Usefulness of Plastic Hoffman Apparatus in Chemistry Classes: A Case Study of Its Implementation with High School Teachers

doi:10.4236/ce.2013.47064

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Creative Education

2013. Vol.4, No.7, 446-451

Published Online July 2013 in SciRes (http://www.scirp.org/journal/ce) http://dx.doi.org/10.4236/ce.2013.47064

446

Usefulness of Plastic Hoffman Apparatus in Chemistry Classes: A

Case Study of Its Implementation with High School Teachers

Muhamad Hugerat*, Ahmad Basheer, Naji Kortam

SALiS Center, The Academic Arab College for Education, 22 Hachashmal St., Haifa, Israel

Email: *[email protected]

Received April 12th, 2013; revised May 13th, 2013; accepted May 22nd, 2013

mons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, pro-

vided the original work is p roperly cited.

In this article we present simple and feasible idea to introduce electrolysis experiments using accessible

materials in the classroom. We use plastic syringes and pipettes to build different shapes of Hoffman ap-

paratus for electrolysis. This activity was introduced to a group of 20 teachers from the Arab sector in Is-

rael to examine their impressions about the activity and investigate the feasibility of implementing the ac-

tivity in their classrooms.

Keywords: Electrolysis Workshop; Professional Development of Teachers; Case Study; Accessible

Materials; Plastic Apparatus

Introduction

Professional development of educators at different levels is

described by many researchers as a central lever leading to

change and improve the capabilities and achievements of the

education system (Scandholtz & Scribner, 2006).

Elliote (1999) emphasizes that it is very important to carry-

out local studies, and case studies to examine the interaction be-

tween local and global dimensions related to the development

of teachers.

Teachers can act as powerful mediators in introducing

change. Their decision to implement a new project depends on

their satisfaction from the current situation and their expecta-

tions from the contribution of the project in improving their tea-

ching (Wallace & Louden, 1998; Zidani, Kortam, & Hugerat,

2003).

In order to introduce a change, the teacher, himself, must go

through a learning process (Wheeler et al., 1995). In this proc-

ess, the teacher is an active partner in the creation of change.

This involvement is a constructivist teaching model, which is

essential in the introduction of such process.

In a study among elementary school teachers in Israel, Ben-

Chaim et al. (1994) found that training workshops encourage

the implementation of approaches, attitudes and scientific—

technological—and social literacy among the participating tea-

chers.

In this article we present simple and feasible idea to intro-

duce the microscale electrolysis experiments using accessible

materials in the classroom. We use plastic syringes and pipettes

to build different shapes of Hoffman apparatus for electrolysis.

We introduce this activity for high school teachers and we ex-

amine the impact of this implementation.

Starting from the last century, electrolysis of water solutions

has been widely demonstrated to students in secondary schools,

or in a first-year college in order to illustrate oxidation-reduc-

tion reactions as well as to demonstrate the use of an external

source of energy for driving non-spontaneous chemical reac-

tions (Hendricks & Williams, 1982; Hugerat, 2006, 2008; Hu-

gerat et al., 2009; Shakhashiri, 1992; Zhou, 1996).

A Hofmann apparatus is an apparatus for electrolyzing water,

invented by August Wilhelm von Hofmann. It consists of three

joined upright cylinders, usually glass. The inner cylinder is

open at the top to allow the addition of water and an ionic com-

pound, such as a small amount of sodium sulfate, to improve

conductivity. A platinum electrode is placed inside the bottom

of each of the two outer cylinders, connected to the positive and

negative terminals of a source of electricity. Gaseous oxygen

forms at the anode and gaseous hydrogen forms at the cathode

when a current runs through the Hofmann’s apparatus. Each gas

displaces water and collects at the top of the two outer tubes

(Hugerat, 2006, 2008; Hugerat & Schwarz, 2008; Hugerat et al.,

2009; Zhou et al., 2005).

Microscale chemistry is the reduction of chemicals use to the

lowest level at which experiments can be effectively performed.

