Senior Form Chemistry – Hydrogen Peroxide
Hydrogen Peroxide (H2O2)
Teacher’s Version
NOS/STSE Features
When we make decision on socio-scientific
issue, it is necessary to analyze the arguments
of a claim systematically to check whether
they are valid or not.
Table of Contents
Introduction
Activity 1: Bleaching shark’s fin with hydrogen peroxide
Part A: News reports about the danger of bleaching shark’s fin
with hydrogen peroxide
Part B: Seeking advice from reliable sources
Part C: Extension – Shark’s fin: Enjoy it or Ban it?
(i)
P.1
Activity 2: Studying the kinetics of decomposition of hydrogen peroxide
Activity 3: Should we drink hydrogen peroxide?
Part A: News reports for and against drinking hydrogen
peroxide to improve health
Part B: Extension: Alternative Medicine
Appendix 1: Reference for Activity 1 Part B
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Appendix 2: Lesson Plan
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© 2007 The University of Hong Kong – Faculty of Education. All rights reserved
Senior Form Chemistry – Hydrogen Peroxide
Introduction
Rationale
‘Reading to learn’ has been advocated for quite a long time. Reading forms a significant
part of students’ learning. Scientists devote much of their time to scrutinizing research
papers. For the general public, they receive much information through newspapers,
magazines, pamphlets and the Internet. Hence, training our students to read carefully and
critically, as part of the communicative skill, becomes essential – no matter whether we
want our students to be scientists or citizens who can make informed judgments based on
written sources of information. However, it has been found that teachers in general only
allocate a small part of their teaching sessions for students’ reading. Also, teaching
resources on reading, particularly those have local relevance, are scarce. In the light of
this, the materials suggested here aim at illustrating an example of how teachers can
make use of newspaper clippings in the classroom. This package is enriched by two
meaningful extensions which bring out the discussions of whether shark fin consumption
should be banned and the use of alternative medicine respectively.
Level of study
Number of lessons
Activity 1: Form 3 – Form 7
4 lessons (each lesson 40 – 50 minutes)
Activity 2: Form 6 – Form 7
Activity 3: Form 4 – Form 7
Contents
1. Comparison of different newspaper clippings’ reports on the issue “Bleaching
shark’s fin with hydrogen peroxide”
2. Kinetics of decomposition of hydrogen peroxide
3. Basic argument analysis tutorial
4. Analysis of the arguments extracted from different newspaper clippings about
harmfulness of hydrogen peroxide
Teaching package includes
Worksheets (Teacher’s Version and Student’s Version)
(i)
© 2007 The University of Hong Kong – Faculty of Education. All rights reserved.
Senior Form Chemistry – Hydrogen Peroxide
Activity 1
Bleaching shark’s fin with Hydrogen Peroxide
Part A - News reports about the danger of bleaching
shark’s fin with hydrogen peroxide
Part B - Seeking advice from reliable sources
Part C – Shark’s fin: Enjoy or Ban it? (Extension)
Part A – News reports about the danger of bleaching shark’s fin by
hydrogen peroxide
Notes: The two articles below are talking about the same issue: the problem of
bleaching shark’s fine with hydrogen peroxide. However, article one is a bit
misleading and unclear. This activity shows how a misleading article can adversely
affect students’ understanding of a scientific issue.
You will be divided into two groups to read two articles about bleaching shark’s fin
with hydrogen peroxide
Article One
Over-consumption can cause cancer and deform foetuses
Sing Tao Daily 2003-12-05
Guangdong government officials have discovered a factory using industrial grade hydrogen peroxide to treat
sharks fins. It might upset people to know that this delicacy is potentially carcinogenic.
A pharmacist and a doctor pointed out that industrial grade hydrogen peroxide is very concentrated. Also, it is
manufactured carelessly and may be mixed with quite large amounts of heavy metals and other toxins. They
may cause gastrointestinal ulcers if consumed. Medical literature has also pointed out that hydrogen peroxide
may cause cancer. If a pregnant woman takes the substance, she might give birth to a deformed fetus.
The colourless liquid may lead to stomach ulcers
Like water, hydrogen peroxide is a colourless liquid. It is used as a bleach, oxidizer or germicide in industry.
Industrial grade hydrogen peroxide has a high oxygen content. However, our body will accumulate toxic
substances from the industrial product after excessive use, which changes body cells and may even cause
cancer.
A doctor stated that if our body absorbs too much oxygen, it can damage cell membranes and speed up aging.
Hence, it is generally not recommended. But it is used by some naturopathic medicine specialists for treating
diseases.
Still toxic after boiling
Professor Lee Kwing-chin of The School of Pharmacy, CUHK indicated that diluted hydrogen peroxide
bleach is not very harmful to humans. However the concentration of industrial grade hydrogen peroxide is so
high that it may damage the digestive system. Also, prolonged absorption or massive absorption could cause
ulcer. He said that medical literature has indicated an association between hydrogen peroxide and cancer.
Legislator Lo Wing-lok, who represents the medical constituency, said boiled bleaching solution would do no
serious harm to the human body, but industrial grade hydrogen peroxide would affect our health.
Dr Lo explained that industrial grade peroxide demands a low purity and may be mixed with other substances
like organic and inorganic toxins, heavy metals like lead and biotoxins like arsenic. If they were absorbed into
the shark’s fin, they could cause various problems.
P. 1
© 2007 The University of Hong Kong – Faculty of Education. All rights reserved
Senior Form Chemistry – Hydrogen Peroxide
Article Two
Shark’s fin and industrial grade hydrogen peroxide
ABC Daily
The Quality Inspection Unit of Guangdong Province recently discovered that some factories processed shark’s
fin with industrial grade hydrogen peroxide. The process and raw materials by which the hydrogen peroxide
was produced may cause accumulation of impurities such as toxic heavy metals in the shark’s fin. These
factories are still in operation.
Properties and uses of hydrogen peroxide
Hydrogen peroxide, also known as hydrogen dioxide, is a compound made up of hydrogen and oxygen with
the chemical formula H2O2. Pure hydrogen peroxide is a colourless liquid which has a mainly oxidizing action
though it can also be reducing. Commercial hydrogen peroxide is usually available at concentrations ranging
from 3 % to 6 %, or 30% for medical or reagent uses.
