Teacher S Version (With Video Exemplars)

Senior Form Chemistry – Hydrogen Peroxide

Hydrogen Peroxide (H2O2) Teacher’s Version (with video exemplars)

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.

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If the links do not work, try again by pressing the “Ctrl” key and clicking the icon at the same time. Table of Contents Introduction (i) Activity 1: Bleaching shark’s fin with hydrogen peroxide Part A: News reports about the danger of bleaching shark’s fin with hydrogen peroxide P.1 Part B: Seeking advice from reliable sources Part C: Extension – Shark’s fin: Enjoy it or Ban it? Activity 2: Studying the kinetics of decomposition of hydrogen P.6 peroxide Activity 3: Should we drink hydrogen peroxide? Part A: News reports for and against drinking hydrogen peroxide to improve health P.10 Part B: Extension: Alternative Medicine Appendix 1: Reference for Activity 1 Part B P.20 Appendix 2: Lesson Plan P.22

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 5 lessons (each lesson 35 – 40 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)

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 OneTwo Over-consumption can cause cancer and deform foetuses SharkSing Tao Daily’s fin 2003-12-05 and industrial grade hydrogen peroxide ABC Daily Guangdong government officials have discovered a factory using industrial grade hydrogen peroxide to treat sharkThe Qualitys fins. It Inspection might upset Unit people of Guangdong to know that Province this delicacy recently is discoveredpotentially carcinogenic.that some factories processed shark’s fin with industrial grade hydrogen peroxide. The process and raw materials by which the hydrogen peroxide Awas pharmacist produced and may a doctorcause accumulationpointed out that of industrial impurities grade such hydrogen as toxic peroxideheavy metals is very in concentrat the sharked’s . fin.Also, These it is manufacturedfactories are still carelessly in operation. 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. Properties and uses of hydrogen peroxide The colourless liquid may lead to stomach ulcers 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 Likethough water, it can hydrogen also be reducing.peroxide isCommercial a colourless hydrogen liquid. It peroxide is used as is ausually bleach, available oxidizer ator concentrations germicide in industry. ranging Industrialfrom 3 % tograde 6 %, hydrogenor 30% for peroxide medical hasor re aa gent high uses. 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.Hydrogen peroxide solution is not stable. It decomposes to water and oxygen easily. The solution is bitter and Awill doctor produce stated bubbles that if inour the body mouth absorbs if taken too inmuch orally. oxygen, It is ait strong can damage oxidizing cell agent.membrane Clinicallys and speedit is used up aging. as an Hence,antiseptic it isto generallycure abscesses. not recommended It also bleaches. But organic it is used matter by some such asnaturopathic hair, silk, wheat,medicine ivory, specialists bones and for textiles,treating diseases.and some kinds of food, in addition to being used as an oxidizing agent, antiseptic and chemical reagent etc.

ProductionStill toxic after of hydrogen boiling peroxide Professor Lee Kwing-chin of The School of Pharmacy, CUHK indicated that diluted hydrogen peroxide Duebleach to isthe not high very purity harmful required, to human hydrogens. However peroxide the concentrationis produced by of electroly industrialsis .grade Usually, hydrogen ethylanthraquinol peroxide is sois oxidizedhigh that byit mayoxygen damage to give the ethylanthraquinone digestive system. Also,and hydrogen prolonged peroxide. absorption Palladium or massive is then absorption used to catalysecould cause the reductionulcer. He saidof ethylanthraquinone that medical literature to ethylanthraquinol has indicated an associationby hydrogen. between The cycle hydrogen is repeated peroxide with and consumption cancer. of Legislatorwater, oxygen Lo Wing-lok,and hydrogen who only. 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. DrThe Lo product explain obtaineded that industrial from the grade process peroxide described demands is highly a low purepurity because and may only be mixveryed fewwith impurities other substances result, liketherefore organic it is and most inorganic suitable toxins, for the heavy food processingmetals like industry. lead and Thoughbiotoxins the like raw arsenic. materials If they needed were are absorbed abundant into in thenature, shark the’s productionfin, they could cost cause involved various is high problems. 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,

P. 1 © 2007 The University of Hong Kong – Faculty of Education. All rights reserved Senior Form Chemistry – Hydrogen Peroxide 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.

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:

A rticle 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.

A rticle 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.

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______

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

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? Discussion 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.

