Ryleigh Barta, a grade 11 student from Jeannette Gobolos’ chemistry class at Lake City Secondary School in Williams Lake, British Columbia captured the ‘Whoosh Bottle’ demonstration in this photo. This photo gives Chem 13 News the opportunity to share a teacher’s frightening experience with this demonstration. It informs and reminds readers about necessary safety considerations.
‘Whoosh Bottle’ safety discussion
As editor of Chem 13 News I have seen the ‘Whoosh Bottle’ demonstration at almost every chemical education conference and outreach event — it remains an audience and classroom favourite. You can see by the cover photo how impressive this demonstration is. There are several fun variations.1,2,3
For a long time I had never met anyone who has had a problem with the ‘Whoosh Bottle’, but I had heard of accidents. Chem 13 News and Journal of Chemical Education have published several safety pieces about this demonstration4,5,6 based on these accident accounts, many of which started to come to light in the late 1990s. It is recommended that anyone attempting this demonstration — even if you have already done so — read and follow these safety recommendations. I finally found a chemistry teacher who had a negative experience in the 1990s as a student teacher. Thank you, Erica for sharing your ‘Whoosh Bottle’ experience.
We also asked John Fortman and William Deese — who were involved with writing up the safety articles4,5,6 almost 20 years ago — to comment on Erica’s experience and the general safety of this demonstration.
From Erica Larade, Fredericton NB
I don’t do the ‘Whoosh Bottle’ demonstration. It is simple to explain when someone asks why. It is based on my own class-room experience as a student teacher almost 20 years ago.
I would like to share this experience with other chemistry teachers.
My mentor teacher had done the ‘Whoosh Bottle’ demonstration for many years without incident. He used it in biology class to illustrate the large amounts of energy produced in aerobic cellular respiration versus anaerobic cellular respiration. He added about 10 mL of an alcohol to a large water jug like those found on office water coolers. For those unfamiliar with the experiment, you add the alcohol* to the jug and swirl it around so that it fully vaporizes — pouring out the excess liquid. You then light a match on a long stick and bring it to the mouth of the jug, and the alcohol vapors ignite in a spectacular rocket-engine-like fire and signature "whoosh" sound. The students are all impressed and cries for "More!" and "Again!" invariably ring out. So, the same amount of alcohol is added to the same jug, and ignited, but this time only a small, weak flame is emitted. The lesson: oxygen (aerobic respiration) allows for more energy production (more spectacular flame).
In this particular case, the demo for the first class went off without a hitch, and the water jug was put under the fume hood until I would repeat the demo for the next class, which happened to meet the next day. This schedule was new for the school. On the following day, I set everything up as planned during class.
I followed all the safety precautions that were given at that time and did the demonstration exactly like I had the day before. I added the correct amount of alcohol and used the same bottle, ignited the match and BOOM! The jug exploded with a sonic blast into hundreds of flaming bits of plastic scattered across the classroom! Teachers from down the hall came running, thinking a bomb had exploded. None of the students were hurt (thank God!) and we all stomped out the burning bits. If you thought the students were impressed with the "whoosh" the first time, you can imagine how excited they were to have me do it a second time! My nerves were shot, and my mentor teacher took the reins at that point, so they didn't get their second, less impressive, flame.
So, what went wrong? First, I believe the change in scheduling may have been a factor. In the past, this demonstration had been repeated for multiple classes in one day, rather than storing the bottle overnight between classes. When the demo was repeated in the same day, the second dose of alcohol was rinsed out with water to prepare for the next class. A hairdryer was used to blow air back into the jug before the next class. In the case that went wrong, not only was the second dose of alcohol not burned off completely, but the remainder was allowed to fully vaporize in the jug overnight (i.e., no rinsing). When I added the "first" 10 mL of alcohol the next day, unbeknownst to me I was actually adding MORE than was already in the jug — too much fuel equals BIG explosion!
Second, I believe the age and shape of the jug need to be taken into account. The jug had been used for several years and probably had cracks and weak points which, under normal circumstances, wouldn't be a factor, but when the extra fuel was taken into account those weak areas gave way under pressure.
I was lucky that the jug exploded away from me or things could have been a lot worse. I don't know if the fact that the jug was rectangular instead of round made a difference in the amount of force it could withstand or not.
This close call was chilling to me as a student teacher and I will never forget it.
References
* After 20 years, I don’t remember what alcohol was used.
At that time both methanol and ethanol were commonly used.
Editor’s comments
Flinn Scientific Chemfax uses isopropyl alcohol and outlines this demo and details safety at flinnsci.com/media/484580/95010-r.pdf.