Hydrogen peroxide solution is not stable. It decomposes to water and oxygen easily. The solution is bitter and
will produce bubbles in the mouth if taken in orally. It is a strong oxidizing agent. Clinically it is used as an
antiseptic to cure abscesses. It also bleaches organic matter such as hair, silk, wheat, ivory, bones and textiles,
and some kinds of food, in addition to being used as an oxidizing agent, antiseptic and chemical reagent etc.
Production of hydrogen peroxide
Due to the high purity required, hydrogen peroxide is produced by electrolysis. Usually, ethylanthraquinol is
oxidized by oxygen to give ethylanthraquinone and hydrogen peroxide. Palladium is then used to catalyse the
reduction of ethylanthraquinone to ethylanthraquinol by hydrogen. The cycle is repeated with consumption of
water, oxygen and hydrogen only.
The product obtained from the process described is highly pure because only very few impurities result,
therefore it is most suitable for the food processing industry. Though the raw materials needed are abundant in
nature, the production cost involved is high due to heavy investment in machinery and heavy consumption of
electricity during electrolysis and production of oxygen and hydrogen.
Hydrogen peroxide is not new to humans. Ancient people produced it with alkaline metals (such as potassium,
sodium) or alkaline earth metals (such as barium) or their oxides. Oxidation of these metals/oxides gives
peroxides which are then transformed to hydrogen peroxide when reacted with acidic solutions. Simple
equipment and low technical level are needed for production. The raw materials are also recyclable. Users may
produce crude or semi-products themselves, or buy the chemicals at low cost. This not only simplifies the
production process but also reduces the cost.
What is industrial grade hydrogen peroxide’?
The phrase ‘Industrial grade hydrogen peroxide’ as commonly used by the media is in fact imprecise. One
definition of industrial grade hydrogen peroxide is the product obtained from industrial manufacturing
processes. The chemicals produced from both processes described above belong to this class. Other definition
may either refer to the classification of hydrogen peroxide in terms of its composition, such as chemical
analysis grade, reagent grade (more pure) or industrial grade (lower grade products), or in terms of its uses into
clinical, food or industrial product, etc.
The so-called ‘industrial grade hydrogen peroxides’ actually refers to those types that are manufactured from
peroxides of the alkaline earth family as a result of cost-cutting. Most raw materials of alkaline earth metal
peroxides are minerals or primary industrial products and are mixed with impurities. For example, lead and
barium are two toxic chemicals dissolved in hydrogen peroxide instead of being extracted during the
transformation of metals and oxides to peroxides. ‘Industrial grade’ solution results if it is not purified.
P. 2
© 2007 The University of Hong Kong – Faculty of Education. All rights reserved
Senior Form Chemistry – Hydrogen Peroxide
Elimination of toxic hydrogen peroxide begins with standardized production procedures and strict control of
raw materials. Supervision and inspection of production, stringent legislation and enforcement are key issues
as well. It all relies on the Quality Inspection Unit of Guangdong Province.
According to the articles, discuss with your classmates of the same group and then
summarize and explain how bleached shark’s fin could affect our health.
Notes:
Article one
It is expected that the students cannot precisely point out it is the toxic impurities
(heavy metals) in the industrial grade hydrogen peroxide that brings harmful effect to
our health. Most likely the students will say that “hydrogen peroxide” can cause
cancer, stomach ulcers and other harmful effects to us, as wrongly suggested by the
subtitles.
Article two
Compared with the previous article, this article first provides the readers with the
knowledge of the chemical properties, physical properties and the everyday use of
hydrogen peroxide. It helps the readers to understand hydrogen peroxide so that the
image “Hydrogen peroxide = devil” shaped by the media can be clarified, since most
news in these years (like the first article) mainly highlight the misuse or potential
harmful effect of hydrogen peroxide (or the toxic impurities in it). News is a kind of
“media”
In the paragraphs “Production of hydrogen peroxide” and “What is industrial grade
hydrogen peroxide?”, the writer presents the production procedures for hydrogen
peroxide and lets the readers understand how the name “industrial grade hydrogen
peroxide” originated and why toxic impurities can be found in it. That is because some
merchants want to cut cost and use industrial grade hydrogen peroxide instead of food
grade hydrogen peroxide. Hydrogen peroxide which has not been purified should be
used only for industrial purpose not involving food production.
Though this writer does not say “hydrogen peroxide is harmless to health”, the article
clearly states that it is the toxic impurities found in industrial grade hydrogen peroxide
that may bring severe health effects, instead of the chemical, hydrogen peroxide, itself.
It is obvious that the second news article is more precise in the use of wording and
contents, and more comprehensive than the first article.
P. 3
© 2007 The University of Hong Kong – Faculty of Education. All rights reserved
Senior Form Chemistry – Hydrogen Peroxide
Part B - Seeking advice from reliable sources (Homework)
As shown in part A, the quality and reliability of newspaper reports
varies a lot. We may like to refer to some locally or internationally
recognized authorities for more guidance. Visit the website of the
Food and Environmental Hygiene Department of HKSAR (FEHD)
on http://www.fehd.gov.hk to search for information about the use of
H2O2 in food. The following questions help to check your
understanding after reading on the site.
Notes: The guideline about the risks of using hydrogen peroxide in food can be
obtained by searching the keyword “hydrogen peroxide” in the FEHD website.
(Please refer to Appendix 1.)
Q1.What is the mission of the Food and Environmental Hygiene Department of HKSAR?
To ensure that food is suitable for human consumption and to maintain a clean and
hygienic living environment for the people of Hong Kong.
Q2. What is the “IARC”? Try to search for it on internet and write down its role below.
The title of the first news article in part A said taking hydrogen peroxide can lead to
cancer. Is there adequate evidence for this claim according to IARC?
The International Agency for Research on Cancer (IARC) is an international
organization with the goal of identification of the causes of caner and development
of preventive measures against the cancers. According to IARC, there was still
inadequate evidence for carcinogenicity of H2O2in humans.__________________
Q3. In the section about “Safety of Hydrogen Peroxide”, the reports of an international body
JECFA are quoted. Do you know what JECFA stands for and what its purpose is?
JECFA - The Joint FAO/WHO Expert Committee on Food Additive
is an international expert scientific committee that is administered jointly by
the Food and Agriculture Organization of the United Nations (FAO) and the
World Health Organization (WHO). It has been meeting regularly to
evaluate the safety of food additives, food processing aids …etc
(Refer to the website for details)
According to JECFA, is hydrogen peroxide toxic to us?
