Australia's Science Forum

Not sure if this has already been covered. If it has please forgive me. Does any one do pracs where flammable liquids are set alight? A teacher here plans to do a 'burning things' prac and Im a bit unsure because I haven't come across burning of petrol, diesel, metho and kero in the labs before. I expect this needs to be done with great care! I am still trying to assertain this particular teachers level of experience - he assures me he has done it before and it is a 'piece of cake'.
Joy

hi joy,
If I am in doubt as to the safety of the prac and cannot find something that says "this is banned in schools" or "must be done in fume hood" then I go to the head of science voice my concerns and ask his opinion. I figure if he says it's ok then it's on his head if something goes wrong. I know I am passing the buck, and it isnt very good if the kids all get blown up but I dont think we should have the responsibility of incompetent teachers thrust upon us. We dont get paid enough for that!!
Cheers Jen

Hi Joy
Why not use spirit burners smelly but safer.
Noona

One of my teachers did this by pouring a small volume of the liquid into an evaporating basin and throwing a lit match into it. This was done on the teacher's bench at the front of the lab with all the kids back behind the second row. I thought it was a bad idea, but this teacher has been at this school forever (and is retiring next term) and said there was never any problem... and there wasn't.
The HT said it was up to the teacher to decide whether or not to do it.
I still think it is a dangerous practise and I don't see why it is necessary - he also uses the spirit burners for the heat energy prac.

Carol

Petrol is explosive, so I'd say no to that one, but the others are ok, especially if done in a spirit burner. We have lit metho in a watch glass before, but not the other ones you mentioned.

After talking to my firefighter hubby I have decided to supply extra long matches! That's about all I can do - the rest is going to be up to the teacher. The main danger I can see is the lighting of the fuels and the possibility of them being knocked over. Some fuels are going to be placed in crucibles, others in watch glasses. We don't have spirit burners. This will all be taking place on my day off so I won't be able to hang around with the fire blanket ready!
Joy

Some of our senior classes did a burning of fuels prac last year. This involved having at least two heatproof mats beneath the crucible because of the heat given off. Each group had dropper bottles with the following liquids: methylated spirits, kerosene, paraffin liquid and I think mineral turpentine (absolutely no petrol). They placed a wad of cotton wool in the base of the crucible and added the fuel using a 10ml measuring cylinder. They had to make sure that the dropper bottle lids were tightened and placed away from the burning area. They then lit the fuel saturated cotton wool in the crucible and observed what happened. We found that it was better to do the burning of the kerosene and the paraffin oil in the open air as there was a lot of smoke and fumes given off (no fume cupboard in our physics lab). Done in controlled circumstances it worked well. This prac was different to the year 12 prac which uses spirit burners.
Lyn.
PS. Definitely not a suitable practical for junior classes. Should be done as a teacher demonstration.

Does anyone still use spirit burners for junior classes?if so what fuels do you use?
I ran it through risk assess and it said that students should be kept back from burners or behind a perspex shield!
It also recommended that if fuels are needed that metaldehyde or hexamine tablets are used.
It did not say it was outright banned, but it does seem to have a few concerns.

We have used alcohol (ethyl) and kero, but kero is not particularly nice as far as fumes and toxicity goes.

Any suggestions for alternatives?

The fumes alone would knock me out for the day.
We used to do the burning of alcohols etc. on watch glasses. Metho, kerosene, methanol, ethanol, until a student put her hand on the burning methanol or ethanol which wasn't visible while burning. Ever seen those race car drivers running around after an accident waving their arms in the air like they are possessed. It's just that you can't see the burning fluid on them.

Plus if any is spilt on the benches then it is too hard too see until it is on fire as well. Too dangerous for junior students.

I'd be careful with petrol, I've seen some awful burns from that exploding and burning people, not at school though. I think the vapours from most of the ones you mentioned are flammable aren't they.
If they say, trust me I'm a teacher.... Don't!!

We only do it in spirit burners!
After producing ethanol from yeast & Sugar, teacher poured onto watch glass and set alight after a couple of minutes watch glass shattered and fire ran over teachers desk.
Easily put out but sent warnings to only use very small quanties

We use spirit burners fairly frequently in the Junior classes.
According to CSIS they may use Ethanol, Pronanol, butanol and Methylated Spirits. Not methanol as that is 11-12.
Kerosene is toooooooooooooooo smelly and petrol is a teacher only

They are used a lot to demonstrate Dependant and Independant variables and fuel comparisons.
Incidentally I have an order for Year 10 tomorrow for them and have 3/4 spirit burners of each labelled with the appropriate fuels in the Flammables cabinet.

Joy wrote: Some fuels are going to be placed in crucibles, others in watch glasses. We don't have spirit burners.
Joy

We have some "home made" spirit burners here. They are made out of glass vials. a piece of class tube is pushed through a cork in the top and then venetian blind cord pushed through the tube for a wick. They are a little unstable, but could be made very stable by setting the vial in a small "sandwich tuna" tin with plaster of paris.

(Just an idea for making cheap spirit burners.)

Ian