"Sooty" Bunsens

[merilyn]

The new teacher has commented that the bunsens are the "sootiest" he's ever encountered. Every time his classes (mostly Year 7) use the bunsens the glassware comes out black and covered in soot.
However, the two teachers that have used that lab in the past have never had a problem. The bunsens in the other five labs (which are identical) don't cause a problem.
I have my suspicions, but am keeping an open mind waiting for your replies.

[dime]

Its not the bunsens but the way they are used. If the hole is not opened to let in the oxygen, it will blacken the glassware. Got to have a clean blue flame, no yellow or orange in it. Try one yourself, and then you can tell him.

[merilyn]

That's what I thought too, but he is in denial. Interestingly their first couple of pracs involved using a yellow flame to show that it doesn't heat water only causes the beaker to go black. They have since moved on to "real" pracs.
But, I'm still trying to keep an open mind

[RosalieM]

Perhaps the kids are lighting them on safety flame with the bunsen under the glassware which means before they turn it to the heating flame the beaker will go black. Then they probably return it to safety flame before turning off and without taking it out from under the beaker, again allowing more soot to be deposited. Just an idea?

[sunray18]

agree with you Roslaie. One of our teachers i telling the students to do it this way. Sooty beakers are the result! grr

[merilyn]

Thanks, guys for your input. I thought that that may have been the problem as no one else has experienced this, but wanted to make sure there wasn't some other problem I was unaware of. I'm in a tricky spot with this one and may just have to put up with black beakers until I find a tactful way of telling him. Probably wait until the next time he brings it up.

[RosalieM]

I tell the teachers that getting the black off glassware is part of the kids' washing up process. I get cranky when sooty glassware comes back! It wipes off easily with a cloth and when each person does one it is quick but when one person does a class full, not so quick!

[Ian]

Merilyn,
Have a quick "whiz around" and check a good sample of them yourself, just to be certain that there is NOT a problem. If you can get a good blue flame on each of them, or preferably a light blue cone in the middle of the blue flame, then ask him to show you which were the sooty bunsens. Make sure that you have a CLEAN beaker of water to heat up, not a sooty beaker.
Remember, we are just dumb school assistants, and he is the Scientist. A good scientist should be able to replicate his/her experiment.
If the beaker remains clean, proving that there is NOT a problem with the bunsens, then give him some rags and ask him to get his class to clean up their beakers as they SHOULD have done after their experiment!

Cheers

Ian