According to JECFA, a small amount of hydrogen peroxide is not toxic because of rapid
decomposition of hydrogen peroxide by the enzyme catalase in the intestinal cells._______
Q4. According to the report of FEHD, is the level of hydrogen peroxide, remaining in
processed shark’s fin samples, harmful to our health?
Remark: Compare the answer of this question to your answer in Part A Q1.
As hydrogen peroxide is unstable, the level found in dry shark’s fin samples would not
affect health as the usual steps in preparation and cooking of shark’s fin would
effectively remove the remaining hydrogen peroxide_____
P. 4
© 2007 The University of Hong Kong – Faculty of Education. All rights reserved
Senior Form Chemistry – Hydrogen Peroxide
Part C – Shark’s fin: Enjoy it or Ban it? (Extension)
The bleaching of shark’s fin by hydrogen peroxide is widely reported in Hong Kong
since the demand for shark’s fin is very large in the Chinese communities. In fact
the consumption of shark’s fin is a very hot controversial issue. Why?
What is “Finning”?
Much of the shark's fins in the trade are cut from
living sharks. This process is called finning (只割魚
翅, 棄掉鯊魚). Because shark’s meat is worth very
little, the finless, usually still-living sharks are thrown
back into the sea to make room for more of the
valuable fins in the boat. When returned to the ocean,
the finless sharks, unable to swim, die from
suffocation or are eaten by sharks or other animals.
Finning is very strongly opposed by animal welfare groups, both on moral grounds and
also because it is a major cause for the rapid reduction of global shark populations, in
some cases by 99% over the last 50 years. Leading conservation ecologists predict that
widespread shark extinction will occur within 10 or 20 years.
Ban on Shark's Fin Dishes in The University of Hong Kong and Disneyland in
2005
Oct 2005 - The University of Hong Kong has recently considered a proposal from within
the University community to ban the serving of shark's fin dishes at University functions.
.
July 2005 - Hong Kong`s Disneyland abandoned the controversial shark’s fin soup on its
menus, replacing it with lobster bisque to be offered for wedding banquets.
References for finning:
The reality of shark finning
http://www.sharkfriends.com/sharkfinning.html
Stop consuming shark’s fin
http://www.chattergarden.com/node/860
Discussion
P. 5
You are a group of merchants that trade shark’s fins with
restaurants OR you are a group of Hong Kong Disneyland
senior managers that insist upon serving shark’s fin soup in
Disneyland wedding banquets. What propositions will you use
to support the continuing consumption of shark’s fin?
Search for the relevant news on internet and read the
propositions in support of and against the consumption of
shark’s fin for more information for this discussion.
© 2007 The University of Hong Kong – Faculty of Education. All rights reserved
Senior Form Chemistry – Hydrogen Peroxide
Activity 2
Study the kinetics of hydrogen peroxide
decomposition
Introduction
HARMFUL
CORROSIVE
The aim of this activity is to study the rate of decomposition of hydrogen peroxide at
different time intervals and different temperatures. Titration of hydrogen peroxide against
acidified potassium permanganate will allow us to determine the concentration of
hydrogen peroxide. The equation for the reaction is:
5H2O2 (aq) + 2MnO4-
(aq)+
6H+ (aq)  2 Mn2+ (aq) + 5O2 (g) + 8H2O (l)
Reaction rate, order of reaction and activation energy of decomposition of hydrogen
peroxide can then be determined by recording the data and plotting suitable graphs.
Objective

To determine the decomposition of 0.1% hydrogen peroxide solution at different
temperatures (room temperature, 60oC, 80oC and 100oC over a period of 30 minutes.
This can be achieved by determining the concentration of hydrogen peroxide solution
at a specific time (e.g. 0min, 5min, 10min, 15min, 20min and 30min).

To determine the order of reaction for the decomposition.

To determine the activation energy of the decomposition.
Chemicals
0.02M Potassium permanganate, 0.1% hydrogen peroxide
P. 6
© 2007 The University of Hong Kong – Faculty of Education. All rights reserved
Senior Form Chemistry – Hydrogen Peroxide
Apparatus
After you have designed the investigation, you can then list the amounts of
apparatus and the quantities of chemical reagents needed.
Hot water bath, iced water bath, 100ml conical flask (x 6), 25ml measuring cylinder
(x 6), 5ml pipette, 50ml burette, 250ml beaker, 1L/2L volumetric flask, thermometer,
test tube holder, Bunsen burner, tripod and stand, filter funnel, matches, stop
watch(x 6), stopper(x 6), dropper, glass rod
(Notes: This above list of apparatus is for the suggested procedures below only.
Students can have their own ways of achieving the aim of this experiment.)
Procedures
We need to find out the concentration of hydrogen peroxide at different time
intervals for each temperature. However, there are at least three areas that may
cause errors in this investigation.
A. When the hydrogen peroxide is heated up from room temperature to the desired
temperatures (e.g. 60oC), it will be decomposing during the process of heating.
B. Hydrogen peroxide solution will evaporate when it is in the water bath. The loss is
more significant at a higher temperature. This will affect the concentration of
hydrogen peroxide left.
C. Hydrogen peroxide will still undergo decomposition during the titration. We need to
stop/slow down the decomposition when the required time interval is reached.
The investigation should be designed so that the above errors can be minimized.
A. Instead of warming up the solution to 60oC by placing in water bath, the room
temperature hydrogen peroxide solution can be diluted with warm water. For example,
in preparing the solution at 60oC, we mix 5cm3 0.5% H2O2(aq) at ambient temperature
with 20cm3 65-70oC deionized water (the exact temperature depends on the ambient
temperature of the starting solution). (See step 3-4 below)
B. Stopper the flask loosely (because the decomposition produces oxygen gas) to minimize
evaporation). (See step 5 below)
C. Stop the reaction (quench it) by putting the conical flask in an ice bath as soon as the
time is reached. (See step 7 below)
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© 2007 The University of Hong Kong – Faculty of Education. All rights reserved
Senior Form Chemistry – Hydrogen Peroxide
Suggested key procedures / points for titration of hydrogen peroxide with permanganate at
60oC: (The same for other temperatures)
1. Pipette 5ml of 0.1% hydrogen peroxide to 6 conical flasks.
2. Label the conical flasks with “T=0min”, “T=5min”, “T=10min”, “T=15min”,
“T=20min” and “T=”30min”. (It is suggested that each student in a group should be
responsible for the timing and titration of 2 flasks)
3. Prepare some 70oC deionized water kept in a “Thermos” flask; put 20cm3 into
measuring cylinders.
