Is there a place for 30% peroxide in High School Chemistry?

In a recent blog post, the activity Elephant’s Toothpaste was demonstrated. The activity was in keeping with our STAO safety policy regarding chemical use. In that policy, we suggest the use of small quantities of chemicals, at as low a concentration as possible to allow the reaction to proceed. Teachers are also asked to explore safer alternatives to replace reactions that introduce an unacceptable element of risk. In this video, it was suggested that the reaction proceed with 3 or 6% hydrogen peroxide, yeast as a source of catalase, soap and food colouring. As expected, the reaction proceeded well with a coloured soapy foam spilling out of the container. This was a good example of putting our policy (low concentrations, safer alternatives). As peroxide, even in low concentrations (6%), can cause serious damage to eyes, goggles should have been worn by the student in the video.

Hazards of 30% Hydrogen Peroxide

STAO recommends that 30 % hydrogen peroxide be only used by the teacher.  Its hazards include:

  • It can act as either an oxidyzing agent or reducing agent
  • It is caustic
  • It can decompose rapidly in the presence of catalysts
  • It can rapidly decompose when exposed to metal impurities (especially multivalent)
  • It can spontaneously ignite organic materials such as cotton, leather, paper towels

While these properties may seem alarming, they are common among the other oxidizers that are in our chemical inventory and used for lab activities and demonstrations. The “Teacher Use” designation should signify to teachers that the substance has a hazard level above the chemicals used for student activities. Precautions for the use of 30 % hydrogen peroxide include goggles, acid resist gloves, synthetic apron and keeping students at a safe distance from the demonstration. A self-standing chemical shield (aka explosion shield) is also reduces the risk injury without obscuring the view.

Recommended Video Resource 

Evonik Industries has produced a 30-minute training video (see link below) covering the industrial use of 50 -70% hydrogen peroxide. The video provides several neat demonstrations showing rapid decomposition, reaction to impurities and spontaneous combustion. It offers several good safety tips appropriate for high school. These include:

  • Never pour a decanted sample back into a stock bottle
  • Store peroxide at less than 30′ C
  • Store the stock bottle within a plastic tray
  • Use non-organic PPE’s (not leather)
  • Do not wipe spills with paper towels or natural cloths.
  • Even very dilute solutions can cause serious eye damage

 

Dave Gervais

Chair STAO Safety Committee

Resources 

1) H2O2 Safety Training Video – Evonik is a leading global manufacturer of hydrogen peroxide

Link to Video

2) Link to Picture of  Hydrogen Peroxide burns (35%)

 

 

 

 

 

Classification of Lasers Question to the STAO Safety Committee

laser 2Question:

The STAO Safe on Science document (2011) indicates that only class 1 and class 2 lasers are recommended for use in high school science classes. Many of the documents that I have examined indicate that Class 3A (old classification), now called Class 3R (new classification) are also safe, unless viewed through an optical device. I respectfully request that the safety committee re-examine this issue, and include Class 3R in the  recommendation.

Click for the committee’s response.  

 

Teacher Demo/Student Activity: Iron in Cereal

iron-in-cerealFood labels often contain the word ‘fortified’.  This means that one or more ingredients have been added that are not normally found in that food item.  The purpose is to increase the amount of that mineral or nutrient to serve a dietary purpose.  Table salt is fortified with iodine (to help prevent hypothyroidism, which can lead to goiter which is the abnormal enlargement of the thyroid gland), and many breakfast cereals are fortified with fibre (to improve digestion) and iron.

Iron ions (Fe3+) are essential for the formation of red blood cells.  They are central to the hemoglobin molecule, which is responsible for the transfer of oxygen gas and carbon dioxide throughout the body.  Iron ions are also found in muscle tissue and many enzymes.  Iron is often added to cereal in its elemental form (Fe) because it is more stable and has a minimal effect on flavour.

The recommended daily intake of iron depends on age and gender.  These values are listed in the Additional Resources section, and information about iron content in food can be found in the nutritional facts label on the packaging.

The purpose of this demonstration/activity is to illustrate the importance of proper labeling and identification of substances and the presence and form of iron in breakfast cereals.

Click here to download complete activity……

Borax Slime Activity Concerns Update

Borax Advisory Update Health Canada

Health Canada issued an advisory this past summer, suggesting that exposure to boron substances be reduced as much as possible from all sources. They identified boron substances as a developmental and reproductive health risk. They also stated that parents should not make slime and putties with borax and boric acid. By extension, teachers began to question the safety of making slime in their science classes. In response to questions posed by the STAO Safety Committee, Health Canada has clarified their advisory issued this past summer.

Regarding the use of Borax/Boric Acid, Health Canada wrote:

The proper use of gloves and goggles will reduce exposures to chemical substances. The main concern with the use of boron containing substances for making slimes or putties, is with accidental or intentional ingestion. This ingestion hazard is mainly targeted at young children who are prone to hand-to-mouth activities.

High school students, who have received proper training in hazardous material handling, and who are properly supervised to prevent ingestion, would be at low risk of exposure to boron, or other hazardous materials used as part of a science curriculum. The safe disposal of any boron containing substances should be closely monitored to prevent accidental or intentional ingestion.

Students younger than high school age, and those who have not been properly advised in the safe handling of laboratory chemicals should not be using borax, or any other hazardous chemicals at home or in a school setting.

Suggestions for activities involving borax or boric acid:

Although the chemicals containing boron do not readily cross the skin barrier, steps could be taken to prevent skin contact. Students could be issued gloves or alternatively, the ingredients for slime could be placed in a sealed plastic bag and then mixed. Students should be instructed to wash their hands at the end of the lab activity. Teachers should then collect the slime prior to dismissal to ensure that accidental or intentional ingestion does not occur. The slime can then be thrown out with the regular garbage.

Some suggested safer alternatives, for making slime or putties involving glue, have a high volatile organic compound (VOC) content and release this into the air. However, other glue and borax free recipes are available on-line and teachers are encouraged to explore the use of these safer alternatives.

We hope that the information in this response will help you in making an informed decision as to the use of boron containing substances in teaching science. Our safety committee can be contacted with your safety questions at info@stao.org, attention STAO Safety Committee.
Dave Gervais
Chair STAO Safety Committee