What is the concentration of 0.068 M CuSO4 Students previously Students made standards of
the copper sulfate solution? made and saved known concentration and
solutions of known compared the colors, others
concentrations (0.2 and evaporated their solution, and
0.1 M CuSO4). one group formed and weighed
a BaSO4 precipitate.
8 How much energy is A candle The night before this Students placed water over a
released per mole of candle lab, students were told flame and measured increase in
wax when it burns? to find the definition temperature and loss of candle
of a calorie. Previously, mass. Discussions centered on
students calculated heats how much water to use, how
of reaction from bond to place the water above the
energies and used joules. flame, and how to avoid heat
loss.
9 Determine and graph the None given Students had just done Students performed a variety of
quantitative gas relationship exploration involving tasks. They used balloons, flasks,
between one of these qualitative observations thermometer, syringes, and
pairs—P and V, V and T, of these variables. pressure gauges.
or P and T (keeping other
variables constant).
10 Calculate the heat of solution KNO3, CaCl2, NH4Cl, NaCl Students familiar with Students measured mass of solid,
for four different solids (J/g) heat being absorbed or placed it in water, and measured
released during reactions temperature change. Different
and changes of state. quantities were used. Too much
water or too little solid gave
small temperature changes.
11 Determine and measure two One solution labeled A with 0.02 Students were given a Students changed temperature,
factors that will affect the M KIO3 another solution labeled clock reaction to first degree of mixing, and
reaction rate. B with 4 g starch, 2 g NaHSO3, and observe before they concentration of one of the
5 ml of 1 M sulfuric acid per liter made changes. reactants.
12 What properties do acids 1 M HCl, 1 M HC2H3O2, 1 M Previous general Students remembered acid
have in common? What do NaOH, 1 M KOH, 6 M HCl, 6 M knowledge. litmus and pH paper tests,
bases have in common? Do HC2H3O2, 1 M NH4OH, 1 M H3PO4 reaction with metals, and
all acids react the same? reaction with baking soda.
* These were the chemicals given as part of the lab. For some of the labs students requested additional chemicals, depending on their
own procedures. Some of the most common chemicals requested are listed in italics in parentheses.
variations in the amount of water, the position of the water between two variables (P and T, T and V, or P and V).
above the flame, and the time the candle burned. Postlab For example, one group examining V and T put a
discussions focused on how to minimize heat “loss” to the thermometer inside a flask and a balloon on the top of the
environment, and how this affected the accuracy of the lab. flask. They varied the temperature by placing the flask in
Gas law labs were my personal favorites of the year (Lab the refrigerator and then into different hot water baths (the
9, Figure 1). Every group designed distinctly different pro- balloon was not submerged). At each temperature, volume
cedures. Students worked with ice, balloons, eudiometers, was measured as the combination of the volume of the flask
syringes, and pressure gauges to discover the relationship and the volume of the balloon (which students assumed to
October 2005 57
FIGURE 2 thoroughly data was recorded. After the student critiques,
Density inquiry lab without procedures I also assessed the notebooks. Students were usually very
honest and accurate with their comments.
example. (Taken from Figure 1, Lab 2). In addition to the lab notebook, students wrote lab
Editor’s note: Although various standard density lab procedures reports that included results, conclusions, and questions. I
are available (see online version of this article at www.nsta. often graded these myself. For some of the labs, students
org/highschool#journal for an example) students achieve a were assessed on accuracy (i.e., did they identify the un-
deeper understanding of the concept of density if they develop known?). In most cases, however, students demonstrated
a procedure on their own. understanding through designing successful procedures
and analyzing their results thoughtfully.
I. Introduction
The purpose of this lab is to identify two unknown elements Obstacles and rewards
(A and E) from their densities. As expected, the labs were not as efficient without
II. Investigation procedures. Many labs took more planning time. Labs
Decide how to determine the density of your materials. with defined procedures had been refined over the years to
You may discuss your plan in groups of four, but each lab take out all the “kinks.” By removing the procedures, I put
pair must analyze their own material. Before doing anything, many of the kinks back in, adding more time to the lab or
have the teacher OK your procedure for safety. Write your sometimes creating ambiguous results.
procedure in your lab notebook. Errors, however, led to great discussions on how to im-
prove the labs and insight on creating good lab procedures.
III. Data
For example, after discussing student errors with tempera-
Record your data in your lab notebook in an organized fashion.
ture in the rates of reaction lab, students repeated the ex-
IV. Results periment using their classmates’ suggestions. In hindsight,
Calculate the density of the material. Show your work in I wish I had done this for a few more of the labs (e.g., the
your lab report. candle wax lab and solubility with temperature). Students
V. Analysis questions were eager to make improvements and produce more
Record your responses in your lab report. meaningful results; I was surprised by this enthusiasm to
repeat a lab. By interpreting ambiguous results and refin-
a. From the list of possibilities, using reference materials,
ing experimental procedures, students achieved a much
determine the possible identity of your unknown. If possible, better understanding of the nature of science.
use other properties (e.g., color, luster) to help identify your Although there were instances of excitement and ac-
material. Defend your choice. What additional information complishment, there were also a few complaints. Some
would increase your confidence in your identification? students were initially frustrated when they discovered
b. Assuming you have correctly identified your material, that a day’s lab would have no procedure. However,
what is your percent error? Is your error small enough when surveyed at the end of the year, student feedback to
to give you confidence in your identification? labs without procedures was positive.
c. What could have contributed to the error? Finally, as I look back over the year, I realize that my
d. Examine your procedure. List all improvements you would students did not just simply learn more about chemistry.
make if you conducted the experiment. Despite occasional frustrations, and less efficient methods,
e. How is density important in everyday life? List as many students learned how to approach a new problem, brain-
applications as you can. storm ideas, create a plan of action, perform the tasks, criti-
cally analyze the findings, draw conclusions, make adapta-
be close to spherical). Afterward, students graphed results tions, and start again—and they did it themselves. ■
and even discovered information on absolute zero.
Lisa Backus is a science teacher at Deerfield High School, 1959 North
Assessment Waukegan Road, Deerfield, IL 60015; e-mail:lbackus@dist113.org.
During all of the experiments in Figure 1, students were
required to keep an accurate account of their analyses in a Caution!
lab notebook, including a table of contents, title, purpose,
individual procedures, and data. It is important to follow standard safety procedures and
Using this rubric, students swapped notebooks (not with appropriate disposal regulations when using chemicals and
their lab partner) and critiqued each others work, then lab equipment. This general overview is not intended to cover
critiqued their own. Criteria included the ease with which the specific safety precautions for each lab. Consult resources
someone could duplicate the student’s lab based only on the such as material safety data sheets, chemical texts, or reference
descriptions in the procedures, and how appropriately and books for more detailed information.
58 The Science Teacher
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