4. Pour 20cm3 deionized warm water into each conical flask (This heats up the
hydrogen peroxide solution immediately). Start the timing.
5. Use stoppers to stopper the conical flasks loosely to prevent the evaporation of
hydrogen peroxide.
6. Keep the hydrogen peroxide solution in a 60oC water bath.
7. At time T = 0min, quench the reaction of the hydrogen peroxide solution in the flask
labelled “T=0min” with an iced water bath.
8. Titrate the hydrogen peroxide with 0.02M permanganate until end point is reached.
9. When the time reaches 5, 10, 15, 20 and 30 min respectively, quench the reaction
and start the titration as step 8.
Data Analysis
1.
For each temperature, record the results in the following table:
Time
(min)
Initial burette
Final burette
reading
reading
(cm3)
(cm3)
Volume of MnO4- used
(cm3)
Concentration of
H2O2
3
(M)/25cm
0
5
10
15
20
30
2.
From the experimental result for the decomposition of H2O2 at 100oC, what
do you conclude about the safety of consuming food which contains H2O2?
The decomposition rate of H2O2 at 100oC is very rapid. Any H2O2 can effectively be
removed from the food by boiling, even the safety of H2O2 is still uncertain.
P. 8
© 2007 The University of Hong Kong – Faculty of Education. All rights reserved
Senior Form Chemistry – Hydrogen Peroxide
3. With the help of the above data plot suitable graphs, find out the order of reaction
and activation energy for the decomposition of hydrogen peroxide.
Sample results for teachers’ reference
T=60C (first order plot, In[H2O2] vs t)
T=70C (first order plot, In[H2O2] vs t)
Time (min)
/ min
0
5
10
15
/ min
Time (min)
20
25
30
0
0.000
5
10
15
20
25
30
0.00
-3.340
-3.35
In[H2O2]
ln[H2O2]
-3.350
-3.360
-3.40
-3.45
-3.50
-3.370
-3.55
-3.380
-3.60
T=80C (first order plot, In[H2O2] vs t)
T=99C (first order plot, In[H2O2] vs t)
Time (min)
/ min
Time (min)
/ min
0
5
10
15
20
25
30
35
0
0.0
5
10
15
20
25
30
35
0.0
-3.2
-3.6
In[H2O2]
ln[H2O2]
-3.4
-3.6
-3.8
-4.0
-4.4
-4.8
-4.0
-5.2
-4.2
To determine Ea (Ink vs 1/T)
1/T / K-1
2.5x10
0
-3
2.6x10-3
2.7x10-3
2.8x10-3
Sample results:
-6
-7
Ink
-8
-9
-10
Ea = 103 kJmol-1
When T=99oC,
k = 9.73 X 10-4 s-1
Half life = 11.9 min
5 half-lives = 1 hr.
-11
-12
The decomposition is known to be a first-order reaction. Literature values for an uncatalyzed
decomposition of H2O2 ranged from 21 kJmol-1 to 96 kJmol-1.
Reference:
Lin, C.C., Smith, F.R., Ichikawa, N., Baba, T. & Itow, M. (1991) Decomposition of hydrogen peroxide in
aqueous solutions at elevated temperature, International Journal of Chemical Kinetics, 23, 971-987
P. 9
© 2007 The University of Hong Kong – Faculty of Education. All rights reserved
Senior Form Chemistry – Hydrogen Peroxide
Activity 3
Should we drink hydrogen peroxide?
Part A – News reports about the support and against of the
drinking of hydrogen peroxide to improve our health
During the outbreak of SARS, there was a religious group in Hong
Kong encouraging people to drink hydrogen peroxide to reduce the
risk of being infected by SARS virus. Should we follow their
example?
Part B – Alternative Medicine (Extension)
Part A – Should we drink hydrogen peroxide to improve our health?
Notes: Divide the students in groups to discuss the questions in part A.
The news clipping below is a summary of this incident.
Religious body preaches medical use of hydrogen peroxide Metro Daily 2004-01-14
Reports suggest that religious bodies near Tin Shui Wai and Yuen Long promote the use of hydrogen
peroxide as panacea for all kinds of illnesses. They claim that it can prevent SARS and cancer but the cure is
available only to members of the organization. Medical professionals warn that drinking hydrogen peroxide
damages the digestive tract and may even lead to haemorrhage. The school heads of Yuen Long district have
reported the incident to the Education and Manpower Bureau and the police. No student injury has been
reported so far but religious preaching activities by teachers have been blamed for the situation.
Can drinking hydrogen peroxide improve our health? There are many opinions
from different parties in news and media. Let us review the opinions critically
before believing any suggestion.
The article below presents some propositions that support the drinking of hydrogen
peroxide.
Hydrogen peroxide is not evil !- ABC Daily
Ancient wisdom tells us that stream water containing bubbles is most suitable for drinking. Bubbles are the
result of increased hydrogen peroxide content during rapid movement of water downstream. The curing
effect of spring water present in mountain streams is due to the hydrogen peroxide content. Honey and
freshly squeezed fruit juice are tastier than those reproduced from concentrates. Why is there the difference?
This is due to the traces of hydrogen peroxide present in unheated fresh fruits and vegetables. Ozone and
hydrogen peroxide are natural antiseptics and disinfectants. (1)
Disinfection by ozone or hydrogen peroxide has a long history in human water consumption in European
countries. Most world class swimming pools sterilize water with ozone. (2) This is a solution to the problem
of chlorination of water which causes irritation of the skin. Skin ages more rapidly and blood vessels harden
much faster when the chlorine absorbed by skin meets bad fatty acid in the blood.