It offers a safer way to perform chemical experiments by using

smaller quan tities of chem icals. Micros cale experiments are con-

ducted without compromising the quality or standard of chemi-

cal applications in educational institutions and the experimental

industry. The Benefits of Microscale Chemistry are: reduces

chemicals use by promoting waste reduction at the source; im-

proves laboratory safety (air quality, reduced exposure, and

spills); saves money; decreases experiment time; teaches stu-

dent s alternatives to conventi onal chemi s try (Singh et al., 1999;

Zhou et al., 2005).

For microscaling, the “Hoffmann Apparatus” the container,

the electrodes, the electrolyte, and the power supply are replac-

ed by smaller units; uses narrow 3-mL test tubes, insulated cop-

per wire (for the anode they are combined with a pencil lead),

diluted sodium hydroxide solution, or sodium sulfate solution

*Corresponding author.

M. HUGERAT ET AL.

with drops of universal indicator is introduced as neutral elec-

trolyte. A cheap AC/DC adaptor or a 9-Volt battery is used as

power supply (Hugerat, 2006, 2008; Hugerat et al., 2009; Hu-

gerat & Schwarz, 2008; Zhou et al., 2005).

Methodology

The workshop is one of the good ways to expose teachers to

innovations in building new devices on chemistry experiments.

It also opens new horizons for teachers to be more creative in

the construction of their own devices to use disposable materi-

als that have no adverse impact on the environment (Thompson

& Soyibo, 2002). The general idea behind this article is to in-

vestigate the effect of implementing the activity “Plastic Huff-

man Apparatuses” with teacher participants in the Academic

Arab College for Education in Israel. The main idea of the

workshop is to expose simple activity for electrolysis, such as

“plastic Hoffman apparatus” for teachers and to encourage tea-

chers to be active and creative in building their apparatuses.

The workshop for teachers took place in the laboratory of the

Academic Arab College for Education in Israel during Decem-

ber 2011.

The workshop consisted of four meetings of eight contact

hours each. During the workshop, selected topics in electrolysis

were introduced (Table 1). The main topic was electrolysis

through the implementation of an activity titled “Plastic Huff-

man Apparatuses”.

The participants in the workshop were 20 teachers from the

Arab sector in Israel; public and private high schools. Their par-

ticipation in the workshop was mandatory; they were selected

from different schools by the science inspector. They earned

hours toward their recertification.

The activity was presented in a full day (4 days) session of

eight hours (every day) in which the participants were intro-

duced to the concept of electrolysis and different methodologies

designed to enhance their content knowledge about the topic

and the pedagogical content knowledge to implement this topic

in their classrooms. The last two meeting focused on the useful-

ness of plastic Huffman apparatuses for electrolysis (Table 1).

The last meeting in the workshop focused on the creativity of

teachers, the teachers were asked to build thei r own plastic Huff-

man apparatuses using plastic and disposables materials.

This activity was introduced to a group of 20 teachers to col-

lect their impressions about the activity and investigate the fea-

sibility of implementing the activity in their classrooms. Fol-

lowing the activity, the researchers presented the participants

with a paper survey to collect their impressions about the activ-

ity, their previous knowledge about the topic of electrolysis and

their predictions of the benefits to their students through the

implementation of this activity in their classrooms.

Table 1.

Syllabus of the course o f the workshop.

Type of presentation Topics Hours

Lecture and Demonstration Introduction to Electrolysis 8

Demonstration and Active

Experimentation

Conventional Huffman

Apparatuses

Demonstration and Active

Experimentation

Plastic Huffman

Apparatuses

Creative and Active Experimentation

Creativity: Design of Plastic

Huffman Appa ratuses

The following represents the series of experiments imple-

mented during the activity.

Plastic Hoffman Apparatuses for Electrolysis

Advantages of doing these demonstrations:

 Students are encouraged to experiment and develop their

own electrolysis experience. Experiments can be done qui-

ckly.

 The creativity of students will be stimulated: They can find

individual solutions for a given problem. Their independ-

ence increases.

 Micro-scale saves time. It leaves more opportunities for

conversation, reflection and evaluation while protecting the

environment by using small amounts of chemicals: fewer

chemicals, less waste (less is more).

 Micro-scale saves money: special laboratory materials are

replaced by disposable items commonly found in daily life,

or easily acquired.

 Increasing sensitivity to the environment: becoming aware

of problems related to consumption, recycling and raw ma-

terials used in daily life.

