Whoosh bottle

Whoosh bottle: Is using isopropanol as a fuel safer than using ethanol or methanol?

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Publication Date: 29 July 2019
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Answer by labsupport on question Whoosh bottle

The ‘Whoosh bottle’ activity demonstrates the combustion of an alcohol/air mixture. It is conducted using a 20L polycarbonate bottle with a narrow neck. When the fuel mixture is ignited it releases a large amount of energy accompanied by flames and a ‘whoosh’ sound.

This is a high-risk activity as the bottle has been known to explode1,2, fires have been caused3 and injuries have resulted under certain conditions.

Consideration is required as to whether the educational outcomes outweigh the risks and if you are permitted to conduct this in your school jurisdiction. The Queensland safety alert  Unpredictable science experiments4 contains safety principles to consider in determining whether alternative teaching resources, such as online videos, should be used.

It is important before and after the viewing of a high-risk activity, to carefully discuss the risks associated with such an activity and to discourage students from experimentation outside the school setting, to reduce the likelihood of injury.

There are reports of explosions occurring where

  • a glass bottle has been used5,6
  • the flammable liquid has sat in the bottle and possibly settled7 or
  • the flammable liquid has been placed into a warm bottle7
  • methanol has been used2

If this demonstration is to be conducted, it should only be performed by staff who are trained in the handling of flammable liquids. Science ASSIST recommends strict adherence to the following safety measures and procedure:

  • Never use glass bottles
  • Never enrich the bottle with oxygen
  • A written risk assessment be approved by a HoD or HOLA
  •  It is only performed as a demonstration (See references for a link to ‘Safety Guidelines for Chemical Demonstrations’).
  • Use only 70% isopropanol (also known as isopropyl alcohol, sec-propyl alcohol, propan-2-ol or 2-propanol8,9), due to its lower vapour pressure. It is less volatile than other alcohols and will therefore react less vigorously (and will be a slower, and arguably more enjoyable, reaction to watch).

Note: Science ASSIST does not recommend the use of other alcohols or fuels (including methylated spirits because the combustion products of the additives may be uncertain and/or hazardous) and strongly advises against the use of methanol due to its toxic properties.

The use of ‘rubbing alcohol’, which are 99% isopropanol (with appropriate dilution) or 70% isopropanol and 30% water9,10 are suitable. It is essential that you consult the relevant Safety Data Sheet to determine its suitability. Some formulations may be ethanol based and/or include additional hazardous components.11

  • Trial the activity first without an audience if the demonstrator is unfamiliar with this activity.
  •  Always ensure that the polycarbonate bottle is in good condition, no glazing, frosting or cracking. Only use cylindrical bottles (not rectangular bottles)7.
  • Always use a cool dry bottle if more than one demonstration is to occur, have several bottles ready. If a flammable liquid is placed into a hot bottle, a flash-back can occur, causing a fire.12,7
  • Always use a safety screen, perform in a location with good ventilation, a high ceiling of at least 2.5-3m above the top of the bottle and not under smoke/heat detectors or any combustible materials
  • Ensure the demonstrator is wearing PPE (laboratory coat, safety glasses and closed in shoes)
  • Ensure spectators are more than 4 metres away and are wearing safety glasses
  • Ensure that a fire extinguisher and fire blanket are close by and that you know how to use them
  • Measure the amount of alcohol used and pour out the excess alcohol and remove from the area. Always keep the stock bottle of alcohol in a different area well away from this demonstration
  • Use a taper attached to a metre ruler and light away from the bottles to enable a safe distance between the demonstrator and the bottle
  • Mark the bottle as “not suitable for storing water for human consumption” (So that it is not inadvertently recycled)

Procedure:

(We suggest conducting the demonstration in a darkened area to enhance the visual effect.)

  1. Make sure the bottle is completely dry.
  2. Add 25mL of isopropanol to the bottle and roll the bottle to coat the inside, pour out any excess and remove from the area. Wipe up any spill from the outside of the bottle.
  3. Place the bottle behind a safety shield.
  4. Light a taper and hold it over the neck of the bottle via a metre ruler to provide a safe distance.
  5. The isopropanol combusts with a whoosh sound and a yellow flame.
  6. Allow the bottle to cool, rinse out with water and completely dry before reuse.

References

[1] CLEAPSS. 2010. Bulletin 137-Spring 2010 https://science.cleapss.org.uk/login.aspx/?returnto=/resource/bulletin-137-spring-2010.pdf (Login required)

2 SSERC. 2018. ‘Whoosh bottle alert’, SSERC Bulletin 262, Spring 2018, p. 16, SSERC website, https://www.sserc.org.uk/publications/bulletins/262-spring-2018/

3 ‘Experts: Little oversight of Minn. classroom science labs’, Minnesota Public Radio website, https://www.mprnews.org/story/2011/12/11/class-lab-safety (11 December 2011)

4 ‘Unpredictable science experiments’, Safety Alert, Education Queensland website, https://education.qld.gov.au/initiativesstrategies/Documents/unpredictable-science-experiments.pdf (August 2018)

5 Howell, J. Emory. 2001. ‘Initiating Proactive Safety Leadership’, JChemEd, Vol. 78:1, January 2001, p.9, ACE Publications website, https://pubs.acs.org/doi/pdf/10.1021/ed078p9

6 Nuffield Foundation, n.d.‘The ‘whoosh’ bottle demonstration red risk assessment’, The Royal Society for Chemistry website, https://www.rsc.org/globalassets/18-events/risk-management/example---the-whoosh-bottle-demonstration-red-risk-assessment.pdf

7 ‘"Whoosh Bottle" and safety discussion’, University of Waterloo website, https://uwaterloo.ca/chem13-news-magazine/march-2015/feature/whoosh-bottle-and-safety-discussion (March 2015)

8 ACI Labscan. 2017.Propan-2-ol, Safety Data Sheet, Chem Supply website, https://www.chemsupply.com.au/documents/LC1162M.pdf (12 December 2017)

9 Recochem. 2017. Isopropyl alcohol, Safety Data Sheet, Diggers website, http://diggersaustralia.com.au/wp-content/uploads/sds/Isopropyl%20Alcohol%20v6.pdf (24 May 2017)

10 ‘Isocol Rubbing Alcohol 345ml’ Safety Data Sheet, AboutFaceOnline website, http://www.aboutfaceonline.com.au/wordpress/wp-content/uploads/2016/07/Isocol_MSDS_2015.pdf  (17 July 2015)

11 Rubbing alcohol’, Wikipedia, https://en.wikipedia.org/wiki/Rubbing_alcohol  (Accessed July 2019)

12 ‘Whoosh bottle’, Flinn Scientific website, https://www.flinnsci.ca/whoosh-bottle/dc10573/ (2016)

 

Flinn Scientific, 2016. Methyl Alcohol Safety, Safety Fax, Flinn Scientific website, https://www.flinnsci.com/api/library/Download/762ec945eb5744518e71a014f92818cb (6 June 2016)

‘Safety Guidelines for Chemical Demonstrations’, Division of Chemical Education, Inc. of the American Chemical Society website, http://www.divched.org/content/safety-guidelines-chemical-demonstrations  (Accessed July 2019)

‘The ‘whoosh’ bottle demonstration’, RSC Learn chemistry website, http://www.rsc.org/learn-chemistry/resource/res00000708/the-whoosh-bottle-demonstration?cmpid=CMP00005923 (October 2015)

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