shaman202
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ice bath question.
what would dissipate heat from a flask faster, isopropyl alcohol chilled at -19c or 1:3 salt water mixture chilled at -19c?
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Bot0nist
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I imagine the isopropyl, but it will warm up faster than than the NaCl + ice-water. How are you keeping the alcohol cold? Try acetone/dry ice if you
need it really cold, really fast.
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shaman202
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by using a deep freezer at -20c.
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Bot0nist
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I meant how do you maintain the temp of the alcohol after removing it from the freezer? Unless you let the reactions run in the freezer, I imagine the
isopropyl would warm up to room temp rather quickly, unless well insulated.
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shaman202
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you perform the reaction in the freezer.
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Bot0nist
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Do a quick experiment. Get 3 test tubes and fill them with 15ml of salt water. Measure the temperature in each test tube and record. Submerge one in
iso, one in salt water, and just set the third in the freezer air for a control. Leave them all for a specific amount of time and then measure the
temperature drop over time.
If you can get temp decrease/time for each method repeatedly then you will know for sure, regardless of what anyone tells you here.
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shaman202
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very smart idea. i shall do that.
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Bot0nist
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That's the joy of the scientific method my friend. Start with a question, form an educated guess as to what you think the answer will be, understand
the variables, and preform meaningful experiments to determine the facts.
This is the way to understand the world around us.
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Panache
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you will need to do each at least three times, so nine tests tubes, then average the results, one result is meaningless, as in it literally has no
scientific meaning
[Edited on 24-3-2011 by Panache]
Sorry for this edit, edited instead of quoting.
[Edited on 24-3-11 by woelen]
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Bot0nist
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@Panache
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"If you can get temp decrease/time for each method repeatedly then you will know for sure, regardless of what anyone tells you here."
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One hundred time would be better. Average them together.
[Edited on 24-3-2011 by Bot0nist]
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woelen
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Quote: Originally posted by Panache  | you will need to do each at least three times, so nine tests tubes, then average the results, one result is meaningless, as in it literally has no
scientific meaning
[Edited on 24-3-2011 by Panache] |
What you say is not true. One result also has a meaning, but repeating and
averaging numerical outcomes establishes the meaning more firmly.
So, yes, it is good to repeat an experiment and take average results, but saying that the outcome of a single experiment has no meaning is too bald.
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Panache
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| Quote: Originally posted by woelen | | Quote: Originally posted by Panache | you will need to do each at least three times, so nine tests tubes, then average the results, one result is meaningless, as in it literally has no
scientific meaning
[Edited on 24-3-2011 by Panache] |
What you say is not true. One result also has a meaning, but repeating and
averaging numerical outcomes establishes the meaning more firmly.
So, yes, it is good to repeat an experiment and take average results, but saying that the outcome of a single experiment has no meaning is too bald.
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yes you are correct in many respects and your expression 'too bald' is excellent for the criticism (english is your second language isn't it, reading
this succinct, yet accurate, metaphorical use of english of yours made me feel like i did every time i heard Kofi Anan speak, a bit mediocre as it was
far better than what i would have come up with and me with english as my first language.)
What i will now say, in revision, is that a numerical data point without confidence limits is scientifically meaningless and confidence limits can
only be determined by at least three replicates of the same conditions.
I read recently that part of the problem communicating climate science to the public lies within the use of the expression, uncertainty. People versed
is scientific language understand innately what is referred to however the public just see the use of this expression as 'they don't really know'. An
understandable confusion.
Also odd is the protocol adopted by organic chemists when quoting %yield, its simply the best yield obtained in any particular run. This can be highly
misleading. If data exists for multiple runs it should be protocol to include it.
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