In fact, during the flu epidemic in 1920, Dr. T. H. Oliver cured many patients by injecting hydrogen
peroxide into their blood through the veins. His practice was published in The Lancet, an English medical
P. 10
© 2007 The University of Hong Kong – Faculty of Education. All rights reserved
Senior Form Chemistry – Hydrogen Peroxide
journal. In the 80’s, Dr. Charles Farr, MD PhD published an article titled ‘Therapeutic Use of Intravenous
Hydrogen Peroxide’ and laid the foundation of intravenous injection of hydrogen peroxide. Doctors around
the world now uses ozone and hydrogen peroxide as cures for cancer, AIDS, bacterial infection, blood
circulation disorders, gangrene (壞疽), etc. (3)
Breast milk, especially first milk, contains hydrogen peroxide and can switch on an infant’s immune system.
When germs invade our body, phagocytes engulf and destroy them with the release of hydrogen peroxide.
Penicillin, an antibiotic, works also through hydrogen peroxide. Interferon which treats viruses also works
by stimulating the production of hydrogen peroxide in the human body to destroy the fat jacket surrounding
the viruses. It is well known that vitamin C is good for immunity. It works also by increasing the hydrogen
peroxide level in the body. (4)
Readers should be clear about the benefits of hydrogen peroxide!
The two articles below hold an opposite view to the above writer.
Curing with hydrogen peroxide only worsens illness
- Drug Education Resources Centre, The Society of Hospital Pharmacists of Hong Kong
Ming Pao 2004-02-02
Oxygen therapy is a kind of alternative therapy. It works by releasing oxygen inside the body using one or
more chemicals to help elimination of toxic cells or substances.
Oxygen therapy is said to be able to cure or help to cure illnesses like cancers, asthma, cardiovascular illness
and rheumatoid arthritis. Supporters believe that elevated oxygen level suppresses the growth of cancer cells
and enhances immunity. However there is still no scientific evidence in support of this theory. (1) Two
commonly used chemicals in oxygen therapy are ozone and hydrogen peroxide.
Hydrogen peroxide is a colourless and odourless liquid used in cleansing and disinfecting wounds. Misuse
of concentrations above 10% may result in poisoning. Some people claim that hydrogen peroxide can
strengthen the immune system, oxidize toxins in the body, kill germs and viruses, clean the alimentary canal
and cure cancers. However, no tests in animals demonstrated suppression of cancer cells, nor has evidence
been obtained that direct injection into cancer cells or circulatory system is medically effective. (2) Oral
intake of concentration as high as 35% leads to vomiting, burns in the oesophagus and stomach, and
possible death. Direct contact with skin or inhalation of highly concentrated hydrogen peroxide also
damages the body.
There have been reports that treatment of constipation with 10% hydrogen peroxide as enema (灌腸劑) led
to aching, rectal bleeding, ulcer of the colon, and necrosis (壞死) of the large intestine. Concentration of as
low as 0.75% also leads to air embolism (氣體栓塞) and necrosis of the large intestine due to blockage of
blood supply to mucosal tissues of the intestine by the large quantity of bubbles produced from the hydrogen
peroxide. Some victims suffered from blockage of veins or arteries due to oxygen bubbles released to the
circulatory system. Urgent treatment was needed to raise the blood pressure and oxygen saturation to save
their lives. (3)
In conclusion, hydrogen peroxide is not a universal medication and should not be misused. It is only
prescribed for external use but never internal consumption. A concentration of 6% can be used for
disinfecting wounds or washing the mouth while 30% may be used carefully for bleaching teeth. One should
always refer to medical professionals in case of doubt.
P. 11
© 2007 The University of Hong Kong – Faculty of Education. All rights reserved
Senior Form Chemistry – Hydrogen Peroxide
Hydrogen peroxide kills cells no matter good or bad
- Dr. Lo Wing Lok
Apple Daily 2004-01-19
Dr. Lo Wing Lok (Host of ‘Healthy Community’, RTHK 1, medical constituency representative of
Legislative Council)
Recently the public’s attention is drawn to the use of hydrogen peroxide as medical cure by religious groups.
Hydrogen peroxide is an oxidizing agent. It releases free oxygen radicals which are harmful to most body
tissues, therefore it is antiseptic. Due to this property, it is usually used externally as disinfectant for wounds
or medical equipment. Some people may wrongly relate this property to internal use for killing germs in the
body, and curing cancer and AIDS.
The public should note that: drinking hydrogen peroxide kills normal healthy cells in addition to germs or
cancer cells, including cells in the mouth, oesophagous and the mucosal layer of the intestine as the liquid
passes through the alimentary canal. Internal organs may bleed or be perforated. (4)
Greater danger lies ahead. Free oxygen radicals released by hydrogen peroxide can combine to form oxygen
particles in blood. Excess oxygen particles in the blood give oxygen bubbles which block blood vessels,
resulting in organ failure and possible death. (5)
Eat more anti-oxidizing agents such as fruits
Drinking oxidizing agents such as hydrogen peroxide contradicts modern anti-ageing philosophy which
states that ageing and chronic disease may due to damage by oxidizing agents such as free oxygen radicals.
The way to youth and health is to take in more anti-oxidizing agents, not the opposite. (6)
Food rich in anti-oxidizing agents include fresh vegetables and fruits, and those rich in vitamins C and E.
Internal use of hydrogen peroxide threatens health. Oral intake, intravenous injection and enema should be
stopped immediately.
As a smart science student, you should consider the views in all science related
articles carefully and not simply agree with the writer without your own analysis.
We will give you a tutorial on how to analyze a proposition systematically. You can
then apply the technique to analyze the propositions in the three articles above.
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© 2007 The University of Hong Kong – Faculty of Education. All rights reserved
Senior Form Chemistry – Hydrogen Peroxide
Tutorial on making judgments
Statement: Corruption is not just, so it is not acceptable.
We can break down this statement into “a proposition + a conclusion” as follows:
Corruption is not just. (Proposition / 論點)
Corruption is not acceptable. (Conclusion/結論)
Should we agree with or believe all propositions?
We should only agree with propositions that are founded and relevant. Founded (有基
礎的, 有根據的) propositions contain statements that are based on facts and evidence (i.e.
the propositions are true). Relevant (相關的) propositions are connected with what is
being discussed (the propositions have a meaningful relationship with the
conclusion).
Example 2: Since Hong Kong is situated at the North Pole, the weather of Hong Kong is
freezing all the seasons.
This proposition is not founded since Hong Kong is not situated at the North Pole.
(The proposition is false. However it could be relevant since the weather of Hong
Kong would be freezing if it were really situated at the North Pole. The relevance of
a proposition is no longer important if the proposition is false since we will not believe
something which is based on false evidence.)