Plastic Syringe Hoffman

Materials and chemicals

Two 5-ml plastic syringe, wooden test tube stand, bottom of

a disposable plastic cup container, two blunted hypodermic nee-

dles as electrodes, 2 insulated copper wires with crocodile clips,

9 V battery, sodium sulphate solution in red cabbage extract.

1. Connect the two plastic syringes from the bottom as

shown in Figures 1 and 2.

2. Pierce the disposable plastic cup container on the wooden

stand from the downside with the two blunted needles.

3. Totally fill the two plastic syringes with the electrolyte

(sodium sulphate solution in red cabbage extract).

4. Carefully turn the bottles upwards down and place them

tightly on the needles.

5. Add 5 ml of the electrolyte solution to the disposable plas-

tic cup container.

Figure 1.

Scheme of the pla stic Huf fman apparatus.

M. HUGERAT ET AL.

Figure 2.

Plastic Syringe Huffman apparatus experim ent.

6. Connect the needles acting as electrodes to the power sup-

ply (9 V battery).

Hazards

Although the power source (9 V battery) used is relatively

weak, electrodes should not be handled while cells are operat-

ing. Care should be exercised when testing the hydrogen gas

with a burning splint, be care ful of explosive hydrogen and oxy -

gen mixtures. Handle the sodium sulfate with care; they can

cause skin irritation. Wear gloves and goggles throughout the

experiments. Be careful during your work with the sharp nee-

dles, we suggest to cut the narrow part of the needle.

Observations and Explanations. Electrolysis of water is a

key chemical reaction, which is very often demonstrated for

students. When an electrical current (DC) is passed through a

water solution, oxygen gas and hydrogen ions are produced at

the anode while hydrogen gas and hydroxide ions are released

at the cathode side; see the equations (Hendricks & Williams,

1982; Hugerat, 2006; Shakhashiri, 1992; Zhou, 1996).

Cathodic Reduction:

 

2aq2 g

4H O4e4OH2H



 

 

2aq2 g

2H O4HO4e





Anodic Oxidation:

Redox Reaction:

  

22g 2gaqaq

The plant pigments presents in red cabbage, anthocyanin,

turn to red in acidic solutions, purple in neutral solutions, and

green to yellow in basic solutions. It can be clearly observed

after a few minutes of electrolysis that the color of the indicator

turns as the following (Figure 2):

6H O2HO4H4OH





Anode:

euple red

Cathode:

euplegreen

The intensity of the color depends on the change in the pH of

the solution near the electrodes. As a result of electrolysis of

water, bubbles of hydrogen gas as well as hydroxide ions ac-

cumulate in the cathode side. On the other hand, bubbles of

oxygen gas and also hydrogen ions are produced in the anode

side, and the volume ratio is 2:1 (H2/O2) (Figure 2).

Microscale Electrolysis in Two 3-ml Plastic Pipettes

In this experiment the two half-cells are two 3-ml plastic pi-

pettes (Figure 3), pierced by two injection needles, which have

been closed before by heating and compressing their plastic

ends. The pipettes are completely filled with a concentrated so-

dium sulfate solution in a red cabbage extract and placed into a

50-ml plastic cub with an electrolyte. This plastic cub acts as a

salt bridge and as a stand (Figure 3). A 9-Volt battery is used

as power supply.

Observations and Explanations

1. The indicator changes its colour to green in the cathode

pipette; and to red in the anode pipette.

2. Two gases develop in a volume ratio 2 (cathode) to 1 (an-

ode).

3. A fascinateur phenomenon can be demonstrated when the

DC connections between both electrodes is reversed. Due to re-

versing the polarity of both electrodes. The initially anode be-

come the cathode and the initially cathode is converted to anode.

As a consequence of this change, acid-base neutralization oc-

curs in the surrounding of each electrode due to the electrolysis

of water. After changing the polarity equal volumes of gases

Figure 3.

Two 3-ml plastic pipettes electrolysis experiment.

448

M. HUGERAT ET AL.

are formed in both pipettes.