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:

- + 2+ 5H2O2 (aq) + 2MnO4 (aq)+ 6H (aq) ® 2 Mn (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

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,

o 3 in preparing the solution at 60 C, we mix 5cm 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)

Suggested key procedures / points for titration of hydrogen peroxide with permanganate at

60 oC: (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: Initial burette Final burette Concentration of - Time Volume of MnO4 used reading reading H2O2 (min) (cm3) 3 3 3 (cm ) (cm ) (M)/25cm 0 5 10 15 20 30 o 2. From the experimental result for the decomposition of H2O2 at 100 C, 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. 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

o o T=60 C (first order plot, In[H2O2] vs t) T=70 C (first order plot, In[H2O2] vs t) Time /(min) min Time /(min) min

0 5 10 15 20 25 30 0 5 10 15 20 25 30 0.000 0.00 -3.340 -3.35

-3.350 -3.40 ] ] 2 2 O O 2

2 -3.45 H [ H -3.360 [ n l n I -3.50

-3.370 -3.55

-3.380 -3.60 o o 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 5 10 15 20 25 30 35 0.0 0.0 -3.2

-3.4 -3.6 ] ] 2 2 -3.6 -4.0 O O 2 2 H H [ [ -4.4 n n I l -3.8 -4.8 -4.0 -5.2

-4.2 To determine Ea (Ink vs 1/T) 1/T / K-1 2.5x10-3 2.6x10-3 2.7x10-3 2.8x10-3 0 Sample results: -6

-7 Ea = 103 kJmol-1 o -8 When T=99 C,

k -4 -1 n -9 I k = 9.73 X 10 s Half life = 11.9 min -10 5 half-lives = 1 hr. -11

-12 The decomposition is known to be a first-order reaction. Literature values for an uncatalyzed -1 -1 decomposition of H2O2 ranged from 21 kJmol to 96 kJmol . 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

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

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.

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.

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.)

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.

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.

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.

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.

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.

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?

Try to name a few more practices of alternative medicine and Discussion the reasons why they are popular in Hong Kong.

P. 21 © 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 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.

Appendix 2: Lesson Plan

Activity 1: Bleaching Shark’s fin with hydrogen peroxide Time Intended Learning Outcomes Teaching Flow Materials Remarks  Aware that different newspaper clippings  Teacher divides the class into small groups. Half of the  Activity 1 It is important that teachers do reporting on the same scientific issue does not groups are given article 1, another half of the groups are worksheets. not provide the students with necessarily lead the readers to acquire the given article 2. any comment of the articles correct scientific knowledge. Sometimes prior to the discussions to make imprecise wordings and titles can even mislead  Students are asked to read the articles in details. After sure the students aware of the the readers. reading students, students discuss the question “How misleading contents in the bleached shark’s fin could affect our health?” with group newspapers themselves. members.

 One representative from each group is asked to present the 35 min 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.

Activity 2: Study the kinetics of hydrogen peroxide decomposition Time Intended Learning Outcomes Teaching Flow Materials Remarks  Understand how to design experiments to  Teacher introduces the aim of the experiment is to  The focus of this part is not investigate the kinetics of hydrogen peroxide investigate the rate of decomposition of hydrogen peroxide  Activity 2 experiment techniques, but the decomposition. so as to verify the reports of newspapers in activity 1. worksheets. investigation results that lead to the answers in question 2, which  Identify the errors of the experiment and  Teacher revises the equation of decomposition of hydrogen  Apparatus & is about the safety of consuming design suitable measures and procedures to peroxide with students. Teacher encourages the students to materials food containing hydrogen minimize errors. design the experiment themselves and list out the apparatus (depend on peroxide. and chemicals needed for the experiments. the design  Able to justify the content of the newspaper of the clippings by scientific investigation.  Teacher discusses with students on the errors of the experiment) 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.

Activity 3: Should we drink hydrogen peroxide? Time Intended Learning Outcomes Teaching Flow Materials Remarks  Understand the basic structure of an argument  Teacher introduces the activity by making the students  Activity 3 The argument analysis tutorial as “proposition + conclusion”. familiar with the controversy through reading the worksheets. and the examples in activity 3 newspaper clippings provided in the activity 3. serve as a framework for  Understand the proper way to analyze an systematic analysis of argument. The propositions of an argument have  Teacher helps the students to aware newspaper clippings newspaper contents. Teachers to be founded and relevant for us to believe it. are composed of many arguments and it is important to are strongly encouraged to know a proper way to analyse the arguments apply the framework to other  Aware that newspaper clippings are formed by systematically. newspaper / magazine clippings many arguments. It is necessary to identify them on other science related topics. 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. 70 min

 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.