Example 3: Glasses can correct short-sightedness. Peter, who is short-sighted, should
wear a pair of glasses to correct his short-sightedness.
This proposition is founded and relevant since glasses can correct shortsightedness.
(The proposition is true and has a clear meaningful relationship with the
conclusion.)
Example 4: This spider must be harmless and friendly to us because it is very colorful
and cute!
This proposition may not be relevant, though it can be founded. The color and
appearance of a spider give us very little information of its harmfulness and behavior.
(The proposition does not have a meaningful relationship with the conclusion.)
Example 5: There have been an increasing number of complaints against mobile phone
companies, so the services of mobile phone companies are becoming worse.
This proposition may not be relevant, though it can be founded. Since the increase in
complaints might only be due to the increase in the number of mobile phone users.
(The proposition does not have a meaningful relationship with the conclusion.)
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© 2007 The University of Hong Kong – Faculty of Education. All rights reserved
Senior Form Chemistry – Hydrogen Peroxide
Example 6: This school is just a 1 minute walk from our home, so it must be
academically the best school for our son.
This proposition may not be relevant, though it can be founded. The reputation,
academic performance, moral education…etc of a school are all important for providing a
good education to a student. Distance from home is an irrelevant issue.
(The proposition does not have a meaningful relationship with the conclusion.)
Golden Rule for proposition analysis
We would only believe in those propositions which are both
Founded and Relevant.
Classwork: Read the following passage and decide whether you would believe it.
As you know, chlorine has been used to disinfect swimming pool water for a long
time. Remember the SARS period, the government promoted the use of 1:99
chlorine bleach to clean up our homes. Chloride is so natural that you can find it in
common table salt….. These propositions suggest that we can drink chlorine water
to improve our immune system.
Steps: 1. Identify all the propositions.
2. Decide whether each proposition is founded and relevant.
Identify all the propositions:
1. Chlorine has been used to disinfect swimming water for a long time.
2. Government promoted the use of 1:99 chlorine bleach to clean up our homes.
3. Chloride is natural as it can be found in table salt ( sodium chloride )
Notes: All of the propositions have a common conclusion:
“We can drink chlorine water to enhance our immune system.”
Decide whether each proposition is founded and relevant:
1. Founded. Not relevant.
2. Founded. Not relevant.
3. Founded. Not relevant.
P. 14
© 2007 The University of Hong Kong – Faculty of Education. All rights reserved
Senior Form Chemistry – Hydrogen Peroxide
Now you should be well equipped with the basic skills for proposition analysis. The
writers of the three articles you read before are trying to persuade you to improve
your health by drinking hydrogen peroxide.
Important notes:
1. In the first article, all the propositions appearing in the passage are supporting
the viewpoint that “drinking hydrogen peroxide can improve our health”.
2. All the propositions in the first article are independent of each other, though all of
them share a common conclusion , “drinking hydrogen peroxide can improve
our health.” That means we should analyze the propositions one by one
independently, i.e. the failure of one proposition in the passage does not affect the
function or value of the other propositions in the passage.
3. In the second and third articles, all the propositions in the passage are supporting
the viewpoint that “drinking hydrogen peroxide cannot improve our health”.
4. All the propositions in the second and third articles are independent of each other,
though all of them share a common conclusion that “drinking hydrogen peroxide
cannot improve our health” . That means we should analyze the propositions one
by one, independently. i.e. The failure of one proposition in the passage does not
affect the function or value of the other propositions in the passage.
P. 15
© 2007 The University of Hong Kong – Faculty of Education. All rights reserved
Senior Form Chemistry – Hydrogen Peroxide
For the first article:
Identify all the propositions that support drinking hydrogen peroxide to improve
health and then determine whether they are founded and relevant.
Notes: You only need to write down the proposition, since all the propositions
should share a common conclusion, “drinking hydrogen peroxide can improve our
health”. Notes: Propositions are highlighted and numbered in the article
Proposition 1
Ozone/hydrogen peroxide is a natural antiseptic and disinfectant.
Is it founded and relevant?
No.
Notes: H2O2 is used as an antiseptic, disinfectant and deodorant. It has a weak
antibacterial activity.
Proposition 2
Disinfection by ozone / hydrogen peroxide has a long history in human water
consumption in European countries. Most world class swimming pools sterilize
water with ozone.
Is it founded and relevant?
No.
Notes: H2O2 is only used to treat contaminated water, but not drinking water. O3 is
not equivalent to H2O2
Proposition 3
Doctors around the world now uses ozone/hydrogen as cures to cancer, AIDS,
bacterial infection, blood circulation disorder, gangrene, etc. (3)
Is it founded and relevant?
No.
Notes: There have been cases in which the patients suffered from severe acute
haemolysis after receiving H2O2 by intravenous injection.
Proposition 4
The switching on of infant’s immune system, penicillin the antibiotic, interferon
which treats viruses, vitamin C, all work through the action of hydrogen peroxide.
Is it founded and relevant?
No.
Notes: For example, penicillin works by inhibiting bacterial cell wall production.
P. 16
© 2007 The University of Hong Kong – Faculty of Education. All rights reserved
Senior Form Chemistry – Hydrogen Peroxide
For the second and third articles:
Identify all the propositions against drinking hydrogen peroxide to improve health
and then determine whether they are founded and relevant.
Notes: You may only write down the proposition since all the propositions should
share a common conclusion, “drinking hydrogen peroxide cannot improve our
health”. Notes: Propositions are highlighted and numbered in the article
Proposition 1
There is still no scientific evidence in support of this theory.
Is it founded and relevant?
Yes.
Notes: Scientific evidence is essential to show that H2O2 is safe and can be used to
improve our health.
Proposition 2
No tests in animals demonstrated suppression of cancer cell, nor has it evidence that
direct injection into cancer cells or circulatory system is medically effective.
Is it founded and relevant?
Notes: There have been cases in which the patients suffered from severe acute
haemolysis after receiving H2O2 by intravenous injection.
Proposition 3
Many past cases proved that clinical use of hydrogen peroxide damages the body.
Is it founded and relevant?
Yes.
Notes: Safety issues are critical for any therapy.
Proposition 4
Drinking hydrogen peroxide kills normal healthy cells in addition to germs or
cancer cells.
Is it founded and relevant?
Yes.
Notes: But does it imply H2O2 can be used to treat cancer?