It is advised not to use methanol for this and many other demonstrations because of many accidents. Methanol accidents often result when the methanol stock bottle is brought into the classroom. The cover of the methanol bottle is accidentally left off or opened in the presence of an open flame.
Safety recommendations
John J. Fortman stated in his 1999 article1 that “the most important precautions to be taken in these demonstrations are:
- undiluted alcohols should never be used in glass bottles;
- pure oxygen or any gas mixture with a concentration of oxygen higher than air should not be used;
- when using methanol or ethanol, neither the alcohol nor the bottle should be heated above room temperature;
- plastic jugs should be replaced when they begin to show grazing, frosting, or cracking;
- safety shields must always be in place, because even the mildest of these explosions have some chance of the bottle shattering; and, of course
- safety goggles must be worn.”
Comments from John Fortman
Retired, Wright State University, Dayton OH
After reading about Erica’s experience, I have some serious concerns. Alcohol should never be poured immediately into a bottle which is still hot. Many recent accidents have involved fires due to adding alcohol to a hot container, whether a whoosh bottle or the colored flames from salts in dishes of alcohol. NEVER USE HOT OR WARM ALCOHOL OR BOTTLES.
I am wondering about the second day use. More alcohol should not necessarily give more reaction as oxygen is the limiting reagent. Adding 10 mL more should not necessarily increase the reaction. Only the vaporized alcohol reacts. When I do this demonstration,
I don't measure the amount but pour out the excess after shaking it around. However, liquid alcohol can vaporize with heat during the reaction adding fuel in addition to the amount in the saturated vapor. Once when we used a cold jug we observed liquid in the bottle burning while the plastic jug melted down.* In Erica’s case, the bottle might have been warm so the extra alcohol might have had a higher vapor concentration leading to a faster and more violent reaction. ALWAYS POUR OUT EXCESS LIQUID. If I was not retired and had ready access to a lab I would be interested in doing some tests to determine how much alcohol in excess of 10 mL actually vaporized.
The rectangular bottle could have been a contributing factor as the stress would not be as uniform as in a cylinder. We never used anything but cylindrical ones with or without handles. I've also wondered if the size of the opening might have an effect such that too small a mouth might restrict the exit and increase the force on the walls causing shattering.
With regards to Ken Lyle's demos using 2-L pop bottles3, the soft plastic bottles often get hot enough to soften. I recommend the same bottle never be reused. This also eliminates the danger of a student pouring more alcohol into a bottle which is still hot. This may have been responsible for several accidents where students have been seriously burned by hot splashing alcohol. There was an accident like this in Cincinnati when a college student was doing this for a grade school class.
Personally, I am angered by how many demonstrators do not use a safety shield, especially once the safety warnings have been brought to their attention. Many feel it is overkill because they claim to have done it hundreds of times without an accident. Once you have the first one, it can be too late. It also sets a bad example.
The cover photo is great.
*If I thought I could reproduce it, it would make for a great humorous demonstration video.
Comments from William Deese
Louisiana Tech University, Ruston LA
I have performed whoosh bottle and ring of fire demonstrations1,5 hundreds of times without incident. For safety I always follow the guidelines listed above. It should also be noted that I use department store variety rubbing alcohol. It is 70% isopropyl alcohol and 30% water and burns less hot than pure alcohols.
As well, when performing the demonstration several times, I always fill the bottle full of water and then empty it. This will fill the bottle with fresh air while rinsing out the residual chemicals.
References
Some ‘Whoosh Bottle’ variations
- W.C. Deese, Chem 13 News, The ring of fire demonstration, November 1996, pages 8-9.
- Dean J. Campbell, Journal of Chemical Education, An Alcohol Rocket Car — A Variation on the ‘Whoosh Bottle’ Theme, July 2001, page 910.
- Natalie Miller and Kenneth Lyle, Chem 13 News, Miniature ‘Whoosh Bottle’ Demonstration, November 2012, pages 12-13.
‘Whoosh Bottle’ safety articles
- John J. Fortman, Chem 13 News, Safety precautions for the ‘Ring of Fire’ and ‘‘Whoosh Bottle’’ demonstrations, September 1999, page 1.
- W.C. Deese, Chem 13 News, Warnings to all demonstrators, May 1998, page 3.
John J. Fortman, A.C. Rush and J.E. Stamper, Journal of Chemical Education, Variations on the "Whoosh" Bottle Alcohol Explosion Demonstration Including Safety Notes, August 1999, pages 1092-1094.
