how does a boiling chip work?
- Thread starter chiddler
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It creates an area of imperfections for gases to collect and start boiling. In perfectly clean smooth glassware there is nowhere for gas bubbles to start forming when at boiling temp, so you might super-heat your liquid and still not get it to boil. The boiling chip helps the solution begin boiling.
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When the vapor pressure above your liquid and your atmospheric pressure are equal then you solution starts to boil right? So how does that happen? well, gas from your liquid develops and collects in cracks and small imperfections on the container walls. If there is nowhere in your container for gasses to collect, there will be no bubbles.
You can try this ( I don't recommend it) by heating water in a brand new lab beaker in the microwave. You can heat it up so much that it actually many degrees above actual boiling temperature without boiling. This is called a super-heated liquid.
https://www.youtube.com/watch?v=HKC37PoELbo
Once you add a small imperfection, like say a spoon, your liquid immediately boils violently.
This same concept can be applied to freezing liquids. Liquids usually need a small imperfection or a starter crystal to begin crystallization. You can test this by leaving unopened filtered spring-water water bottles outside on a cold night. It can be below freezing and the liquid will be still liquid until you shake it or introduce an imperfection.
In short a boiling chip is just a place for gas to collect in your liquid so that you can do reflux or so you can do whatever lab-thing you need to do.
This isn't really all that important for the MCAT.
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deleted103644
Read Cat's Cradle. And start having nightmares about Ice IX. (Although I think it would have to be Ice XX or so by now - Ice IX has been defined, but it's far less apocalyptic.)
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What makes you say that? I've seen questions at least half a dozen questions about boiling chips on practice material so far.
Anything used in a basic chemistry lab could possibly show up on the mcat.
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deleted103644
Here's another way of picturing it. Imagine two identical apartment buildings next to each other. You've moved into the one on the left just because the rent was cheaper.
Now they've started raising the rent in your building, so you're paying $5 a month more than rents in the other building. Do you move? Probably not, you're happy enough where you are and it isn't a huge difference - maybe if the rent in the building on the right were $100/month cheaper.
But if you were kicked out of your apartment (say by a giant rock falling into it), you would be free to choose the other building.
Yay for anthropomorphic descriptions.
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deleted103644
It disrupts the stability of the water molecules in liquid form. Water is a very organized liquid, it's the source of things like surface tension, etc. disrupting that makes it much easier for it to switch to a gaseous state.
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Oh, I know what a boiling chip does. I was asking about why he thinks it isn't important for MCAT.
There was mention of another type of thing that basically acts as a boiling chip, but I can't remember what it's called. Starts with an "e" I think.
Edit: Ebulliator.
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deleted103644
The flip side of a boiling stone is seeding for crystallization. That's more interesting in my opinion, but on some level it's all the same concept.
I doubt the MCAT will go too far in depth here since this is really physical chemistry (in fact a good chunk of p chem is about phase changes). If it did, the information would be provided in the caption.
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Yea, I've just seen at least one question where they told you that an ebulliator was used to introduce small air bubbles into the distillation system. Then there was a question that asked what the ebulliator likely was for.
To answer correctly you had to recognize that it was acting exactly like a boiling chip, and that boiling chips prevent superheating. Pretty tough question imo.
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Sorry, I didn't mean to say that it wouldn't be on the MCAT, I just think it is such a basic concept that there is very little they could ask that isn't obvious or a trick... but I supposed they have asked dumber and easier questions on the AAMC practice tests.
I work full time in a research lab for the past 4 years. Some of the basic science stuff where they ask something like "Why did they use so and so as a control?" are just so painfully obvious, that I forget that some people may not have as much experience with that stuff,
I work full time in a research lab for the past 4 years. Some of the basic science stuff where they ask something like "Why did they use so and so as a control?" are just so painfully obvious, that I forget that some people may not have as much experience with that stuff,
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I know how you feel. I've been working in a microbiology lab for the past ~15 months so all the micro questions and even related clinical/diagnostic techniques seem very very simple. I was thrown off by the problem about the ebulliator because I had completely forgotten about boiling chips. Also I hadn't seen boiling chips mentioned in any of my review materials, probably because I hadn't gone over lab techniques yet.
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I was making pasta last night and noticed my water was taking much longer than normal to boil. I was impatient so I decided to just throw the pasta in anyway and when I did, I almost splashed boiling water on myself. Somehow the water had superheated! It was pretty cool and made me think of this thread 😀