4. After piercing the pipette heads with small closed hypo-

dermic needles these gases can be ignited by the spark of a

piezoelectric device: Fixing the pipette during the reaction re-

sults in a strong reduction of the gas volume. Water synthesis

of oxyhydrogen gas in the pipette head. As the reactants disap-

pear and the product is a liquid the volume is reduced very

much.

 

22 2

2HO2H O l

Electrolysis in One Pipette

In this experiment the cell is 3-ml plastic pipette, pierced by

two injection needles, which have been closed before by heat-

ing and compressing their plastic ends, the two injection nee-

dles acting as electrodes. The pipette is completely filled with a

concentrated sodium sulfate solution in a red cabbage extract

and placed into one hole of a plastic 6-well plate; the end of the

long tail of the plastic pipette dipped inside an another hole of

the plastic 6-well plate which contain soap solution (Figure 4).

A 9-Volt battery is used as power supply.

Observations and Explanations. When an electrical current

(DC) is passed through a water solution, oxygen gas is produc-

ed at the anode while hydrogen gas produced at the cathode.

These gases transferred through the long tail of the pipette to

arrive to the soap solution and we observed bubbles over the

soap solution. A simple method to check these gases (hydrogen

and oxygen) is to bring a source of fire to the bubbles; immedi-

ately a weak sound of explosion is heard. This is a safety ex-

periment because the amount of hydrogen and oxygen which

we produced during the electrolysis are very small.

Educational Component

20 school teachers participated in this workshop doing this

activity. Following the activity, the researchers presented the

participants with a paper survey to examine their impressions

about the activity, their previous knowledge about the topic of

electrolysis and their predictions of the benefits to their students

through the implementation of this activity in their classrooms.

Figure 4.

Electrolysis in one pipette in 6-well plate.

Some of the results from the analysis of the survey are:

1. Regarding previous knowledge about electrolysis, the ma-

jority of them stated that they gained this knowledge through

formal education. And they have no idea about new develop-

ments about new apparatuses from the new science education

journals, especially apparatuses from disposables materials such

as plastic apparatuses.

2. When the teachers were asked if they taught electrolysis in

their cla ssrooms, the majority stated that they teach electrolysi s

using conventional methods. Some of them wrote that they us-

ed conventional Hoffman apparatus.

3. When they were asked to describe briefly whether the ex-

periments presented in this workshop has helped them to un-

derstand the process of electrolysis in a better way. Most of

them have answered that after the activity the concept of elec-

trolysis became much clearer for them and that they can explain

it to audiences clearly. As an anecdotal remark, one of the tea-

chers stated that at the beginning of the workshop she had a

very little knowledge on the subject, and doing these experi-

ments has enlightened her about the topic and how to present it

to her students. Most of the participants concluded that using

these electrolysis experiments would allow their students to vi-

sualize what occurs during electrolysis. In the same manner,

teachers commented that the experiments were presented in

such a way that it is easy to implement and does not need a

science laboratory. Some of them also expressed a clear gain in

content knowledge using specific language to explain what

occurred in the electrolysis, such as the production of acid/base

in the anode/cathode and the liberation of O2 and H2.

4. When they were asked about the accessibility to dispos-

able materials to implement the activity, the teachers believe

that using disposable materials and a natural indicator such as

red cabbage juice makes the experiments simpler, so they can

think about other materials that they can use and if they do not

have all the materials, they will be able to find a way to obtain

them or provide alternate materials with which the experiment

can be performed. Figure 5 shows an experiment which was

In the last part of the workshop, as we noted at the beginning

was the important part which teachers were asked to design

new equipment apparatus. As seen in the experiment (Figure 5)

one the teacher built very simple experimental equipment ap-

paratus for electrolysis. He took a syringe and used two needle

electrodes, a battery of nine-volt current source, coffee cup as a

stand and salt bridge and followed the electrolysis of tap water.

As shown in this electrolysis device, he collected in the syringe

oxygen and hydrogen gas. The teacher tested for oxygen and

hydrogen when used with a match, the test is very safe because

Figure 5.

Plastic syringe apparatus for electrolysis designed by a participating

teacher in the workshop.

M. HUGERAT ET AL.

of the small amount of gas generated. The teacher could also

give an explanation for the product has a greenish yellow color

(which is chlorine) and the solid brown is rust. More creative

experiments using plastic materials were designed by other tea-

chers in the workshop.