Proposition 5
Free oxygen radicals released by hydrogen peroxide indirectly result in organ
failure and possible death.
Is it founded and relevant?
Yes
Notes: But H2O2 decomposes to form O2 and H2O.
Perhaps it applies only when a high concentration of H2O2 is used.
P. 17
© 2007 The University of Hong Kong – Faculty of Education. All rights reserved
Senior Form Chemistry – Hydrogen Peroxide
Which article(s) can convince you to agree with its viewpoint? Why?
Notes:
Teachers should accept any point having reasonable justification.
Pros: cannot give evidence that taking H2O2 is useful for our health
Cons: cannot give evidence that taking a low concentration of H2O2 is definitely
harmful. Even so, what do you believe? Why?
In addition to the analysis above, students may also compare the sources of the
articles.
The second article is published from The Society of Hospital Pharmacists in Hong
Kong while the third article is by the medical constituency representation in
legislative council. The writer of the first article is not named. The writers for the
second and third article have to be responsible for what they write in newspapers
and both of them present the collective opinions of the medical field and the
legislators.
P. 18
© 2007 The University of Hong Kong – Faculty of Education. All rights reserved
Senior Form Chemistry – Hydrogen Peroxide
Part B – Alternative Medicine (Extension)
What is Alternative Medicine (另類醫療)?
Alternative medicine broadly describes methods and
practices used in place of, or in addition to, conventional
medical treatments. The precise scope of alternative medicine
is a matter of some debate and depends on the definition of
"conventional medicine." Common alternative medicine
around us includes practices that base on spiritual,
metaphysical (超自然的), or religious grounds; and some
non-European medical traditions. People who support one
class of alternative medicine may reject others.
Based on one of the news article above and the information on the internet, list
several practices of alternative medicine that involves the use of hydrogen peroxide.
Alternative medical practitioners suggested the doses of hydrogen peroxide intravenously
( 通過靜脈) in extremely low (less than one percent) concentrations for hydrogen peroxide
therapy - a controversial alternative medical treatment for cancer and AIDS. Another
therapeutic use of hydrogen peroxide is to cure colds and flus. Some alternative medicine
practitioners recommend inserting a few drops into each ear at the first sign of a cold.
According to their claims, for most people this will eliminate the cold virus at first attempt
within a few hours, with stated 80% success rate. (Reference: Wikipedia – Therapeutic use
of Hydrogen Peroxide)
Since alternative of medicine lacks sound scientific evidence and clinical tests to support
it. It is generally suppressed by major science communities. Below is a news article about
the use of hydrogen peroxide in alternative medicine in Hong Kong.
Admission of hydrogen peroxide is lethal
Ming Pao 2003-09-25
Alternative therapy Admission of hydrogen peroxide led to extensive debates in 1996. The medical
hearing held yesterday revealed that some registered doctors injected hydrogen peroxide into the
bloodstream of patients. Pharmacists commented that such practice may be lethal if mishandled.
According to Dr. Yuen Tai-ming, an alternative therapist, hydrogen peroxide belongs to a kind of
alternative therapy due to its disinfectant property. However Dr. Yuen only prescribes it for external use
such as treating periodontal disease. He commented that internal use or intravenous injection of hydrogen
peroxide was rare in Hong Kong. Dr. Chui Chun-ming, Project Director of the Drug Education Resources
Centre, The Society of Hospital Pharmacists of Hong Kong, also said that hydrogen peroxide was usually
used in cleansing wounds and bleaching teeth. Terrible side effects may result if it goes into the
bloodstream. Haemolytic anaemia may result if a solution of concentration of 35% or above is injected into
blood, leading to kidney failure and death.
Alternative medicine generally lacks sound scientific evidence
to support its effectiveness and safety. Why is there still a large
demand for it?
Discussion
P. 19
Try to name a few more practices of alternative medicine and
the reasons why they are popular in Hong Kong.
© 2007 The University of Hong Kong – Faculty of Education. All rights reserved
Senior Form Chemistry – Hydrogen Peroxide
Appendix 1: Reference for Activity 1 Part B
Teachers’ reference for Activity 1 Part B: The following two pages of information can be
obtained by searching the keyword “hydrogen peroxide” in the website of FEHD. Hints for
the above questions are highlighted in red for teachers’ reference.
Risk assessment of hydrogen peroxide by the Food and Environment Hygiene Department:
Introduction
Recently, there have been media reports regarding the use of industrial grade hydrogen peroxide as a
bleaching agent in the processing of shark’s fins and pistachio nuts.
Properties of Hydrogen Peroxide
1. Hydrogen peroxide (H2O2) is a strong oxidising agent that is commonly used in industry, in the
medical field and for bleaching hair!
2.
The anhydrous form of the chemical is a colourless, bitter-tasting liquid with an ozone-like odour.
3.
It is unstable and decomposes if open to the air, upon stirring (agitation), and exposure to light or
heating, producing water and oxygen.
Uses of Hydrogen Peroxide in Food Processing
1. Because of its strong oxidising property, hydrogen peroxide is used as a bleaching agent in some
foods such as wheat flour, edible oil, egg white etc. in countries such as USA, Canada, Australia
and New Zealand.
2.
It is also allowed to be used against micro-organisms in food, e.g. milk, and as a sterilizing agent
for food packaging materials, e.g. bottles or waxed cartons
3.
In processing food, the quantity of hydrogen peroxide should be limited to the amount sufficient
for the purpose.
4. In the Mainland, hydrogen peroxide is included in the list of food processing aids. In general,
processing aids used in food should be removed from the final products. (Q3)
Safety of Hydrogen Peroxide
1. The Joint FAO/WHO Expert Committee on Food Additives (JECFA) evaluated the safety
of hydrogen peroxide in 1965, 1973 and 1980 respectively. JECFA considered that ingestion
of small amounts of hydrogen peroxide would produce no toxic effects due to rapid
decomposition of the chemical by the enzyme catalyses in the intestinal cells. (Q4)
2.
Drinking of 3% hydrogen peroxide solutions (household strength) generally does not result in
severe toxicity but may result in vomiting, mild irritation to the mouth lining (epithelium) and
burns in the mouth, throat, oesophagus and stomach. Ingestion of higher concentration, e.g. >10%,
can result in more dangerous outcomes such as burns to mucus membranes and gut lining
(mucosa).