5. When they were asked about the possibility to implement

this activity in the next academic year, the teachers expressed

their intentions to implement some of these electrolysis activi-

ties in their classroom.

6. The teachers believe that these activities will enhance the

learning process in their classroom, claiming that today most of

their students are visual learners and this kind of activity will

motivate and engage them in the learning process of these con-

cepts and wil l encourage them to do resea rch in the future.

7. When they were asked to express the main reasons that

would motivate them to implement this activity in their class-

room, the participants stated in general that:

 This activity is very simple and the materials are accessible.

We can think about other accessible and disposable materi-

als that were presented in this workshop by the researchers.

 The experiments can be carried out quickly. Our student

can repeat these activities in any place, such as home, be-

cause the materials are accessible, disposable, simple and it

is so easy to design such appa ratus.

 The students will be engaged and will feel part of the dis-

covery process and they can easily design their own appa-

ratus.

 The creativity of the students will definitively be simulated.

Analysis of teachers’ statements that came from a paper sur-

vey to check their impressions about the activity has detected a

range of professional descriptions reflecting changes in cogni-

tive, pedagogical and emotional dimension, on the one hand,

and various dilemmas, fears and doubts on the other.

The substantial improvement in the ability of teachers shows

the high skill of teachers to process appropriate activities for

students while going up a “step” in their professional develop-

ment. The study findings indicate that, during the course, the

teachers went through an evolutionary and professional change

expressed in a transition from scientific evidence of their spe-

cial field of knowledge, the type of experiments and materials

they used and the conceptualization of all this, to the acquisi-

tion and implementation of work methods, other ways of deal-

ing and thinking, in a different approach. The findings also in-

dicate that there was progress in their will and ability to deal

with the development and processing of materials originating in

the spirit of this approach. Teachers indicated that they gained,

as a result of the course, self-confidence and high skill of lo-

cating and processing other topics in chemistry that can be

combined during experiments with materials available and not

expensive.

The change that occurred in the perception of teachers as a

result of the course can be attributed to two factors combined

together. The first is raising teachers’ awareness of the need

and importance of processing such experiments; and the second,

the way teachers were exposed as learners of events during the

course in the context of Hoffman apparatus for electrolysis im-

proved their skills and abilities to the possibility of future de-

velopment of experiments and similar activities.

Some teachers are found in the midst of change process re-

flected in the fact that they are implementing teaching appro-

aches and content in real and not easy manner, caught between

the school reality that does not always allow making real change,

and the desire to change. The real “test” of change in the atti-

tude of teachers will be the implementation in the coming years.

Awareness of the need for change and its nature already exists,

based on the teachers’ statements and the way they began to re-

alize it, as reflected in the findings of this study.

After the significant developmental change expressed by

many teachers following their planning, implementation and

evaluation, it appears that, among teachers, a rise in the motiva-

tion to change was observed; in addition to recognizing the

importance and profound understanding of the entire process. A

possible outcome of teacher development at this stage will be

the involvement of school teaching teams, where they function

as agents of change to their colleagues. Continuation of the pro-

cess of teacher development depends on the teacher himself, on

the school support and the offered academic accompaniment.

Conclusion

The implementation of these activities with teachers from

high school, and the analysis of the data collected from the

participants corroborate the position of this paper. Although

electrolysis can be a difficult subject to teach and perform ex-

periments (given the common lack of resources available to

teachers in high schools), teachers are motivated to experiment

with and introduce these approaches in their classrooms and,

with it, the content knowledge of the subject. The presented

simple and familiar apparatus should make these experiments

safely available at all levels in chemistry classes. Teachers that

have conducted the aforementioned described experiments with

plastic Hoffman apparatus have shown excitement and fun es-

pecially when observing visually occurring electrolysis. We be-

lieve that these workshops motivate the teachers to be more

creative in designing new apparatuses in teaching and learning

chemistry, and encouraging their students to be more active

learning and creative in their classes.

The research described in this paper, has clear implications

for action at school. This action depends on several factors,

where teachers constitute the central link in the success. Expec-

tations to make a real and comprehensive scientific change in

the education system depend largely on the ability of profes-

sional development of teachers to lead real change in the class-

room.

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