3. Regarding the possibility of cancer from hydrogen peroxide (carcinogenicity), the
International Agency for Research on Cancer (IARC) considered that there was inadequate
P. 20
© 2007 The University of Hong Kong – Faculty of Education. All rights reserved
Senior Form Chemistry – Hydrogen Peroxide
evidence for carcinogenicity in humans. (Q2)
4. Hydrogen peroxide is unstable and decomposes in contact with food and during cooking.
The situation in Hong Kong
1. In Hong Kong, hydrogen peroxide can be used in food as a bleaching agent provided that the
residue is removed in the finished products. Furthermore, only food grade hydrogen peroxide may
be used in processing food and the dosage used should be “limited to the amount sufficient for the
purpose.”
2.
Hong Kong has stepped up local surveillance on shark’s fins and pistachio nuts. 25 samples of
shark’s fin and 21 samples of pistachio collected from the local market, including those imported
from the Mainland, were sent to the Government Laboratory for testing of hydrogen peroxide.
Tests on preservatives and possible contaminants such as heavy metals were also performed.
3. 14 out of 25 shark’s fin samples were found to have residual hydrogen peroxide ranging from
0.0002% to 1.5%. This indicated that the processing of some shark’s fin had not followed good
manufacturing practice. As hydrogen peroxide is unstable, the levels found in the dry shark’s
fin samples would not have adverse health effects as the usual steps of preparation and
cooking of shark’s fin would effectively remove the remaining hydrogen peroxide, if any.
(Q5) Nevertheless, the traders were warned to adhere to good manufacturing and processing
procedures.
4. Hydrogen peroxide or preservatives were not detected in any of the pistachio nut samples. Test
results for heavy metals were found to be within permitted levels for both the shark’s fin and
pistachio nut samples.
Advice to the Trade
1. If hydrogen peroxide is used in processing food, only food grade hydrogen peroxide should be
used in processing food.
2. The amount of hydrogen peroxide to be used in food processing should be limited to the amount
sufficient for the purpose.
3. Appropriate measures should be taken to remove remaining (residual) hydrogen peroxide from the
finished products.
P. 21
© 2007 The University of Hong Kong – Faculty of Education. All rights reserved
Senior Form Chemistry – Hydrogen Peroxide
Appendix 2: Lesson Plan
Activity 1: Bleaching Shark’s fin with hydrogen peroxide
Time
Intended Learning Outcomes
Teaching Flow
Materials
 Aware that different newspaper clippings
 Teacher divides the class into small groups. Half of the
reporting on the same scientific issue does not
groups are given article 1, another half of the groups are
necessarily lead the readers to acquire the
given article 2.
correct scientific knowledge. Sometimes
imprecise wordings and titles can even mislead  Students are asked to read the articles in details. After
the readers.
reading students, students discuss the question “How
bleached shark’s fin could affect our health?” with group
members.
35 min
 Activity 1
worksheets.
Remarks
It is important that teachers do
not provide the students with
any comment of the articles
prior to the discussions to make
sure the students aware of the
misleading contents in the
newspapers themselves.
 One representative from each group is asked to present the
discussion results in front of class.
 Teacher helps the students to aware that it is the impurities
in the industrial grade hydrogen peroxide being harmful to
our health instead of the chemical, hydrogen peroxide
itself. It is expected students reading article 1 are less
likely to reach this conclusion as article 1 maybe
misleading.
P. 22
© 2007 The University of Hong Kong – Faculty of Education. All rights reserved.
Senior Form Chemistry – Hydrogen Peroxide
Activity 2: Study the kinetics of hydrogen peroxide decomposition
Time
Intended Learning Outcomes
 Understand how to design experiments to
investigate the kinetics of hydrogen peroxide
decomposition.
 Identify the errors of the experiment and
design suitable measures and procedures to
minimize errors.
 Able to justify the content of the newspaper
clippings by scientific investigation.
Teaching Flow
Materials
Remarks
 The focus of this part is not
 Teacher introduces the aim of the experiment is to

Activity
2
experiment techniques, but the
investigate the rate of decomposition of hydrogen peroxide
worksheets.
investigation results that lead to
so as to verify the reports of newspapers in activity 1.
the answers in question 2, which
 Teacher revises the equation of decomposition of hydrogen  Apparatus & is about the safety of consuming
food containing hydrogen
peroxide with students. Teacher encourages the students to
materials
peroxide.
design the experiment themselves and list out the apparatus
(depend on
and chemicals needed for the experiments.
the design
of the
experiment)
 Teacher discusses with students on the errors of the
experiment and the methods to minimize them.
70 min
 During the experiments, students are asked the complete
the data analysis table and discuss the questions 2 and 3
with groupmates.
P. 23
© 2007 The University of Hong Kong – Faculty of Education. All rights reserved.
Senior Form Chemistry – Hydrogen Peroxide
Activity 3: Should we drink hydrogen peroxide?
Time
Intended Learning Outcomes
 Understand the basic structure of an argument
as “proposition + conclusion”.
70 min
Teaching Flow
Materials
 Teacher introduces the activity by making the students
familiar with the controversy through reading the
newspaper clippings provided in the activity 3.
 Understand the proper way to analyze an
argument. The propositions of an argument have  Teacher helps the students to aware newspaper clippings
to be founded and relevant for us to believe it.
are composed of many arguments and it is important to
know a proper way to analyse the arguments
 Aware that newspaper clippings are formed by
systematically.
many arguments. It is necessary to identify them
and analyse them before believing them.
 Teacher conducts the tutorial of argument analysis to
students with the examples in the worksheets to illustrate
the necessity of the propositions being founded and
relevance for a valid argument.
 Activity 3
worksheets.
Remarks
The argument analysis tutorial
and the examples in activity 3
serve as a framework for
systematic analysis of
newspaper contents. Teachers
are strongly encouraged to
apply the framework to other
newspaper / magazine clippings
on other science related topics.
 Teacher practices argument analysis with students through
doing the classwork about drinking chlorine water to
improve health.
 Teacher makes sure students understand the structure of an
argument and the skill to analyse it. Students are asked to
identify the arguments in the newspaper clippings (about
drinking hydrogen peroxide) at the beginning and
determine whether the propositions are founded and
relevant.
P. 24
© 2007 The University of Hong Kong – Faculty of Education. All rights reserved.